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Commit 2bacc55c authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Avi Kivity
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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: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 62b9abaa

drivers/kvm/x86.c

+26 −0
Original line number Diff line number Diff line
@@ -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);

}