On Mon, Dec 10, 2007 at 11:30:11PM +0200, Avi Kivity wrote:
> Marcelo Tosatti wrote:
> >Emulate cmpxchg8b atomically on i386. This is required to avoid a guest
> >pte walker from seeing a splitted write.
> >
> >Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]>
> >
> >diff --git a/drivers/kvm/x86.c b/drivers/kvm/x86.c
> >index 9db4e32..d58d795 100644
> >--- a/drivers/kvm/x86.c
> >+++ b/drivers/kvm/x86.c
> >@@ -1674,6 +1674,33 @@ static int emulator_cmpxchg_emulated(uns
> > 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;
> >+
> >+ val = (u64 *)new;
> >+ page = gfn_to_page(page, gpa >> PAGE_SHIFT);
> >+ addr = kmap_atomic(page, KM_USER0);
> >+ addr += offset_in_page(gpa);
> >+
> >+ set_64bit((unsigned long long *)addr, val);
> >+
> >+ kunmap_atomic(page, KM_USER0);
> >+ kvm_release_page_dirty(page);
> >+
> >+ return X86EMUL_CONTINUE;
> >+ }
> >+#endif
> >+
> >+emul_write:
> > return emulator_write_emulated(addr, new, bytes, vcpu);
> > }
> >
>
> Won't the compiler complain when it sees an unreferenced label?
>
> Also, we should handle the page boundary crossing case (probably by just
> emulating as a write and crosssing fingers).
Pagetable writes should not cross page boundaries, so that should be fine.
------------------
Emulate cmpxchg8b atomically on i386. This is required to avoid a guest
pte walker from seeing a splitted write.
Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]>
diff --git a/drivers/kvm/x86.c b/drivers/kvm/x86.c
index 9db4e32..e37c19d 100644
--- a/drivers/kvm/x86.c
+++ b/drivers/kvm/x86.c
@@ -1674,6 +1674,33 @@ static int emulator_cmpxchg_emulated(uns
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 (((addr + bytes - 1) & PAGE_MASK) != (addr & PAGE_MASK))
+ goto emul_write;
+
+ val = (u64 *)new;
+ page = gfn_to_page(page, gpa >> PAGE_SHIFT);
+ addr = kmap_atomic(page, KM_USER0);
+ addr += offset_in_page(gpa);
+
+ set_64bit((unsigned long long *)addr, val);
+ kunmap_atomic(page, KM_USER0);
+ kvm_release_page_dirty(page);
+ }
+emul_write:
+#endif
+
return emulator_write_emulated(addr, new, bytes, vcpu);
}
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