On 3/22/19 8:04 PM, Vitaly Kuznetsov wrote:
> "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@xxxxxxx> writes:
>
>> Only clear the valid bit when invalidate logical APIC id entry.
>> The current logic clear the valid bit, but also set the rest of
>> the bits (including reserved bits) to 1.
>>
>> Fixes: 98d90582be2e ('svm: Fix AVIC DFR and LDR handling')
>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
>> ---
>> arch/x86/kvm/svm.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 7a4ce1a22ca0..f4fb766e474c 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -4640,7 +4640,7 @@ static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
>> u32 *entry = avic_get_logical_id_entry(vcpu, svm->ldr_reg, flat);
>>
>> if (entry)
>> - WRITE_ONCE(*entry, (u32) ~AVIC_LOGICAL_ID_ENTRY_VALID_MASK);
>> + WRITE_ONCE(*entry, (u32)(*entry & ~AVIC_LOGICAL_ID_ENTRY_VALID_MASK));
>
> I'm not sure how important this is, but this change creates a tiny time
> window between reading from *entry and writing there. Should we use
> atomic bitops instead?
Sure. That is also simpler. I'll send out V2 w/ clear_bit() instead.
Suravee
>
>> }
>>
>> static int avic_handle_ldr_update(struct kvm_vcpu *vcpu)
>
