diff mbox

KVM: Discard reserved bits checking on PDE bit 7-8

Message ID 1238639317-23994-1-git-send-email-sheng@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Sheng Yang April 2, 2009, 2:28 a.m. UTC 
1. It's related to a Linux kernel bug which fixed by Ingo on
07a66d7c53a538e1a9759954a82bb6c07365eff9. The original code exists for quite a
long time, and it would convert a PDE for large page into a normal PDE. But it
fail to fit normal PDE well.  With the code before Ingo's fix, the kernel would
fall reserved bit checking with bit 8 - the remaining global bit of PTE. So the
kernel would receive a double-fault.

2. After discussion, we decide to discard PDE bit 7-8 reserved checking for now.
For this marked as reserved in SDM, but didn't checked by the processor in
fact...

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 arch/x86/kvm/mmu.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

Comments

Avi Kivity April 2, 2009, 8:58 a.m. UTC | #1 
Sheng Yang wrote:
> 1. It's related to a Linux kernel bug which fixed by Ingo on
> 07a66d7c53a538e1a9759954a82bb6c07365eff9. The original code exists for quite a
> long time, and it would convert a PDE for large page into a normal PDE. But it
> fail to fit normal PDE well.  With the code before Ingo's fix, the kernel would
> fall reserved bit checking with bit 8 - the remaining global bit of PTE. So the
> kernel would receive a double-fault.
>
> 2. After discussion, we decide to discard PDE bit 7-8 reserved checking for now.
> For this marked as reserved in SDM, but didn't checked by the processor in
> fact...
>   

Applied, thanks.
diff mbox

Patch

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e0f63b6..a0b130d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2196,7 +2196,7 @@  static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu, int level)
 		break;
 	case PT32E_ROOT_LEVEL:
 		context->rsvd_bits_mask[0][1] = exb_bit_rsvd |
-			rsvd_bits(maxphyaddr, 62);		/* PDE */
+			rsvd_bits(maxphyaddr, 62);	/* PDE */
 		context->rsvd_bits_mask[0][0] = exb_bit_rsvd |
 			rsvd_bits(maxphyaddr, 62); 	/* PTE */
 		context->rsvd_bits_mask[1][1] = exb_bit_rsvd |
@@ -2210,13 +2210,14 @@  static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu, int level)
 		context->rsvd_bits_mask[0][2] = exb_bit_rsvd |
 			rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
 		context->rsvd_bits_mask[0][1] = exb_bit_rsvd |
-			rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
+			rsvd_bits(maxphyaddr, 51);
 		context->rsvd_bits_mask[0][0] = exb_bit_rsvd |
 			rsvd_bits(maxphyaddr, 51);
 		context->rsvd_bits_mask[1][3] = context->rsvd_bits_mask[0][3];
 		context->rsvd_bits_mask[1][2] = context->rsvd_bits_mask[0][2];
 		context->rsvd_bits_mask[1][1] = exb_bit_rsvd |
-			rsvd_bits(maxphyaddr, 51) | rsvd_bits(13, 20);
+			rsvd_bits(maxphyaddr, 51) |
+			rsvd_bits(13, 20);		/* large page */
 		context->rsvd_bits_mask[1][0] = ~0ull;
 		break;
 	}