On Tue, Dec 29, 2020, Like Xu wrote: > Since we know vPMU will not work properly when the guest bit_width(s) of > the [gp|fixed] counters are greater than the host ones, so we can setup a > smaller left shift value and refresh the guest pmu cpuid entry, thus fixing > the following UBSAN shift-out-of-bounds warning: > > shift exponent 197 is too large for 64-bit type 'long long unsigned int' > > Call Trace: > __dump_stack lib/dump_stack.c:79 [inline] > dump_stack+0x107/0x163 lib/dump_stack.c:120 > ubsan_epilogue+0xb/0x5a lib/ubsan.c:148 > __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:395 > intel_pmu_refresh.cold+0x75/0x99 arch/x86/kvm/vmx/pmu_intel.c:348 > kvm_vcpu_after_set_cpuid+0x65a/0xf80 arch/x86/kvm/cpuid.c:177 > kvm_vcpu_ioctl_set_cpuid2+0x160/0x440 arch/x86/kvm/cpuid.c:308 > kvm_arch_vcpu_ioctl+0x11b6/0x2d70 arch/x86/kvm/x86.c:4709 > kvm_vcpu_ioctl+0x7b9/0xdb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3386 > vfs_ioctl fs/ioctl.c:48 [inline] > __do_sys_ioctl fs/ioctl.c:753 [inline] > __se_sys_ioctl fs/ioctl.c:739 [inline] > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Reported-by: syzbot+ae488dc136a4cc6ba32b@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx> > --- > arch/x86/kvm/vmx/pmu_intel.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c > index a886a47daebd..a86a1690e75c 100644 > --- a/arch/x86/kvm/vmx/pmu_intel.c > +++ b/arch/x86/kvm/vmx/pmu_intel.c > @@ -345,6 +345,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) > > pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters, > x86_pmu.num_counters_gp); > + eax.split.bit_width = min_t(int, eax.split.bit_width, x86_pmu.bit_width_gp); > pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1; > pmu->available_event_types = ~entry->ebx & > ((1ull << eax.split.mask_length) - 1); eax.split.mask_length needs similar treatment, doesn't it? > @@ -355,6 +356,8 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) > pmu->nr_arch_fixed_counters = > min_t(int, edx.split.num_counters_fixed, > x86_pmu.num_counters_fixed); > + edx.split.bit_width_fixed = min_t(int, > + edx.split.bit_width_fixed, x86_pmu.bit_width_fixed); > pmu->counter_bitmask[KVM_PMC_FIXED] = > ((u64)1 << edx.split.bit_width_fixed) - 1; > } > -- > 2.29.2 >
