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>
diff --git a/drivers/kvm/x86.c b/drivers/kvm/x86.c
index 9db4e32..3b79684 100644
--- a/drivers/kvm/x86.c
+++ b/drivers/kvm/x86.c
@@ -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 @@
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);
}