Commit 42773357 authored by Reiji Watanabe's avatar Reiji Watanabe Committed by Oliver Upton
Browse files

KVM: arm64: Select default PMU in KVM_ARM_VCPU_INIT handler 



Future changes to KVM's sysreg emulation will rely on having a valid PMU
instance to determine the number of implemented counters (PMCR_EL0.N).
This is earlier than when userspace is expected to modify the vPMU
device attributes, where the default is selected today.

Select the default PMU when handling KVM_ARM_VCPU_INIT such that it is
available in time for sysreg emulation.

Reviewed-by: default avatarSebastian Ott <sebott@redhat.com>
Co-developed-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarReiji Watanabe <reijiw@google.com>
Signed-off-by: default avatarRaghavendra Rao Ananta <rananta@google.com>
Link: https://lore.kernel.org/r/20231020214053.2144305-3-rananta@google.com


[Oliver: rewrite changelog]
Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 1616ca6f

arch/arm64/kvm/arm.c

+19 −0
Original line number Diff line number Diff line
@@ -1229,6 +1229,21 @@ static bool kvm_vcpu_init_changed(struct kvm_vcpu *vcpu, 
	return !bitmap_equal(vcpu->arch.features, &features, KVM_VCPU_MAX_FEATURES);

}



static int kvm_setup_vcpu(struct kvm_vcpu *vcpu)

{

	struct kvm *kvm = vcpu->kvm;

	int ret = 0;



	/*

	 * When the vCPU has a PMU, but no PMU is set for the guest

	 * yet, set the default one.

	 */

	if (kvm_vcpu_has_pmu(vcpu) && !kvm->arch.arm_pmu)

		ret = kvm_arm_set_default_pmu(kvm);



	return ret;

}



static int __kvm_vcpu_set_target(struct kvm_vcpu *vcpu,

				 const struct kvm_vcpu_init *init)

{
@@ -1244,6 +1259,10 @@ static int __kvm_vcpu_set_target(struct kvm_vcpu *vcpu, 


	bitmap_copy(vcpu->arch.features, &features, KVM_VCPU_MAX_FEATURES);



	ret = kvm_setup_vcpu(vcpu);

	if (ret)

		goto out_unlock;



	/* Now we know what it is, we can reset it. */

	ret = kvm_reset_vcpu(vcpu);

	if (ret) {

arch/arm64/kvm/pmu-emul.c

+4 −12
Original line number Diff line number Diff line
@@ -717,10 +717,9 @@ static struct arm_pmu *kvm_pmu_probe_armpmu(void) 
	 * It is still necessary to get a valid cpu, though, to probe for the

	 * default PMU instance as userspace is not required to specify a PMU

	 * type. In order to uphold the preexisting behavior KVM selects the

	 * PMU instance for the core where the first call to the

	 * KVM_ARM_VCPU_PMU_V3_CTRL attribute group occurs. A dependent use case

	 * would be a user with disdain of all things big.LITTLE that affines

	 * the VMM to a particular cluster of cores.

	 * PMU instance for the core during vcpu init. A dependent use

	 * case would be a user with disdain of all things big.LITTLE that

	 * affines the VMM to a particular cluster of cores.

	 *

	 * In any case, userspace should just do the sane thing and use the UAPI

	 * to select a PMU type directly. But, be wary of the baggage being
@@ -893,7 +892,7 @@ static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu) 
 * where vCPUs can be scheduled on any core but the guest

 * counters could stop working.

 */

static int kvm_arm_set_default_pmu(struct kvm *kvm)

int kvm_arm_set_default_pmu(struct kvm *kvm)

{

	struct arm_pmu *arm_pmu = kvm_pmu_probe_armpmu();
@@ -946,13 +945,6 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) 
	if (vcpu->arch.pmu.created)

		return -EBUSY;



	if (!kvm->arch.arm_pmu) {

		int ret = kvm_arm_set_default_pmu(kvm);



		if (ret)

			return ret;

	}



	switch (attr->attr) {

	case KVM_ARM_VCPU_PMU_V3_IRQ: {

		int __user *uaddr = (int __user *)(long)attr->addr;

include/kvm/arm_pmu.h

+6 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ void kvm_vcpu_pmu_resync_el0(void); 
})



u8 kvm_arm_pmu_get_pmuver_limit(void);

int kvm_arm_set_default_pmu(struct kvm *kvm);



#else

struct kvm_pmu {
@@ -174,6 +175,11 @@ static inline u8 kvm_arm_pmu_get_pmuver_limit(void) 
}

static inline void kvm_vcpu_pmu_resync_el0(void) {}



static inline int kvm_arm_set_default_pmu(struct kvm *kvm)

{

	return -ENODEV;

}



#endif



#endif