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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id o26sm5489583wmc.17.2021.11.03.07.00.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Nov 2021 07:00:24 -0700 (PDT) From: Vitaly Kuznetsov To: Maxim Levitsky , kvm@vger.kernel.org Cc: Paolo Bonzini , Wanpeng Li , Jim Mattson , Joerg Roedel , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Borislav Petkov , Thomas Gleixner , "H. Peter Anvin" , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Ingo Molnar , Sean Christopherson Subject: Re: [PATCH v2] KVM: x86: inhibit APICv when KVM_GUESTDBG_BLOCKIRQ active In-Reply-To: <8b7949ae8094217c92b714cfd193fc571654cea7.camel@redhat.com> References: <20211103094255.426573-1-mlevitsk@redhat.com> <871r3xnzaw.fsf@vitty.brq.redhat.com> <8b7949ae8094217c92b714cfd193fc571654cea7.camel@redhat.com> Date: Wed, 03 Nov 2021 15:00:23 +0100 Message-ID: <87y265mj9k.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Maxim Levitsky writes: > On Wed, 2021-11-03 at 14:28 +0100, Vitaly Kuznetsov wrote: >> Maxim Levitsky writes: >> >> > KVM_GUESTDBG_BLOCKIRQ relies on interrupts being injected using >> > standard kvm's inject_pending_event, and not via APICv/AVIC. >> > >> > Since this is a debug feature, just inhibit it while it >> > is in use. >> > >> > Fixes: 61e5f69ef0837 ("KVM: x86: implement KVM_GUESTDBG_BLOCKIRQ") >> > >> > Signed-off-by: Maxim Levitsky >> > --- >> > arch/x86/include/asm/kvm_host.h | 1 + >> > arch/x86/kvm/svm/avic.c | 3 ++- >> > arch/x86/kvm/vmx/vmx.c | 3 ++- >> > arch/x86/kvm/x86.c | 3 +++ >> > 4 files changed, 8 insertions(+), 2 deletions(-) >> > >> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> > index 88fce6ab4bbd7..8f6e15b95a4d8 100644 >> > --- a/arch/x86/include/asm/kvm_host.h >> > +++ b/arch/x86/include/asm/kvm_host.h >> > @@ -1034,6 +1034,7 @@ struct kvm_x86_msr_filter { >> > #define APICV_INHIBIT_REASON_IRQWIN 3 >> > #define APICV_INHIBIT_REASON_PIT_REINJ 4 >> > #define APICV_INHIBIT_REASON_X2APIC 5 >> > +#define APICV_INHIBIT_REASON_BLOCKIRQ 6 >> > >> > struct kvm_arch { >> > unsigned long n_used_mmu_pages; >> > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c >> > index 8052d92069e01..affc0ea98d302 100644 >> > --- a/arch/x86/kvm/svm/avic.c >> > +++ b/arch/x86/kvm/svm/avic.c >> > @@ -904,7 +904,8 @@ bool svm_check_apicv_inhibit_reasons(ulong bit) >> > BIT(APICV_INHIBIT_REASON_NESTED) | >> > BIT(APICV_INHIBIT_REASON_IRQWIN) | >> > BIT(APICV_INHIBIT_REASON_PIT_REINJ) | >> > - BIT(APICV_INHIBIT_REASON_X2APIC); >> > + BIT(APICV_INHIBIT_REASON_X2APIC) | >> > + BIT(APICV_INHIBIT_REASON_BLOCKIRQ); >> > >> > return supported & BIT(bit); >> > } >> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> > index 71f54d85f104c..e4fc9ff7cd944 100644 >> > --- a/arch/x86/kvm/vmx/vmx.c >> > +++ b/arch/x86/kvm/vmx/vmx.c >> > @@ -7565,7 +7565,8 @@ static void hardware_unsetup(void) >> > static bool vmx_check_apicv_inhibit_reasons(ulong bit) >> > { >> > ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) | >> > - BIT(APICV_INHIBIT_REASON_HYPERV); >> > + BIT(APICV_INHIBIT_REASON_HYPERV) | >> > + BIT(APICV_INHIBIT_REASON_BLOCKIRQ); >> > >> > return supported & BIT(bit); >> > } >> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> > index ac83d873d65b0..dccf927baa4dd 100644 >> > --- a/arch/x86/kvm/x86.c >> > +++ b/arch/x86/kvm/x86.c >> > @@ -10747,6 +10747,9 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >> > if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) >> > vcpu->arch.singlestep_rip = kvm_get_linear_rip(vcpu); >> > >> > + kvm_request_apicv_update(vcpu->kvm, >> > + !(vcpu->guest_debug & KVM_GUESTDBG_BLOCKIRQ), >> > + APICV_INHIBIT_REASON_BLOCKIRQ); >> > /* >> > * Trigger an rflags update that will inject or remove the trace >> > * flags. >> >> This fixes the problem for me! >> >> Reviewed-by: Vitaly Kuznetsov > > Cool! >> > > Now that I think about it, since guest debug flags are per-vcpu, this code won't > work if there are multiple vCPUs and you enable KVM_GUESTDBG_BLOCKIRQ on all of them > and then disable on this flag on just one of vCPUs, because this code will re-enable APICv/AVIC in this case. > A counter is needed, like you did in synic/autoeoi case. > Right, I completely forgot about this peculiarity! -- Vitaly