Re: [PATCH] KVM: VMX: Fix 32bit Windows blue screen with EPT

[Avi Kivity <avi@redhat.com>]

On 12/30/2010 10:35 AM, Sheng Yang wrote:
> After CR0 is changed during VMExit, the result of kvm_read_cr3() may be
> different. Commit d95bfcdd7cda4dfdac9588e684bc7c75794a075e "KVM: Fetch guest
> cr3 from hardware on demand" caused 32bit Windows guest blue screen when using
> with EPT. This patch fixes it by decache CR3 before CR0 change, for both
> paging to nonpaging, and nonpaging to paging switch.
>
> Signed-off-by: Sheng Yang<sheng@linux.intel.com>
> ---
>
> But I haven't found the exactly point affected by this, any clue?
>

Can't see it either.

> @@ -1921,8 +1921,7 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
>   					unsigned long cr0,
>   					struct kvm_vcpu *vcpu)
>   {
> -	ulong cr3;
> -
> +	kvm_read_cr3(vcpu);

Without this line, it fails?

I think it's better to call vmx_decache_cr3() explicitly, since it 
explains what we're doing.  vmx_decache_cr3 depends on arch.cr0, and 
we're changing that here.

>   	if (!(cr0&  X86_CR0_PG)) {
>   		/* From paging/starting to nonpaging */
>   		vmcs_write32(CPU_BASED_VM_EXEC_CONTROL,
> @@ -1937,11 +1936,8 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
>   			     vmcs_read32(CPU_BASED_VM_EXEC_CONTROL)&
>   			~(CPU_BASED_CR3_LOAD_EXITING |
>   			       CPU_BASED_CR3_STORE_EXITING));
> -		/* Must fetch cr3 before updating cr0 */
> -		cr3 = kvm_read_cr3(vcpu);
>   		vcpu->arch.cr0 = cr0;
>   		vmx_set_cr4(vcpu, kvm_read_cr4(vcpu));
> -		vmx_set_cr3(vcpu, cr3);

This is indeed bogus.  But what ensures that we'll have the correct 
GUEST_CR3 after enabling paging?

>   	}
>
>   	if (!(cr0&  X86_CR0_WP))


-- 
error compiling committee.c: too many arguments to function