From 1db4aaa05589454c674b1c117263997dcac515f3 Mon Sep 17 00:00:00 2001 From: Akihiko Odaki Date: Sat, 15 Mar 2025 18:12:13 +0900 Subject: [PATCH] KVM: arm64: PMU: Reload when user modifies registers Commit d0c94c49792c ("KVM: arm64: Restore PMU configuration on first run") added the code to reload the PMU configuration on first run. It is also important to keep the correct state even if system registers are modified after first run, specifically when debugging Windows on QEMU with GDB; QEMU tries to write back all visible registers when resuming the VM execution with GDB, corrupting the PMU state. Windows always uses the PMU so this can cause adverse effects on that particular OS. The usual register writes and reset are already handled independently, but register writes from userspace are not covered. Trigger the code to reload the PMU configuration for them instead so that PMU configuration changes made by users will be applied also after the first run. Signed-off-by: Akihiko Odaki Reviewed-by: Marc Zyngier Link: https://lore.kernel.org/r/20250315-pmc-v5-4-ecee87dab216@daynix.com Signed-off-by: Oliver Upton --- arch/arm64/kvm/pmu-emul.c | 3 --- arch/arm64/kvm/sys_regs.c | 4 ++++ 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index 593216bc14f0..8e10124a7420 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@ -917,9 +917,6 @@ int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu) return -EINVAL; } - /* One-off reload of the PMU on first run */ - kvm_make_request(KVM_REQ_RELOAD_PMU, vcpu); - return 0; } diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 4d1ef47d0049..727579acc7f6 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1070,6 +1070,8 @@ static int set_pmreg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, u64 va u64 mask = kvm_pmu_accessible_counter_mask(vcpu); __vcpu_sys_reg(vcpu, r->reg) = val & mask; + kvm_make_request(KVM_REQ_RELOAD_PMU, vcpu); + return 0; } @@ -1228,6 +1230,8 @@ static int set_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, val |= ARMV8_PMU_PMCR_LC; __vcpu_sys_reg(vcpu, r->reg) = val; + kvm_make_request(KVM_REQ_RELOAD_PMU, vcpu); + return 0; }