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x86:

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* zero all padding for KVM_GET_DEBUGREGS
 
 * fix rST warning
 
 * disable vPMU support on hybrid CPUs
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm/x86 fixes from Paolo Bonzini:

 - zero all padding for KVM_GET_DEBUGREGS

 - fix rST warning

 - disable vPMU support on hybrid CPUs

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  kvm: initialize all of the kvm_debugregs structure before sending it to userspace
  perf/x86: Refuse to export capabilities for hybrid PMUs
  KVM: x86/pmu: Disable vPMU support on hybrid CPUs (host PMUs)
  Documentation/hw-vuln: Fix rST warning
This commit is contained in:
Linus Torvalds 2023-02-18 11:07:32 -08:00
commit 5e725d112e
4 changed files with 28 additions and 16 deletions
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3
Documentation/admin-guide/hw-vuln/cross-thread-rsb.rst
View file

@ -88,5 +88,4 @@ capability to override those interceptions, but since this is not common, the
mitigation that covers this path is not enabled by default.
The mitigation for the KVM_CAP_X86_DISABLE_EXITS capability can be turned on
using the boolean module parameter mitigate_smt_rsb, e.g.:
kvm.mitigate_smt_rsb=1
using the boolean module parameter mitigate_smt_rsb, e.g. ``kvm.mitigate_smt_rsb=1``.

12
arch/x86/events/core.c
View file

@ -2974,17 +2974,19 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
{
if (!x86_pmu_initialized()) {
/* This API doesn't currently support enumerating hybrid PMUs. */
if (WARN_ON_ONCE(cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) ||
!x86_pmu_initialized()) {
memset(cap, 0, sizeof(*cap));
return;
}
cap->version = x86_pmu.version;
/*
* KVM doesn't support the hybrid PMU yet.
* Return the common value in global x86_pmu,
* which available for all cores.
* Note, hybrid CPU models get tracked as having hybrid PMUs even when
* all E-cores are disabled via BIOS. When E-cores are disabled, the
* base PMU holds the correct number of counters for P-cores.
*/
cap->version = x86_pmu.version;
cap->num_counters_gp = x86_pmu.num_counters;
cap->num_counters_fixed = x86_pmu.num_counters_fixed;
cap->bit_width_gp = x86_pmu.cntval_bits;

26
arch/x86/kvm/pmu.h
View file

@ -165,15 +165,27 @@ static inline void kvm_init_pmu_capability(void)
{
bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL;
perf_get_x86_pmu_capability(&kvm_pmu_cap);
/*
* For Intel, only support guest architectural pmu
* on a host with architectural pmu.
*/
if ((is_intel && !kvm_pmu_cap.version) || !kvm_pmu_cap.num_counters_gp)
/*
* 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))
enable_pmu = false;
if (enable_pmu) {
perf_get_x86_pmu_capability(&kvm_pmu_cap);
/*
* For Intel, only support guest architectural pmu
* on a host with architectural pmu.
*/
if ((is_intel && !kvm_pmu_cap.version) ||
!kvm_pmu_cap.num_counters_gp)
enable_pmu = false;
}
if (!enable_pmu) {
memset(&kvm_pmu_cap, 0, sizeof(kvm_pmu_cap));
return;

3
arch/x86/kvm/x86.c
View file

@ -5263,12 +5263,11 @@ static void kvm_vcpu_ioctl_x86_get_debugregs(struct kvm_vcpu *vcpu,
{
unsigned long val;
memset(dbgregs, 0, sizeof(*dbgregs));
memcpy(dbgregs->db, vcpu->arch.db, sizeof(vcpu->arch.db));
kvm_get_dr(vcpu, 6, &val);
dbgregs->dr6 = val;
dbgregs->dr7 = vcpu->arch.dr7;
dbgregs->flags = 0;
memset(&dbgregs->reserved, 0, sizeof(dbgregs->reserved));
}
static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,