Re: [Xen-devel] [PATCH v3 1/8] x86/vmx_update_guest_cr: minor optimization

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.07.16 at 13:39, <czuzu@xxxxxxxxxxxxxxx> wrote:
> On 7/6/2016 6:49 PM, Corneliu ZUZU wrote:
>> Minor optimization @ vmx_update_guest_cr: checks if 
> v->arch.hvm_vmx.exec_control
>> was modified before actually calling vmx_update_cpu_exec_control(v).
>>
>> Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
>> ---
>> Changed since v2: <nothing>
>> ---
>>   xen/arch/x86/hvm/vmx/vmx.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>> index df19579..8ab074f 100644
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -1434,8 +1434,10 @@ static void vmx_update_guest_cr(struct vcpu *v, 
> unsigned int cr)
>>           if ( paging_mode_hap(v->domain) )
>>           {
>>               /* Manage GUEST_CR3 when CR0.PE=0. */
>> +            uint32_t old_ctls = v->arch.hvm_vmx.exec_control;
>>               uint32_t cr3_ctls = (CPU_BASED_CR3_LOAD_EXITING |
>>                                    CPU_BASED_CR3_STORE_EXITING);
>> +
>>               v->arch.hvm_vmx.exec_control &= ~cr3_ctls;
>>               if ( !hvm_paging_enabled(v) && !vmx_unrestricted_guest(v) )
>>                   v->arch.hvm_vmx.exec_control |= cr3_ctls;
>> @@ -1445,7 +1447,8 @@ static void vmx_update_guest_cr(struct vcpu *v, 
> unsigned int cr)
>>                    monitor_ctrlreg_bitmask(VM_EVENT_X86_CR3) )
>>                   v->arch.hvm_vmx.exec_control |= CPU_BASED_CR3_LOAD_EXITING;
>>   
>> -            vmx_update_cpu_exec_control(v);
>> +            if ( old_ctls != v->arch.hvm_vmx.exec_control )
>> +                vmx_update_cpu_exec_control(v);
>>           }
>>   
>>           if ( !nestedhvm_vcpu_in_guestmode(v) )
> 
> I'm wondering if you could ack this as well (if there's nothing wrong w/ 
> it) and push it to be done with it. :-)

Well, if you had pinged the patch at least once, I probably would.
I don't, however, recall having seen any such ping (only resends).

Jan


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