From 034417c1439a533a315562a57bd340d963eaac6b Mon Sep 17 00:00:00 2001 From: Dapeng Mi Date: Fri, 10 Oct 2025 08:52:39 +0800 Subject: KVM: x86/pmu: Don't try to get perf capabilities for hybrid CPUs Explicitly zero kvm_host_pmu instead of attempting to get the perf PMU capabilities when running on a hybrid CPU to avoid running afoul of perf's sanity check. ------------[ cut here ]------------ WARNING: arch/x86/events/core.c:3089 at perf_get_x86_pmu_capability+0xd/0xc0, Call Trace: kvm_x86_vendor_init+0x1b0/0x1a40 [kvm] vmx_init+0xdb/0x260 [kvm_intel] vt_init+0x12/0x9d0 [kvm_intel] do_one_initcall+0x60/0x3f0 do_init_module+0x97/0x2b0 load_module+0x2d08/0x2e30 init_module_from_file+0x96/0xe0 idempotent_init_module+0x117/0x330 __x64_sys_finit_module+0x73/0xe0 Always read the capabilities for non-hybrid CPUs, i.e. don't entirely revert to reading capabilities if and only if KVM wants to use a PMU, as it may be useful to have the host PMU capabilities available, e.g. if only or debug. Reported-by: Chaitanya Kumar Borah Closes: https://lore.kernel.org/all/70b64347-2aca-4511-af78-a767d5fa8226@intel.com/ Fixes: 51f34b1e650f ("KVM: x86/pmu: Snapshot host (i.e. perf's) reported PMU capabilities") Suggested-by: Sean Christopherson Signed-off-by: Dapeng Mi Link: https://lore.kernel.org/r/20251010005239.146953-1-dapeng1.mi@linux.intel.com [sean: rework changelog, call out hybrid CPUs in shortlog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/pmu.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 40ac4cb44ed2..487ad19a236e 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -108,16 +108,18 @@ void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops) bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL; int min_nr_gp_ctrs = pmu_ops->MIN_NR_GP_COUNTERS; - perf_get_x86_pmu_capability(&kvm_host_pmu); - /* * Hybrid PMUs don't play nice with virtualization without careful * configuration by userspace, and KVM's APIs for reporting supported * vPMU features do not account for hybrid PMUs. Disable vPMU support * for hybrid PMUs until KVM gains a way to let userspace opt-in. */ - if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) + if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) { enable_pmu = false; + memset(&kvm_host_pmu, 0, sizeof(kvm_host_pmu)); + } else { + perf_get_x86_pmu_capability(&kvm_host_pmu); + } if (enable_pmu) { /* -- cgit v1.2.3 From 44c6cb9fe9888b371e31165b2854bd0f4e2787d4 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 3 Oct 2025 16:25:58 -0700 Subject: KVM: guest_memfd: Allow mmap() on guest_memfd for x86 VMs with private memory Allow mmap() on guest_memfd instances for x86 VMs with private memory as the need to track private vs. shared state in the guest_memfd instance is only pertinent to INIT_SHARED. Doing mmap() on private memory isn't terrible useful (yet!), but it's now possible, and will be desirable when guest_memfd gains support for other VMA-based syscalls, e.g. mbind() to set NUMA policy. Lift the restriction now, before MMAP support is officially released, so that KVM doesn't need to add another capability to enumerate support for mmap() on private memory. Fixes: 3d3a04fad25a ("KVM: Allow and advertise support for host mmap() on guest_memfd files") Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: David Hildenbrand Link: https://lore.kernel.org/r/20251003232606.4070510-6-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 4b8138bd4857..fe3dc3eb4331 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -13942,10 +13942,11 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) #ifdef CONFIG_KVM_GUEST_MEMFD /* - * KVM doesn't yet support mmap() on guest_memfd for VMs with private memory - * (the private vs. shared tracking needs to be moved into guest_memfd). + * KVM doesn't yet support initializing guest_memfd memory as shared for VMs + * with private memory (the private vs. shared tracking needs to be moved into + * guest_memfd). */ -bool kvm_arch_supports_gmem_mmap(struct kvm *kvm) +bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm) { return !kvm_arch_has_private_mem(kvm); } -- cgit v1.2.3