From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Subject: Re: [PATCH] svm/avic: Fix invalidate logical APIC id entry Date: Fri, 22 Mar 2019 14:04:01 +0100 Message-ID: <87ef6zcb7i.fsf@vitty.brq.redhat.com> References: <20190322101706.9377-1-suravee.suthikulpanit@amd.com> Mime-Version: 1.0 Content-Type: text/plain Cc: "joro\@8bytes.org" , "pbonzini\@redhat.com" , "rkrcmar\@redhat.com" , "linux-kernel\@vger.kernel.org" , "kvm\@vger.kernel.org" To: "Suthikulpanit\, Suravee" Return-path: In-Reply-To: <20190322101706.9377-1-suravee.suthikulpanit@amd.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org "Suthikulpanit, Suravee" 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 > --- > 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? > } > > static int avic_handle_ldr_update(struct kvm_vcpu *vcpu) -- Vitaly