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Boot with virtual == physical to get closer to native Linux.

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1) This allows us to get alot closer to booting bzImages.

2) It means we don't have to know page_offset.

3) The Guest needs to modify the boot pagetables to create the
   PAGE_OFFSET mapping before jumping to C code.

4) guest_pa() walks the page tables rather than using page_offset.

5) We don't use page_offset to figure out whether to emulate: it was
   always kinda quesationable, and won't work for instructions done
   before remapping (bzImage unpacking in particular).

6) We still want the kernel address for tlb flushing: have the initial
   hypercall give us that, too.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2007-10-22 11:03:36 +10:00
parent c18acd73ff
commit 47436aa4ad
12 changed files with 141 additions and 148 deletions
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7
drivers/lguest/x86/core.c
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@@ -216,9 +216,10 @@ static int emulate_insn(struct lguest *lg)
* guest_pa just subtracts the Guest's page_offset. */
unsigned long physaddr = guest_pa(lg, lg->regs->eip);
/* The guest_pa() function only works for Guest kernel addresses, but
* that's all we're trying to do anyway. */
if (lg->regs->eip < lg->page_offset)
/* This must be the Guest kernel trying to do something, not userspace!
* The bottom two bits of the CS segment register are the privilege
* level. */
if ((lg->regs->cs & 3) != GUEST_PL)
return 0;
/* Decoding x86 instructions is icky. */