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KVM: MMU: emulated cmpxchg8b should be atomic on i386 

Emulate cmpxchg8b atomically on i386. This is required to avoid a guest
pte walker from seeing a splitted write.

[avi: make it compile]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Marcelo Tosatti 2007-12-12 10:46:12 -05:00 committed by Avi Kivity
parent 62b9abaaf8
commit 2bacc55c7c
1 changed files with 26 additions and 0 deletions
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26
drivers/kvm/x86.c
View File

@ -25,6 +25,7 @@
#include <linux/vmalloc.h>
#include <linux/module.h>
#include <linux/mman.h>
#include <linux/highmem.h>
#include <asm/uaccess.h>
#include <asm/msr.h>
@ -1674,6 +1675,31 @@ static int emulator_cmpxchg_emulated(unsigned long addr,
reported = 1;
printk(KERN_WARNING "kvm: emulating exchange as write\n");
}
#ifndef CONFIG_X86_64
/* guests cmpxchg8b have to be emulated atomically */
if (bytes == 8) {
gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, addr);
struct page *page;
char *addr;
u64 val;
if (gpa == UNMAPPED_GVA ||
(gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE)
goto emul_write;
if (((gpa + bytes - 1) & PAGE_MASK) != (gpa & PAGE_MASK))
goto emul_write;
val = *(u64 *)new;
page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
addr = kmap_atomic(page, KM_USER0);
set_64bit((u64 *)(addr + offset_in_page(gpa)), val);
kunmap_atomic(addr, KM_USER0);
kvm_release_page_dirty(page);
}
emul_write:
#endif
return emulator_write_emulated(addr, new, bytes, vcpu);
}