Proxmox-Port/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2025-08-17 18:55:22 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

KVM: arm64: Allow userspace to limit the number of PMU counters for EL2 VMs

Browse Source 
As long as we had purely EL1 VMs, we could easily update the number
of guest-visible counters by letting userspace write to PMCR_EL0.N.

With VMs started at EL2, PMCR_EL1.N only reflects MDCR_EL2.HPMN,
and we don't have a good way to limit it.

For this purpose, introduce a new PMUv3 attribute that allows
limiting the maximum number of counters. This requires the explicit
selection of a PMU.

Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2025-04-09 11:53:15 +01:00
parent 0224353343
commit b7628c7973
3 changed files with 53 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
Documentation/virt/kvm/devices/vcpu.rst
View File

@ -137,6 +137,30 @@ exit_reason = KVM_EXIT_FAIL_ENTRY and populate the fail_entry struct by setting
hardare_entry_failure_reason field to KVM_EXIT_FAIL_ENTRY_CPU_UNSUPPORTED and
the cpu field to the processor id.
1.5 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS
--------------------------------------------------
:Parameters: in kvm_device_attr.addr the address to an unsigned int
representing the maximum value taken by PMCR_EL0.N
:Returns:
======= ====================================================
-EBUSY PMUv3 already initialized, a VCPU has already run or
an event filter has already been set
-EFAULT Error accessing the value pointed to by addr
-ENODEV PMUv3 not supported or GIC not initialized
-EINVAL No PMUv3 explicitly selected, or value of N out of
range
======= ====================================================
Set the number of implemented event counters in the virtual PMU. This
mandates that a PMU has explicitly been selected via
KVM_ARM_VCPU_PMU_V3_SET_PMU, and will fail when no PMU has been
explicitly selected, or the number of counters is out of range for the
selected PMU. Selecting a new PMU cancels the effect of setting this
attribute.
2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
=================================

1
arch/arm64/include/uapi/asm/kvm.h
View File

@ -435,6 +435,7 @@ enum {
#define KVM_ARM_VCPU_PMU_V3_INIT 1
#define KVM_ARM_VCPU_PMU_V3_FILTER 2
#define KVM_ARM_VCPU_PMU_V3_SET_PMU 3
#define KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS 4
#define KVM_ARM_VCPU_TIMER_CTRL 1
#define KVM_ARM_VCPU_TIMER_IRQ_VTIMER 0
#define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1

24
arch/arm64/kvm/pmu-emul.c
View File

@ -1104,6 +1104,20 @@ static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
return ret;
}
static int kvm_arm_pmu_v3_set_nr_counters(struct kvm_vcpu *vcpu, unsigned int n)
{
struct kvm *kvm = vcpu->kvm;
if (!kvm->arch.arm_pmu)
return -EINVAL;
if (n > kvm_arm_pmu_get_max_counters(kvm))
return -EINVAL;
kvm_arm_set_nr_counters(kvm, n);
return 0;
}
int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
struct kvm *kvm = vcpu->kvm;
@ -1200,6 +1214,15 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
return kvm_arm_pmu_v3_set_pmu(vcpu, pmu_id);
}
case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS: {
unsigned int __user *uaddr = (unsigned int __user *)(long)attr->addr;
unsigned int n;
if (get_user(n, uaddr))
return -EFAULT;
return kvm_arm_pmu_v3_set_nr_counters(vcpu, n);
}
case KVM_ARM_VCPU_PMU_V3_INIT:
return kvm_arm_pmu_v3_init(vcpu);
}
@ -1238,6 +1261,7 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
case KVM_ARM_VCPU_PMU_V3_INIT:
case KVM_ARM_VCPU_PMU_V3_FILTER:
case KVM_ARM_VCPU_PMU_V3_SET_PMU:
case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS:
if (kvm_vcpu_has_pmu(vcpu))
return 0;
}