Commit 4c26b4cd authored Apr 02, 2009 by Sheng Yang Committed by Avi Kivity Jun 10, 2009

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



1. It's related to a Linux kernel bug which fixed by Ingo on
07a66d7c. 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>
Signed-off-by: Avi Kivity <avi@redhat.com>

parent 64a7ec06

arch/x86/kvm/mmu.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -2208,13 +2208,14 @@ 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;
		}

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