diff mbox

[1/1] KVM: MMU: Fix 64-bit paging breakage on x86_32

Message ID 20110428070836.4099477c.takuya.yoshikawa@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Takuya Yoshikawa April 27, 2011, 10:08 p.m. UTC 
From: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>

Fix regression introduced by
  commit e30d2a170506830d5eef5e9d7990c5aedf1b0a51
  KVM: MMU: Optimize guest page table walk

On x86_32, get_user() does not support 64-bit values and we fail to
build KVM at the point of 64-bit paging.

This patch fixes this by using get_user() twice for that condition.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Reported-by: Jan Kiszka <jan.kiszka@web.de>
---
 arch/x86/kvm/paging_tmpl.h |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

Comments

Avi Kivity April 28, 2011, 10:06 a.m. UTC | #1 
On 04/28/2011 01:08 AM, Takuya Yoshikawa wrote:
> From: Takuya Yoshikawa<yoshikawa.takuya@oss.ntt.co.jp>
>
> Fix regression introduced by
>    commit e30d2a170506830d5eef5e9d7990c5aedf1b0a51
>    KVM: MMU: Optimize guest page table walk
>
> On x86_32, get_user() does not support 64-bit values and we fail to
> build KVM at the point of 64-bit paging.
>
> This patch fixes this by using get_user() twice for that condition.
>

Applied, thanks.
diff mbox

Patch

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 652d56c..7d36ac9 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 (unlikely(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 (unlikely(get_user(pte, ptep_user))) {
+		if (unlikely(FNAME(read_gpte)(&pte, ptep_user))) {
 			present = false;
 			break;
 		}