| Message ID | 20220912214632.14880-1-suravee.suthikulpanit@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: SVM: Fix x2apic logical cluster mode decoding and sanity check | expand |
On Mon, Sep 12, 2022, Suravee Suthikulpanit wrote: > When sending IPI in the X2APIC logical cluster mode, the destination > APIC ID is encoded as: > > * Cluster ID = ICRH[31:16] > * Logical ID = ICRH[15:0] > > Current logic incorrectly decode the ICRH, which causes VM running > with x2AVIC support to fail to boot. Therefore, fix the decoding logic. There are already patches pending[1][2] for the x2AVIC bugs. [1] https://lore.kernel.org/all/20220903002254.2411750-9-seanjc@google.com [2] https://lore.kernel.org/all/20220903002254.2411750-10-seanjc@google.com > > The commit 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast") > also added a check for multiple logical destinations before using > the fast-path. However, the same logic is already existed prior to > the commit. Therefore, remove redundant checking logic. > > Fixes: 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast") > Cc: Maxim Levitsky <mlevitsk@redhat.com> > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> > --- > arch/x86/kvm/svm/avic.c | 19 ++++--------------- > 1 file changed, 4 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c > index 6919dee69f18..45ab49d1f0b8 100644 > --- a/arch/x86/kvm/svm/avic.c > +++ b/arch/x86/kvm/svm/avic.c > @@ -378,8 +378,8 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source > > if (apic_x2apic_mode(source)) { > /* 16 bit dest mask, 16 bit cluster id */ > - bitmap = dest & 0xFFFF0000; > - cluster = (dest >> 16) << 4; > + bitmap = dest & 0xffff; > + cluster = (dest & 0xffff0000) >> 16; > } else if (kvm_lapic_get_reg(source, APIC_DFR) == APIC_DFR_FLAT) { > /* 8 bit dest mask*/ > bitmap = dest; > @@ -387,7 +387,7 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source > } else { > /* 4 bit desk mask, 4 bit cluster id */ > bitmap = dest & 0xF; > - cluster = (dest >> 4) << 2; > + cluster = (dest & 0xf0) >> 4; This is wrong and unrelated. The cluster needs to be shifted back by 2, i.e. multiplied by 4, to leap over each cluster of 4 IDs. > } > > if (unlikely(!bitmap)) > @@ -420,18 +420,7 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source > * For x2APIC logical mode, cannot leverage the index. > * Instead, calculate physical ID from logical ID in ICRH. > */ > - int cluster = (icrh & 0xffff0000) >> 16; > - int apic = ffs(icrh & 0xffff) - 1; > - > - /* > - * If the x2APIC logical ID sub-field (i.e. icrh[15:0]) > - * contains anything but a single bit, we cannot use the > - * fast path, because it is limited to a single vCPU. > - */ > - if (apic < 0 || icrh != (1 << apic)) > - return -EINVAL; > - > - l1_physical_id = (cluster << 4) + apic; > + l1_physical_id = (cluster << 4) + (ffs(bitmap) - 1); > } > } > > -- > 2.34.1 >
On 9/13/2022 12:29 AM, Sean Christopherson wrote: > On Mon, Sep 12, 2022, Suravee Suthikulpanit wrote: >> When sending IPI in the X2APIC logical cluster mode, the destination >> APIC ID is encoded as: >> >> * Cluster ID = ICRH[31:16] >> * Logical ID = ICRH[15:0] >> >> Current logic incorrectly decode the ICRH, which causes VM running >> with x2AVIC support to fail to boot. Therefore, fix the decoding logic. > > There are already patches pending[1][2] for the x2AVIC bugs. > > [1] https://lore.kernel.org/all/20220903002254.2411750-9-seanjc@xxxxxxxxxx > [2] https://lore.kernel.org/all/20220903002254.2411750-10-seanjc@xxxxxxxxxx Ok. Thanks for the pointer. >> >> The commit 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast") >> also added a check for multiple logical destinations before using >> the fast-path. However, the same logic is already existed prior to >> the commit. Therefore, remove redundant checking logic. >> >> Fixes: 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast") >> Cc: Maxim Levitsky <mlevitsk@redhat.com> >> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> >> --- >> arch/x86/kvm/svm/avic.c | 19 ++++--------------- >> 1 file changed, 4 insertions(+), 15 deletions(-) >> >> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c >> index 6919dee69f18..45ab49d1f0b8 100644 >> --- a/arch/x86/kvm/svm/avic.c >> +++ b/arch/x86/kvm/svm/avic.c >> @@ -378,8 +378,8 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source >> >> if (apic_x2apic_mode(source)) { >> /* 16 bit dest mask, 16 bit cluster id */ >> - bitmap = dest & 0xFFFF0000; >> - cluster = (dest >> 16) << 4; >> + bitmap = dest & 0xffff; >> + cluster = (dest & 0xffff0000) >> 16; >> } else if (kvm_lapic_get_reg(source, APIC_DFR) == APIC_DFR_FLAT) { >> /* 8 bit dest mask*/ >> bitmap = dest; >> @@ -387,7 +387,7 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source >> } else { >> /* 4 bit desk mask, 4 bit cluster id */ >> bitmap = dest & 0xF; >> - cluster = (dest >> 4) << 2; >> + cluster = (dest & 0xf0) >> 4; > > This is wrong and unrelated. The cluster needs to be shifted back by 2, i.e. multiplied > by 4, to leap over each cluster of 4 IDs. Ah, I missed the logic that was using the _cluster_ value below. Thanks, Suravee
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 6919dee69f18..45ab49d1f0b8 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -378,8 +378,8 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source if (apic_x2apic_mode(source)) { /* 16 bit dest mask, 16 bit cluster id */ - bitmap = dest & 0xFFFF0000; - cluster = (dest >> 16) << 4; + bitmap = dest & 0xffff; + cluster = (dest & 0xffff0000) >> 16; } else if (kvm_lapic_get_reg(source, APIC_DFR) == APIC_DFR_FLAT) { /* 8 bit dest mask*/ bitmap = dest; @@ -387,7 +387,7 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source } else { /* 4 bit desk mask, 4 bit cluster id */ bitmap = dest & 0xF; - cluster = (dest >> 4) << 2; + cluster = (dest & 0xf0) >> 4; } if (unlikely(!bitmap)) @@ -420,18 +420,7 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source * For x2APIC logical mode, cannot leverage the index. * Instead, calculate physical ID from logical ID in ICRH. */ - int cluster = (icrh & 0xffff0000) >> 16; - int apic = ffs(icrh & 0xffff) - 1; - - /* - * If the x2APIC logical ID sub-field (i.e. icrh[15:0]) - * contains anything but a single bit, we cannot use the - * fast path, because it is limited to a single vCPU. - */ - if (apic < 0 || icrh != (1 << apic)) - return -EINVAL; - - l1_physical_id = (cluster << 4) + apic; + l1_physical_id = (cluster << 4) + (ffs(bitmap) - 1); } }
When sending IPI in the X2APIC logical cluster mode, the destination APIC ID is encoded as: * Cluster ID = ICRH[31:16] * Logical ID = ICRH[15:0] Current logic incorrectly decode the ICRH, which causes VM running with x2AVIC support to fail to boot. Therefore, fix the decoding logic. The commit 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast") also added a check for multiple logical destinations before using the fast-path. However, the same logic is already existed prior to the commit. Therefore, remove redundant checking logic. Fixes: 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast") Cc: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> --- arch/x86/kvm/svm/avic.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-)