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lguest: fix comment style

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I don't really notice it (except to begrudge the extra vertical
space), but Ingo does.  And he pointed out that one excuse of lguest
is as a teaching tool, it should set a good example.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@redhat.com>
This commit is contained in:
Rusty Russell
2009-07-30 16:03:45 -06:00
parent e969fed542
commit 2e04ef7691
17 changed files with 1906 additions and 1015 deletions
Download Patch File Download Diff File Expand all files Collapse all files

428
arch/x86/lguest/boot.c
View File

@@ -22,7 +22,8 @@
*
* So how does the kernel know it's a Guest? We'll see that later, but let's
* just say that we end up here where we replace the native functions various
* "paravirt" structures with our Guest versions, then boot like normal. :*/
* "paravirt" structures with our Guest versions, then boot like normal.
:*/
/*
* Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation.
@@ -74,7 +75,8 @@
*
* The Guest in our tale is a simple creature: identical to the Host but
* behaving in simplified but equivalent ways. In particular, the Guest is the
* same kernel as the Host (or at least, built from the same source code). :*/
* same kernel as the Host (or at least, built from the same source code).
:*/
struct lguest_data lguest_data = {
.hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF },
@@ -85,7 +87,8 @@ struct lguest_data lguest_data = {
.syscall_vec = SYSCALL_VECTOR,
};
/*G:037 async_hcall() is pretty simple: I'm quite proud of it really. We have a
/*G:037
* async_hcall() is pretty simple: I'm quite proud of it really. We have a
* ring buffer of stored hypercalls which the Host will run though next time we
* do a normal hypercall. Each entry in the ring has 5 slots for the hypercall
* arguments, and a "hcall_status" word which is 0 if the call is ready to go,
@@ -94,7 +97,8 @@ struct lguest_data lguest_data = {
* If we come around to a slot which hasn't been finished, then the table is
* full and we just make the hypercall directly. This has the nice side
* effect of causing the Host to run all the stored calls in the ring buffer
* which empties it for next time! */
* which empties it for next time!
*/
static void async_hcall(unsigned long call, unsigned long arg1,
unsigned long arg2, unsigned long arg3,
unsigned long arg4)
@@ -103,9 +107,11 @@ static void async_hcall(unsigned long call, unsigned long arg1,
static unsigned int next_call;
unsigned long flags;
/* Disable interrupts if not already disabled: we don't want an
/*
* Disable interrupts if not already disabled: we don't want an
* interrupt handler making a hypercall while we're already doing
* one! */
* one!
*/
local_irq_save(flags);
if (lguest_data.hcall_status[next_call] != 0xFF) {
/* Table full, so do normal hcall which will flush table. */
@@ -125,8 +131,9 @@ static void async_hcall(unsigned long call, unsigned long arg1,
local_irq_restore(flags);
}
/*G:035 Notice the lazy_hcall() above, rather than hcall(). This is our first
* real optimization trick!
/*G:035
* Notice the lazy_hcall() above, rather than hcall(). This is our first real
* optimization trick!
*
* When lazy_mode is set, it means we're allowed to defer all hypercalls and do
* them as a batch when lazy_mode is eventually turned off. Because hypercalls
@@ -136,7 +143,8 @@ static void async_hcall(unsigned long call, unsigned long arg1,
* lguest_leave_lazy_mode().
*
* So, when we're in lazy mode, we call async_hcall() to store the call for
* future processing: */
* future processing:
*/
static void lazy_hcall1(unsigned long call,
unsigned long arg1)
{
@@ -208,9 +216,11 @@ static void lguest_end_context_switch(struct task_struct *next)
* check there before it tries to deliver an interrupt.
*/
/* save_flags() is expected to return the processor state (ie. "flags"). The
/*
* save_flags() is expected to return the processor state (ie. "flags"). The
* flags word contains all kind of stuff, but in practice Linux only cares
* about the interrupt flag. Our "save_flags()" just returns that. */
* about the interrupt flag. Our "save_flags()" just returns that.
*/
static unsigned long save_fl(void)
{
return lguest_data.irq_enabled;
@@ -222,13 +232,15 @@ static void irq_disable(void)
lguest_data.irq_enabled = 0;
}
/* Let's pause a moment. Remember how I said these are called so often?
/*
* Let's pause a moment. Remember how I said these are called so often?
* Jeremy Fitzhardinge optimized them so hard early in 2009 that he had to
* break some rules. In particular, these functions are assumed to save their
* own registers if they need to: normal C functions assume they can trash the
* eax register. To use normal C functions, we use
* PV_CALLEE_SAVE_REGS_THUNK(), which pushes %eax onto the stack, calls the
* C function, then restores it. */
* C function, then restores it.
*/
PV_CALLEE_SAVE_REGS_THUNK(save_fl);
PV_CALLEE_SAVE_REGS_THUNK(irq_disable);
/*:*/
@@ -237,18 +249,20 @@ PV_CALLEE_SAVE_REGS_THUNK(irq_disable);
extern void lg_irq_enable(void);
extern void lg_restore_fl(unsigned long flags);
/*M:003 Note that we don't check for outstanding interrupts when we re-enable
* them (or when we unmask an interrupt). This seems to work for the moment,
* since interrupts are rare and we'll just get the interrupt on the next timer
* tick, but now we can run with CONFIG_NO_HZ, we should revisit this. One way
* would be to put the "irq_enabled" field in a page by itself, and have the
* Host write-protect it when an interrupt comes in when irqs are disabled.
* There will then be a page fault as soon as interrupts are re-enabled.
/*M:003
* Note that we don't check for outstanding interrupts when we re-enable them
* (or when we unmask an interrupt). This seems to work for the moment, since
* interrupts are rare and we'll just get the interrupt on the next timer tick,
* but now we can run with CONFIG_NO_HZ, we should revisit this. One way would
* be to put the "irq_enabled" field in a page by itself, and have the Host
* write-protect it when an interrupt comes in when irqs are disabled. There
* will then be a page fault as soon as interrupts are re-enabled.
*
* A better method is to implement soft interrupt disable generally for x86:
* instead of disabling interrupts, we set a flag. If an interrupt does come
* in, we then disable them for real. This is uncommon, so we could simply use
* a hypercall for interrupt control and not worry about efficiency. :*/
* a hypercall for interrupt control and not worry about efficiency.
:*/
/*G:034
* The Interrupt Descriptor Table (IDT).
@@ -261,10 +275,12 @@ extern void lg_restore_fl(unsigned long flags);
static void lguest_write_idt_entry(gate_desc *dt,
int entrynum, const gate_desc *g)
{
/* The gate_desc structure is 8 bytes long: we hand it to the Host in
/*
* The gate_desc structure is 8 bytes long: we hand it to the Host in
* two 32-bit chunks. The whole 32-bit kernel used to hand descriptors
* around like this; typesafety wasn't a big concern in Linux's early
* years. */
* years.
*/
u32 *desc = (u32 *)g;
/* Keep the local copy up to date. */
native_write_idt_entry(dt, entrynum, g);
@@ -272,9 +288,11 @@ static void lguest_write_idt_entry(gate_desc *dt,
kvm_hypercall3(LHCALL_LOAD_IDT_ENTRY, entrynum, desc[0], desc[1]);
}
/* Changing to a different IDT is very rare: we keep the IDT up-to-date every
/*
* Changing to a different IDT is very rare: we keep the IDT up-to-date every
* time it is written, so we can simply loop through all entries and tell the
* Host about them. */
* Host about them.
*/
static void lguest_load_idt(const struct desc_ptr *desc)
{
unsigned int i;
@@ -305,9 +323,11 @@ static void lguest_load_gdt(const struct desc_ptr *desc)
kvm_hypercall3(LHCALL_LOAD_GDT_ENTRY, i, gdt[i].a, gdt[i].b);
}
/* For a single GDT entry which changes, we do the lazy thing: alter our GDT,
/*
* For a single GDT entry which changes, we do the lazy thing: alter our GDT,
* then tell the Host to reload the entire thing. This operation is so rare
* that this naive implementation is reasonable. */
* that this naive implementation is reasonable.
*/
static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum,
const void *desc, int type)
{
@@ -317,29 +337,36 @@ static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum,
dt[entrynum].a, dt[entrynum].b);
}
/* OK, I lied. There are three "thread local storage" GDT entries which change
/*
* OK, I lied. There are three "thread local storage" GDT entries which change
* on every context switch (these three entries are how glibc implements
* __thread variables). So we have a hypercall specifically for this case. */
* __thread variables). So we have a hypercall specifically for this case.
*/
static void lguest_load_tls(struct thread_struct *t, unsigned int cpu)
{
/* There's one problem which normal hardware doesn't have: the Host
/*
* There's one problem which normal hardware doesn't have: the Host
* can't handle us removing entries we're currently using. So we clear
* the GS register here: if it's needed it'll be reloaded anyway. */
* the GS register here: if it's needed it'll be reloaded anyway.
*/
lazy_load_gs(0);
lazy_hcall2(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu);
}
/*G:038 That's enough excitement for now, back to ploughing through each of
* the different pv_ops structures (we're about 1/3 of the way through).
/*G:038
* That's enough excitement for now, back to ploughing through each of the
* different pv_ops structures (we're about 1/3 of the way through).
*
* This is the Local Descriptor Table, another weird Intel thingy. Linux only
* uses this for some strange applications like Wine. We don't do anything
* here, so they'll get an informative and friendly Segmentation Fault. */
* here, so they'll get an informative and friendly Segmentation Fault.
*/
static void lguest_set_ldt(const void *addr, unsigned entries)
{
}
/* This loads a GDT entry into the "Task Register": that entry points to a
/*
* This loads a GDT entry into the "Task Register": that entry points to a
* structure called the Task State Segment. Some comments scattered though the
* kernel code indicate that this used for task switching in ages past, along
* with blood sacrifice and astrology.
@@ -347,19 +374,21 @@ static void lguest_set_ldt(const void *addr, unsigned entries)
* Now there's nothing interesting in here that we don't get told elsewhere.
* But the native version uses the "ltr" instruction, which makes the Host
* complain to the Guest about a Segmentation Fault and it'll oops. So we
* override the native version with a do-nothing version. */
* override the native version with a do-nothing version.
*/
static void lguest_load_tr_desc(void)
{
}
/* The "cpuid" instruction is a way of querying both the CPU identity
/*
* The "cpuid" instruction is a way of querying both the CPU identity
* (manufacturer, model, etc) and its features. It was introduced before the
* Pentium in 1993 and keeps getting extended by both Intel, AMD and others.
* As you might imagine, after a decade and a half this treatment, it is now a
* giant ball of hair. Its entry in the current Intel manual runs to 28 pages.
*
* This instruction even it has its own Wikipedia entry. The Wikipedia entry
* has been translated into 4 languages. I am not making this up!
* has been translated into 5 languages. I am not making this up!
*
* We could get funky here and identify ourselves as "GenuineLguest", but
* instead we just use the real "cpuid" instruction. Then I pretty much turned
@@ -371,7 +400,8 @@ static void lguest_load_tr_desc(void)
* Replacing the cpuid so we can turn features off is great for the kernel, but
* anyone (including userspace) can just use the raw "cpuid" instruction and
* the Host won't even notice since it isn't privileged. So we try not to get
* too worked up about it. */
* too worked up about it.
*/
static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
unsigned int *cx, unsigned int *dx)
{
@@ -379,43 +409,63 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
native_cpuid(ax, bx, cx, dx);
switch (function) {
case 0: /* ID and highest CPUID. Futureproof a little by sticking to
* older ones. */
/*
* CPUID 0 gives the highest legal CPUID number (and the ID string).
* We futureproof our code a little by sticking to known CPUID values.
*/
case 0:
if (*ax > 5)
*ax = 5;
break;
case 1: /* Basic feature request. */
/* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */
/*
* CPUID 1 is a basic feature request.
*
* CX: we only allow kernel to see SSE3, CMPXCHG16B and SSSE3
* DX: SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU and PAE.
*/
case 1:
*cx &= 0x00002201;
/* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU, PAE. */
*dx &= 0x07808151;
/* The Host can do a nice optimization if it knows that the
/*
* The Host can do a nice optimization if it knows that the
* kernel mappings (addresses above 0xC0000000 or whatever
* PAGE_OFFSET is set to) haven't changed. But Linux calls
* flush_tlb_user() for both user and kernel mappings unless
* the Page Global Enable (PGE) feature bit is set. */
* the Page Global Enable (PGE) feature bit is set.
*/
*dx |= 0x00002000;
/* We also lie, and say we're family id 5. 6 or greater
/*
* We also lie, and say we're family id 5. 6 or greater
* leads to a rdmsr in early_init_intel which we can't handle.
* Family ID is returned as bits 8-12 in ax. */
* Family ID is returned as bits 8-12 in ax.
*/
*ax &= 0xFFFFF0FF;
*ax |= 0x00000500;
break;
/*
* 0x80000000 returns the highest Extended Function, so we futureproof
* like we do above by limiting it to known fields.
*/
case 0x80000000:
/* Futureproof this a little: if they ask how much extended
* processor information there is, limit it to known fields. */
if (*ax > 0x80000008)
*ax = 0x80000008;
break;
/*
* PAE systems can mark pages as non-executable. Linux calls this the
* NX bit. Intel calls it XD (eXecute Disable), AMD EVP (Enhanced
* Virus Protection). We just switch turn if off here, since we don't
* support it.
*/
case 0x80000001:
/* Here we should fix nx cap depending on host. */
/* For this version of PAE, we just clear NX bit. */
*dx &= ~(1 << 20);
break;
}
}
/* Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4.
/*
* Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4.
* I assume there's a cr1, but it hasn't bothered us yet, so we'll not bother
* it. The Host needs to know when the Guest wants to change them, so we have
* a whole series of functions like read_cr0() and write_cr0().
@@ -430,7 +480,8 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
* name like "FPUTRAP bit" be a little less cryptic?
*
* We store cr0 locally because the Host never changes it. The Guest sometimes
* wants to read it and we'd prefer not to bother the Host unnecessarily. */
* wants to read it and we'd prefer not to bother the Host unnecessarily.
*/
static unsigned long current_cr0;
static void lguest_write_cr0(unsigned long val)
{
@@ -443,18 +494,22 @@ static unsigned long lguest_read_cr0(void)
return current_cr0;
}
/* Intel provided a special instruction to clear the TS bit for people too cool
/*
* Intel provided a special instruction to clear the TS bit for people too cool
* to use write_cr0() to do it. This "clts" instruction is faster, because all
* the vowels have been optimized out. */
* the vowels have been optimized out.
*/
static void lguest_clts(void)
{
lazy_hcall1(LHCALL_TS, 0);
current_cr0 &= ~X86_CR0_TS;
}
/* cr2 is the virtual address of the last page fault, which the Guest only ever
/*
* cr2 is the virtual address of the last page fault, which the Guest only ever
* reads. The Host kindly writes this into our "struct lguest_data", so we
* just read it out of there. */
* just read it out of there.
*/
static unsigned long lguest_read_cr2(void)
{
return lguest_data.cr2;
@@ -463,10 +518,12 @@ static unsigned long lguest_read_cr2(void)
/* See lguest_set_pte() below. */
static bool cr3_changed = false;
/* cr3 is the current toplevel pagetable page: the principle is the same as
/*
* cr3 is the current toplevel pagetable page: the principle is the same as
* cr0. Keep a local copy, and tell the Host when it changes. The only
* difference is that our local copy is in lguest_data because the Host needs
* to set it upon our initial hypercall. */
* to set it upon our initial hypercall.
*/
static void lguest_write_cr3(unsigned long cr3)
{
lguest_data.pgdir = cr3;
@@ -538,10 +595,12 @@ static void lguest_write_cr4(unsigned long val)
* the real page tables based on the Guests'.
*/
/* The Guest calls this to set a second-level entry (pte), ie. to map a page
/*
* The Guest calls this to set a second-level entry (pte), ie. to map a page
* into a process' address space. We set the entry then tell the Host the
* toplevel and address this corresponds to. The Guest uses one pagetable per
* process, so we need to tell the Host which one we're changing (mm->pgd). */
* process, so we need to tell the Host which one we're changing (mm->pgd).
*/
static void lguest_pte_update(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
@@ -560,10 +619,13 @@ static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr,
lguest_pte_update(mm, addr, ptep);
}
/* The Guest calls lguest_set_pud to set a top-level entry and lguest_set_pmd
/*
* The Guest calls lguest_set_pud to set a top-level entry and lguest_set_pmd
* to set a middle-level entry when PAE is activated.
*
* Again, we set the entry then tell the Host which page we changed,
* and the index of the entry we changed. */
* and the index of the entry we changed.
*/
#ifdef CONFIG_X86_PAE
static void lguest_set_pud(pud_t *pudp, pud_t pudval)
{
@@ -582,8 +644,7 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
}
#else
/* The Guest calls lguest_set_pmd to set a top-level entry when PAE is not
* activated. */
/* The Guest calls lguest_set_pmd to set a top-level entry when !PAE. */
static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
{
native_set_pmd(pmdp, pmdval);
@@ -592,7 +653,8 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
}
#endif
/* There are a couple of legacy places where the kernel sets a PTE, but we
/*
* There are a couple of legacy places where the kernel sets a PTE, but we
* don't know the top level any more. This is useless for us, since we don't
* know which pagetable is changing or what address, so we just tell the Host
* to forget all of them. Fortunately, this is very rare.
@@ -600,7 +662,8 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
* ... except in early boot when the kernel sets up the initial pagetables,
* which makes booting astonishingly slow: 1.83 seconds! So we don't even tell
* the Host anything changed until we've done the first page table switch,
* which brings boot back to 0.25 seconds. */
* which brings boot back to 0.25 seconds.
*/
static void lguest_set_pte(pte_t *ptep, pte_t pteval)
{
native_set_pte(ptep, pteval);
@@ -628,7 +691,8 @@ void lguest_pmd_clear(pmd_t *pmdp)
}
#endif
/* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
/*
* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
* native page table operations. On native hardware you can set a new page
* table entry whenever you want, but if you want to remove one you have to do
* a TLB flush (a TLB is a little cache of page table entries kept by the CPU).
@@ -637,24 +701,29 @@ void lguest_pmd_clear(pmd_t *pmdp)
* called when a valid entry is written, not when it's removed (ie. marked not
* present). Instead, this is where we come when the Guest wants to remove a
* page table entry: we tell the Host to set that entry to 0 (ie. the present
* bit is zero). */
* bit is zero).
*/
static void lguest_flush_tlb_single(unsigned long addr)
{
/* Simply set it to zero: if it was not, it will fault back in. */
lazy_hcall3(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
}
/* This is what happens after the Guest has removed a large number of entries.
/*
* This is what happens after the Guest has removed a large number of entries.
* This tells the Host that any of the page table entries for userspace might
* have changed, ie. virtual addresses below PAGE_OFFSET. */
* have changed, ie. virtual addresses below PAGE_OFFSET.
*/
static void lguest_flush_tlb_user(void)
{
lazy_hcall1(LHCALL_FLUSH_TLB, 0);
}
/* This is called when the kernel page tables have changed. That's not very
/*
* This is called when the kernel page tables have changed. That's not very
* common (unless the Guest is using highmem, which makes the Guest extremely
* slow), so it's worth separating this from the user flushing above. */
* slow), so it's worth separating this from the user flushing above.
*/
static void lguest_flush_tlb_kernel(void)
{
lazy_hcall1(LHCALL_FLUSH_TLB, 1);
@@ -691,23 +760,27 @@ static struct irq_chip lguest_irq_controller = {
.unmask = enable_lguest_irq,
};
/* This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
/*
* This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
* interrupt (except 128, which is used for system calls), and then tells the
* Linux infrastructure that each interrupt is controlled by our level-based
* lguest interrupt controller. */
* lguest interrupt controller.
*/
static void __init lguest_init_IRQ(void)
{
unsigned int i;
for (i = FIRST_EXTERNAL_VECTOR; i < NR_VECTORS; i++) {
/* Some systems map "vectors" to interrupts weirdly. Lguest has
* a straightforward 1 to 1 mapping, so force that here. */
/* Some systems map "vectors" to interrupts weirdly. Not us! */
__get_cpu_var(vector_irq)[i] = i - FIRST_EXTERNAL_VECTOR;
if (i != SYSCALL_VECTOR)
set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
}
/* This call is required to set up for 4k stacks, where we have
* separate stacks for hard and soft interrupts. */
/*
* This call is required to set up for 4k stacks, where we have
* separate stacks for hard and soft interrupts.
*/
irq_ctx_init(smp_processor_id());
}
@@ -729,31 +802,39 @@ static unsigned long lguest_get_wallclock(void)
return lguest_data.time.tv_sec;
}
/* The TSC is an Intel thing called the Time Stamp Counter. The Host tells us
/*
* The TSC is an Intel thing called the Time Stamp Counter. The Host tells us
* what speed it runs at, or 0 if it's unusable as a reliable clock source.
* This matches what we want here: if we return 0 from this function, the x86
* TSC clock will give up and not register itself. */
* TSC clock will give up and not register itself.
*/
static unsigned long lguest_tsc_khz(void)
{
return lguest_data.tsc_khz;
}
/* If we can't use the TSC, the kernel falls back to our lower-priority
* "lguest_clock", where we read the time value given to us by the Host. */
/*
* If we can't use the TSC, the kernel falls back to our lower-priority
* "lguest_clock", where we read the time value given to us by the Host.
*/
static cycle_t lguest_clock_read(struct clocksource *cs)
{
unsigned long sec, nsec;
/* Since the time is in two parts (seconds and nanoseconds), we risk
/*
* Since the time is in two parts (seconds and nanoseconds), we risk
* reading it just as it's changing from 99 & 0.999999999 to 100 and 0,
* and getting 99 and 0. As Linux tends to come apart under the stress
* of time travel, we must be careful: */
* of time travel, we must be careful:
*/
do {
/* First we read the seconds part. */
sec = lguest_data.time.tv_sec;
/* This read memory barrier tells the compiler and the CPU that
/*
* This read memory barrier tells the compiler and the CPU that
* this can't be reordered: we have to complete the above
* before going on. */
* before going on.
*/
rmb();
/* Now we read the nanoseconds part. */
nsec = lguest_data.time.tv_nsec;
@@ -777,9 +858,11 @@ static struct clocksource lguest_clock = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
/* We also need a "struct clock_event_device": Linux asks us to set it to go
/*
* We also need a "struct clock_event_device": Linux asks us to set it to go
* off some time in the future. Actually, James Morris figured all this out, I
* just applied the patch. */
* just applied the patch.
*/
static int lguest_clockevent_set_next_event(unsigned long delta,
struct clock_event_device *evt)
{
@@ -829,8 +912,10 @@ static struct clock_event_device lguest_clockevent = {
.max_delta_ns = LG_CLOCK_MAX_DELTA,
};
/* This is the Guest timer interrupt handler (hardware interrupt 0). We just
* call the clockevent infrastructure and it does whatever needs doing. */
/*
* This is the Guest timer interrupt handler (hardware interrupt 0). We just
* call the clockevent infrastructure and it does whatever needs doing.
*/
static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
{
unsigned long flags;
@@ -841,10 +926,12 @@ static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
local_irq_restore(flags);
}
/* At some point in the boot process, we get asked to set up our timing
/*
* At some point in the boot process, we get asked to set up our timing
* infrastructure. The kernel doesn't expect timer interrupts before this, but
* we cleverly initialized the "blocked_interrupts" field of "struct
* lguest_data" so that timer interrupts were blocked until now. */
* lguest_data" so that timer interrupts were blocked until now.
*/
static void lguest_time_init(void)
{
/* Set up the timer interrupt (0) to go to our simple timer routine */
@@ -868,14 +955,16 @@ static void lguest_time_init(void)
* to work. They're pretty simple.
*/
/* The Guest needs to tell the Host what stack it expects traps to use. For
/*
* The Guest needs to tell the Host what stack it expects traps to use. For
* native hardware, this is part of the Task State Segment mentioned above in
* lguest_load_tr_desc(), but to help hypervisors there's this special call.
*
* We tell the Host the segment we want to use (__KERNEL_DS is the kernel data
* segment), the privilege level (we're privilege level 1, the Host is 0 and
* will not tolerate us trying to use that), the stack pointer, and the number
* of pages in the stack. */
* of pages in the stack.
*/
static void lguest_load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
{
@@ -889,7 +978,8 @@ static void lguest_set_debugreg(int regno, unsigned long value)
/* FIXME: Implement */
}
/* There are times when the kernel wants to make sure that no memory writes are
/*
* There are times when the kernel wants to make sure that no memory writes are
* caught in the cache (that they've all reached real hardware devices). This
* doesn't matter for the Guest which has virtual hardware.
*
@@ -903,11 +993,13 @@ static void lguest_wbinvd(void)
{
}
/* If the Guest expects to have an Advanced Programmable Interrupt Controller,
/*
* If the Guest expects to have an Advanced Programmable Interrupt Controller,
* we play dumb by ignoring writes and returning 0 for reads. So it's no
* longer Programmable nor Controlling anything, and I don't think 8 lines of
* code qualifies for Advanced. It will also never interrupt anything. It
* does, however, allow us to get through the Linux boot code. */
* does, however, allow us to get through the Linux boot code.
*/
#ifdef CONFIG_X86_LOCAL_APIC
static void lguest_apic_write(u32 reg, u32 v)
{
@@ -956,11 +1048,13 @@ static void lguest_safe_halt(void)
kvm_hypercall0(LHCALL_HALT);
}
/* The SHUTDOWN hypercall takes a string to describe what's happening, and
/*
* The SHUTDOWN hypercall takes a string to describe what's happening, and
* an argument which says whether this to restart (reboot) the Guest or not.
*
* Note that the Host always prefers that the Guest speak in physical addresses
* rather than virtual addresses, so we use __pa() here. */
* rather than virtual addresses, so we use __pa() here.
*/
static void lguest_power_off(void)
{
kvm_hypercall2(LHCALL_SHUTDOWN, __pa("Power down"),
@@ -991,8 +1085,10 @@ static __init char *lguest_memory_setup(void)
* nice to move it back to lguest_init. Patch welcome... */
atomic_notifier_chain_register(&panic_notifier_list, &paniced);
/* The Linux bootloader header contains an "e820" memory map: the
* Launcher populated the first entry with our memory limit. */
/*
*The Linux bootloader header contains an "e820" memory map: the
* Launcher populated the first entry with our memory limit.
*/
e820_add_region(boot_params.e820_map[0].addr,
boot_params.e820_map[0].size,
boot_params.e820_map[0].type);
@@ -1001,16 +1097,17 @@ static __init char *lguest_memory_setup(void)
return "LGUEST";
}
/* We will eventually use the virtio console device to produce console output,
/*
* We will eventually use the virtio console device to produce console output,
* but before that is set up we use LHCALL_NOTIFY on normal memory to produce
* console output. */
* console output.
*/
static __init int early_put_chars(u32 vtermno, const char *buf, int count)
{
char scratch[17];
unsigned int len = count;
/* We use a nul-terminated string, so we have to make a copy. Icky,
* huh? */
/* We use a nul-terminated string, so we make a copy. Icky, huh? */
if (len > sizeof(scratch) - 1)
len = sizeof(scratch) - 1;
scratch[len] = '\0';
@@ -1021,8 +1118,10 @@ static __init int early_put_chars(u32 vtermno, const char *buf, int count)
return len;
}
/* Rebooting also tells the Host we're finished, but the RESTART flag tells the
* Launcher to reboot us. */
/*
* Rebooting also tells the Host we're finished, but the RESTART flag tells the
* Launcher to reboot us.
*/
static void lguest_restart(char *reason)
{
kvm_hypercall2(LHCALL_SHUTDOWN, __pa(reason), LGUEST_SHUTDOWN_RESTART);
@@ -1049,7 +1148,8 @@ static void lguest_restart(char *reason)
* fit comfortably.
*
* First we need assembly templates of each of the patchable Guest operations,
* and these are in i386_head.S. */
* and these are in i386_head.S.
*/
/*G:060 We construct a table from the assembler templates: */
static const struct lguest_insns
@@ -1060,9 +1160,11 @@ static const struct lguest_insns
[PARAVIRT_PATCH(pv_irq_ops.save_fl)] = { lgstart_pushf, lgend_pushf },
};
/* Now our patch routine is fairly simple (based on the native one in
/*
* Now our patch routine is fairly simple (based on the native one in
* paravirt.c). If we have a replacement, we copy it in and return how much of
* the available space we used. */
* the available space we used.
*/
static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
unsigned long addr, unsigned len)
{
@@ -1074,8 +1176,7 @@ static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
insn_len = lguest_insns[type].end - lguest_insns[type].start;
/* Similarly if we can't fit replacement (shouldn't happen, but let's
* be thorough). */
/* Similarly if it can't fit (doesn't happen, but let's be thorough). */
if (len < insn_len)
return paravirt_patch_default(type, clobber, ibuf, addr, len);
@@ -1084,22 +1185,28 @@ static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
return insn_len;
}
/*G:029 Once we get to lguest_init(), we know we're a Guest. The various
/*G:029
* Once we get to lguest_init(), we know we're a Guest. The various
* pv_ops structures in the kernel provide points for (almost) every routine we
* have to override to avoid privileged instructions. */
* have to override to avoid privileged instructions.
*/
__init void lguest_init(void)
{
/* We're under lguest, paravirt is enabled, and we're running at
* privilege level 1, not 0 as normal. */
/* We're under lguest. */
pv_info.name = "lguest";
/* Paravirt is enabled. */
pv_info.paravirt_enabled = 1;
/* We're running at privilege level 1, not 0 as normal. */
pv_info.kernel_rpl = 1;
/* Everyone except Xen runs with this set. */
pv_info.shared_kernel_pmd = 1;
/* We set up all the lguest overrides for sensitive operations. These
* are detailed with the operations themselves. */
/*
* We set up all the lguest overrides for sensitive operations. These
* are detailed with the operations themselves.
*/
/* interrupt-related operations */
/* Interrupt-related operations */
pv_irq_ops.init_IRQ = lguest_init_IRQ;
pv_irq_ops.save_fl = PV_CALLEE_SAVE(save_fl);
pv_irq_ops.restore_fl = __PV_IS_CALLEE_SAVE(lg_restore_fl);
@@ -1107,11 +1214,11 @@ __init void lguest_init(void)
pv_irq_ops.irq_enable = __PV_IS_CALLEE_SAVE(lg_irq_enable);
pv_irq_ops.safe_halt = lguest_safe_halt;
/* init-time operations */
/* Setup operations */
pv_init_ops.memory_setup = lguest_memory_setup;
pv_init_ops.patch = lguest_patch;
/* Intercepts of various cpu instructions */
/* Intercepts of various CPU instructions */
pv_cpu_ops.load_gdt = lguest_load_gdt;
pv_cpu_ops.cpuid = lguest_cpuid;
pv_cpu_ops.load_idt = lguest_load_idt;
@@ -1132,7 +1239,7 @@ __init void lguest_init(void)
pv_cpu_ops.start_context_switch = paravirt_start_context_switch;
pv_cpu_ops.end_context_switch = lguest_end_context_switch;
/* pagetable management */
/* Pagetable management */
pv_mmu_ops.write_cr3 = lguest_write_cr3;
pv_mmu_ops.flush_tlb_user = lguest_flush_tlb_user;
pv_mmu_ops.flush_tlb_single = lguest_flush_tlb_single;
@@ -1154,54 +1261,71 @@ __init void lguest_init(void)
pv_mmu_ops.pte_update_defer = lguest_pte_update;
#ifdef CONFIG_X86_LOCAL_APIC
/* apic read/write intercepts */
/* APIC read/write intercepts */
set_lguest_basic_apic_ops();
#endif
/* time operations */
/* Time operations */
pv_time_ops.get_wallclock = lguest_get_wallclock;
pv_time_ops.time_init = lguest_time_init;
pv_time_ops.get_tsc_khz = lguest_tsc_khz;
/* Now is a good time to look at the implementations of these functions
* before returning to the rest of lguest_init(). */
/*
* Now is a good time to look at the implementations of these functions
* before returning to the rest of lguest_init().
*/
/*G:070 Now we've seen all the paravirt_ops, we return to
/*G:070
* Now we've seen all the paravirt_ops, we return to
* lguest_init() where the rest of the fairly chaotic boot setup
* occurs. */
* occurs.
*/
/* The stack protector is a weird thing where gcc places a canary
/*
* The stack protector is a weird thing where gcc places a canary
* value on the stack and then checks it on return. This file is
* compiled with -fno-stack-protector it, so we got this far without
* problems. The value of the canary is kept at offset 20 from the
* %gs register, so we need to set that up before calling C functions
* in other files. */
* in other files.
*/
setup_stack_canary_segment(0);
/* We could just call load_stack_canary_segment(), but we might as
* call switch_to_new_gdt() which loads the whole table and sets up
* the per-cpu segment descriptor register %fs as well. */
/*
* We could just call load_stack_canary_segment(), but we might as well
* call switch_to_new_gdt() which loads the whole table and sets up the
* per-cpu segment descriptor register %fs as well.
*/
switch_to_new_gdt(0);
/* As described in head_32.S, we map the first 128M of memory. */
max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
/* The Host<->Guest Switcher lives at the top of our address space, and
/*
* The Host<->Guest Switcher lives at the top of our address space, and
* the Host told us how big it is when we made LGUEST_INIT hypercall:
* it put the answer in lguest_data.reserve_mem */
* it put the answer in lguest_data.reserve_mem
*/
reserve_top_address(lguest_data.reserve_mem);
/* If we don't initialize the lock dependency checker now, it crashes
* paravirt_disable_iospace. */
/*
* If we don't initialize the lock dependency checker now, it crashes
* paravirt_disable_iospace.
*/
lockdep_init();
/* The IDE code spends about 3 seconds probing for disks: if we reserve
/*
* The IDE code spends about 3 seconds probing for disks: if we reserve
* all the I/O ports up front it can't get them and so doesn't probe.
* Other device drivers are similar (but less severe). This cuts the
* kernel boot time on my machine from 4.1 seconds to 0.45 seconds. */
* kernel boot time on my machine from 4.1 seconds to 0.45 seconds.
*/
paravirt_disable_iospace();
/* This is messy CPU setup stuff which the native boot code does before
* start_kernel, so we have to do, too: */
/*
* This is messy CPU setup stuff which the native boot code does before
* start_kernel, so we have to do, too:
*/
cpu_detect(&new_cpu_data);
/* head.S usually sets up the first capability word, so do it here. */
new_cpu_data.x86_capability[0] = cpuid_edx(1);
@@ -1218,22 +1342,28 @@ __init void lguest_init(void)
acpi_ht = 0;
#endif
/* We set the preferred console to "hvc". This is the "hypervisor
/*
* We set the preferred console to "hvc". This is the "hypervisor
* virtual console" driver written by the PowerPC people, which we also
* adapted for lguest's use. */
* adapted for lguest's use.
*/
add_preferred_console("hvc", 0, NULL);
/* Register our very early console. */
virtio_cons_early_init(early_put_chars);
/* Last of all, we set the power management poweroff hook to point to
/*
* Last of all, we set the power management poweroff hook to point to
* the Guest routine to power off, and the reboot hook to our restart
* routine. */
* routine.
*/
pm_power_off = lguest_power_off;
machine_ops.restart = lguest_restart;
/* Now we're set up, call i386_start_kernel() in head32.c and we proceed
* to boot as normal. It never returns. */
/*
* Now we're set up, call i386_start_kernel() in head32.c and we proceed
* to boot as normal. It never returns.
*/
i386_start_kernel();
}
/*