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KVM: Simply gfn_to_page()

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Mapping a guest page to a host page is a common operation.  Currently,
one has first to find the memory slot where the page belongs (gfn_to_memslot),
then locate the page itself (gfn_to_page()).

This is clumsy, and also won't work well with memory aliases.  So simplify
gfn_to_page() not to require memory slot translation first, and instead do it
internally.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity
2007-03-30 14:02:32 +03:00
parent e0fa826f96
commit 954bbbc236
4 changed files with 33 additions and 42 deletions
Download Patch File Download Diff File Expand all files Collapse all files

45
drivers/kvm/kvm_main.c
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@@ -420,12 +420,12 @@ static int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
u64 pdpte;
u64 *pdpt;
int ret;
struct kvm_memory_slot *memslot;
struct page *page;
spin_lock(&vcpu->kvm->lock);
memslot = gfn_to_memslot(vcpu->kvm, pdpt_gfn);
/* FIXME: !memslot - emulate? 0xff? */
pdpt = kmap_atomic(gfn_to_page(memslot, pdpt_gfn), KM_USER0);
page = gfn_to_page(vcpu->kvm, pdpt_gfn);
/* FIXME: !page - emulate? 0xff? */
pdpt = kmap_atomic(page, KM_USER0);
ret = 1;
for (i = 0; i < 4; ++i) {
@@ -861,6 +861,17 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_GPL(gfn_to_memslot);
struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
{
struct kvm_memory_slot *slot;
slot = gfn_to_memslot(kvm, gfn);
if (!slot)
return NULL;
return slot->phys_mem[gfn - slot->base_gfn];
}
EXPORT_SYMBOL_GPL(gfn_to_page);
void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
{
int i;
@@ -899,20 +910,20 @@ static int emulator_read_std(unsigned long addr,
unsigned offset = addr & (PAGE_SIZE-1);
unsigned tocopy = min(bytes, (unsigned)PAGE_SIZE - offset);
unsigned long pfn;
struct kvm_memory_slot *memslot;
void *page;
struct page *page;
void *page_virt;
if (gpa == UNMAPPED_GVA)
return X86EMUL_PROPAGATE_FAULT;
pfn = gpa >> PAGE_SHIFT;
memslot = gfn_to_memslot(vcpu->kvm, pfn);
if (!memslot)
page = gfn_to_page(vcpu->kvm, pfn);
if (!page)
return X86EMUL_UNHANDLEABLE;
page = kmap_atomic(gfn_to_page(memslot, pfn), KM_USER0);
page_virt = kmap_atomic(page, KM_USER0);
memcpy(data, page + offset, tocopy);
memcpy(data, page_virt + offset, tocopy);
kunmap_atomic(page, KM_USER0);
kunmap_atomic(page_virt, KM_USER0);
bytes -= tocopy;
data += tocopy;
@@ -963,16 +974,14 @@ static int emulator_read_emulated(unsigned long addr,
static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
unsigned long val, int bytes)
{
struct kvm_memory_slot *m;
struct page *page;
void *virt;
if (((gpa + bytes - 1) >> PAGE_SHIFT) != (gpa >> PAGE_SHIFT))
return 0;
m = gfn_to_memslot(vcpu->kvm, gpa >> PAGE_SHIFT);
if (!m)
page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
if (!page)
return 0;
page = gfn_to_page(m, gpa >> PAGE_SHIFT);
kvm_mmu_pre_write(vcpu, gpa, bytes);
mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT);
virt = kmap_atomic(page, KM_USER0);
@@ -2516,15 +2525,11 @@ static struct page *kvm_vm_nopage(struct vm_area_struct *vma,
{
struct kvm *kvm = vma->vm_file->private_data;
unsigned long pgoff;
struct kvm_memory_slot *slot;
struct page *page;
*type = VM_FAULT_MINOR;
pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
slot = gfn_to_memslot(kvm, pgoff);
if (!slot)
return NOPAGE_SIGBUS;
page = gfn_to_page(slot, pgoff);
page = gfn_to_page(kvm, pgoff);
if (!page)
return NOPAGE_SIGBUS;
get_page(page);