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 > > 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@xxxxxxxxxx> > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> > --- > 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 >
