Re: [Xen-devel] [PATCH for-4.11] x86/SVM: Fix intercepted {RD, WR}MSR for the SYS{CALL, ENTER} MSRs

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 04/25/2018 09:49 AM, Jan Beulich wrote:
>>>> On 24.04.18 at 20:51, <andrew.cooper3@xxxxxxxxxx> wrote:
>> --- a/xen/arch/x86/hvm/svm/svm.c
>> +++ b/xen/arch/x86/hvm/svm/svm.c
>> @@ -1883,6 +1883,22 @@ static int svm_msr_read_intercept(unsigned int msr, 
>> uint64_t *msr_content)
>>      switch ( msr )
>>      {
>>      case MSR_IA32_SYSENTER_CS:
>> +    case MSR_IA32_SYSENTER_ESP:
>> +    case MSR_IA32_SYSENTER_EIP:
> 
> These three do not require sync-ing, as their values aren't read from the 
> VMCB.
> (They do require sync-ing on the write path).
> 
> I also don't think this is going to fully resolve Razvan's issue (not the 
> least
> because the code paths you adjust aren't involved in his scenario): As
> pointed out in a private mail, I think vmcb_in_sync needs to start out as
> true for a vCPU, and may need setting to true upon context set and/or
> reset/init emulation.

Doing arch_svm->vmcb_in_sync = 1; in construct_vmcb() does solve the
issue. I can't unfortunately test if it also needs setting in other
places as our internal patches still need some work so introspection is
not yet fully functional on SVM (mem_access events specifically are a
bit of a problem).


Thanks,
Razvan

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