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

Avi Kivity
2010-12-07T14:41:44Z

On 12/07/2010 04:30 PM, Andre Przywara wrote:
> 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.
>

In fact the correct thing is to make sure kvm_set_cr0() and
kvm_set_cr8() do the right thing, so that the emulation path invoked
directly (not through a cr intercept) works.

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