diff mbox

[1/1,v2] KVM: MMU: Optimize guest page table walk

Message ID 20110427012617.36fdc6d7.takuya.yoshikawa@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Takuya Yoshikawa April 26, 2011, 4:26 p.m. UTC 
On Tue, 26 Apr 2011 17:54:24 +0300
Avi Kivity <avi@redhat.com> wrote:

> Please post a simple patch that uses two get_user()s for that case 
> (64-bit pte on 32-bit host).  Then work with the x86 tree to see if 
> they'll accept 64-bit get_user(), and once they do, we can go back to a 
> simple get_user() again.
> 

I made a patch which seems to reflect what you said!
If this kind of fix is OK with you, I'll test on both x86_32 and x86_64,
and send the patch with some changelog tomorrow.

Thanks,
  Takuya

---
 arch/x86/kvm/paging_tmpl.h |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

Comments

Avi Kivity April 26, 2011, 5:16 p.m. UTC | #1 
On 04/26/2011 07:26 PM, Takuya Yoshikawa wrote:
> On Tue, 26 Apr 2011 17:54:24 +0300
> Avi Kivity<avi@redhat.com>  wrote:
>
> >  Please post a simple patch that uses two get_user()s for that case
> >  (64-bit pte on 32-bit host).  Then work with the x86 tree to see if
> >  they'll accept 64-bit get_user(), and once they do, we can go back to a
> >  simple get_user() again.
> >
>
> I made a patch which seems to reflect what you said!
> If this kind of fix is OK with you, I'll test on both x86_32 and x86_64,
> and send the patch with some changelog tomorrow.
>

Yes, that looks right.
diff mbox

Patch

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index a32a1c8..1e44969 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -115,6 +115,20 @@  static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
 	return access;
 }
 
+static int FNAME(read_gpte)(pt_element_t *pte, pt_element_t __user *ptep_user)
+{
+#if defined(CONFIG_X86_32) && (PTTYPE == 64)
+	u32 *p = (u32 *)pte;
+	u32 __user *p_user = (u32 __user *)ptep_user;
+
+	if (get_user(*p, p_user))
+		return -EFAULT;
+	return get_user(*(p + 1), p_user + 1);
+#else
+	return get_user(*pte, ptep_user);
+#endif
+}
+
 /*
  * Fetch a guest pte for a guest virtual address
  */
@@ -185,7 +199,7 @@  walk:
 		}
 
 		ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
-		if (get_user(pte, ptep_user)) {
+		if (FNAME(read_gpte)(&pte, ptep_user)) {
 			present = false;
 			break;
 		}