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From: Sheng Yang <sheng@linux.intel.com>
To: Avi Kivity <avi@redhat.com>
Cc: Eddie Dong <eddie.dong@intel.com>,
	kvm@vger.kernel.org, Sheng Yang <sheng@linux.intel.com>
Subject: [PATCH] KVM: Discard reserved bits checking on PDE bit 7-8
Date: Thu,  2 Apr 2009 10:28:37 +0800	[thread overview]
Message-ID: <1238639317-23994-1-git-send-email-sheng@linux.intel.com> (raw)

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(-)

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;
 	}
-- 
1.5.4.5


             reply	other threads:[~2009-04-02  2:28 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-02  2:28 Sheng Yang [this message]
2009-04-02  8:58 ` [PATCH] KVM: Discard reserved bits checking on PDE bit 7-8 Avi Kivity

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