[PATCH] SVM: remove selective CR0 comment

[PATCH] SVM: remove selective CR0 comment

[Joerg Roedel]

There is not selective cr0 intercept bug. The code in the comment sets the
CR0.PG bit. But KVM sets the CR4.PG bit for SVM always to implement the paged
real mode. So the 'mov %eax,%cr0' instruction does not change the CR0.PG bit.
Selective CR0 intercepts only occur when a bit is actually changed. So its the
right behavior that there is no intercept on this instruction.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 arch/x86/kvm/svm.c |   11 -----------
 1 files changed, 0 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 3379e13..55b5076 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -514,17 +514,6 @@ static void init_vmcb(struct vcpu_svm *svm)
 	control->intercept = 	(1ULL << INTERCEPT_INTR) |
 				(1ULL << INTERCEPT_NMI) |
 				(1ULL << INTERCEPT_SMI) |
-		/*
-		 * selective cr0 intercept bug?
-		 *    	0:   0f 22 d8                mov    %eax,%cr3
-		 *	3:   0f 20 c0                mov    %cr0,%eax
-		 *	6:   0d 00 00 00 80          or     $0x80000000,%eax
-		 *	b:   0f 22 c0                mov    %eax,%cr0
-		 * set cr3 ->interception
-		 * get cr0 ->interception
-		 * set cr0 -> no interception
-		 */
-		/*              (1ULL << INTERCEPT_SELECTIVE_CR0) | */
 				(1ULL << INTERCEPT_CPUID) |
 				(1ULL << INTERCEPT_INVD) |
 				(1ULL << INTERCEPT_HLT) |
-- 
1.5.3.7



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Re: [PATCH] SVM: remove selective CR0 comment

[Avi Kivity]

Joerg Roedel wrote:
> There is not selective cr0 intercept bug. The code in the comment sets the
> CR0.PG bit. But KVM sets the CR4.PG bit for SVM always to implement the paged
> real mode. So the 'mov %eax,%cr0' instruction does not change the CR0.PG bit.
> Selective CR0 intercepts only occur when a bit is actually changed. So its the
> right behavior that there is no intercept on this instruction.
>
>   
Applied, thanks.


-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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