Re: [PATCH 2/5] kvm/svm: enhance MOV CR intercept handler

Andre Przywara
2010-12-07T14:31:37Z

Avi Kivity wrote:
> On 12/07/2010 12:59 PM, Andre Przywara wrote:
>> Newer SVM implementations provide the GPR number in the VMCB, so
>> that the emulation path is no longer necesarry to handle CR
>> register access intercepts. Implement the handling in svm.c and
>> use it when the info is provided.
>>
>> Signed-off-by: Andre Przywara<andre.przywara@amd.com>
>> ---
>> arch/x86/include/asm/svm.h | 2 +
>> arch/x86/kvm/svm.c | 74 +++++++++++++++++++++++++++++++++++++++-----
>> 2 files changed, 68 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
>> index 11dbca7..589fc25 100644
>> --- a/arch/x86/include/asm/svm.h
>> +++ b/arch/x86/include/asm/svm.h
>> ...
>> @@ -2864,14 +2922,14 @@ static int pause_interception(struct vcpu_svm *svm)
>> }
>>
>> static int (*svm_exit_handlers[])(struct vcpu_svm *svm) = {
>> - [SVM_EXIT_READ_CR0] = emulate_on_interception,
>> - [SVM_EXIT_READ_CR3] = emulate_on_interception,
>> - [SVM_EXIT_READ_CR4] = emulate_on_interception,
>> - [SVM_EXIT_READ_CR8] = emulate_on_interception,
>> + [SVM_EXIT_READ_CR0] = cr_interception,
>> + [SVM_EXIT_READ_CR3] = cr_interception,
>> + [SVM_EXIT_READ_CR4] = cr_interception,
>> + [SVM_EXIT_READ_CR8] = cr_interception,
>> [SVM_EXIT_CR0_SEL_WRITE] = emulate_on_interception,
>> [SVM_EXIT_WRITE_CR0] = cr0_write_interception,
>> - [SVM_EXIT_WRITE_CR3] = emulate_on_interception,
>> - [SVM_EXIT_WRITE_CR4] = emulate_on_interception,
>> + [SVM_EXIT_WRITE_CR3] = cr_interception,
>> + [SVM_EXIT_WRITE_CR4] = cr_interception,
>> [SVM_EXIT_WRITE_CR8] = cr8_write_interception,
>
> We could move cr[08]_write_interception into cr_interception, but that
> takes a bit more thought. Best done later.
Yes, I thought about that, too. But since we still have to deal with the
emulation code path, it would not make the code easier. But if we
overwrite the svm_exit_handlers[] on detecting the SVM feature, this
could make more sense. I will check this out.

Thanks for the review, I will address your comments.

Regards,
Andre.