diff options
| author | Alexandru Elisei <alexandru.elisei@arm.com> | 2025-09-02 14:08:32 +0100 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2025-09-10 02:56:19 -0700 |
| commit | efad60e4605721b829a49bcaa6afc517a80a7247 (patch) | |
| tree | 70457300cf1ce6e2e7622c0a4d45efca99f8179d | |
| parent | 860b21c31d16f99b8c37b77993682f7bc8c211d7 (diff) | |
KVM: arm64: Initialize PMSCR_EL1 when in VHE
According to the pseudocode for StatisticalProfilingEnabled() from Arm
DDI0487L.b, PMSCR_EL1 controls profiling at EL1 and EL0:
- PMSCR_EL1.E1SPE controls profiling at EL1.
- PMSCR_EL1.E0SPE controls profiling at EL0 if HCR_EL2.TGE=0.
These two fields reset to UNKNOWN values.
When KVM runs in VHE mode and profiling is enabled in the host, before
entering a guest, KVM does not touch any of the SPE registers, leaving the
buffer enabled, and it clears HCR_EL2.TGE. As a result, depending on the
reset value for the E1SPE and E0SPE fields, KVM might unintentionally
profile a guest. Make the behaviour consistent and predictable by clearing
PMSCR_EL1 when KVM initialises the host debug configuration.
Note that this is not a problem for nVHE, because KVM clears
PMSCR_EL1.{E1SPE,E0SPE} before entering the guest.
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20250902130833.338216-2-alexandru.elisei@arm.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
| -rw-r--r-- | arch/arm64/include/asm/kvm_host.h | 1 | ||||
| -rw-r--r-- | arch/arm64/kvm/arm.c | 4 | ||||
| -rw-r--r-- | arch/arm64/kvm/debug.c | 7 |
3 files changed, 11 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 2b07f0a27a7d..0ee4f6fa3a17 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1369,6 +1369,7 @@ static inline bool kvm_system_needs_idmapped_vectors(void) } void kvm_init_host_debug_data(void); +void kvm_debug_init_vhe(void); void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu); void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu); void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu); diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 5bf101c869c9..bd6b6a620a09 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -2113,8 +2113,10 @@ static void cpu_hyp_init_features(void) { cpu_set_hyp_vector(); - if (is_kernel_in_hyp_mode()) + if (is_kernel_in_hyp_mode()) { kvm_timer_init_vhe(); + kvm_debug_init_vhe(); + } if (vgic_present) kvm_vgic_init_cpu_hardware(); diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index 381382c19fe4..fee6e882490a 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -96,6 +96,13 @@ void kvm_init_host_debug_data(void) } } +void kvm_debug_init_vhe(void) +{ + /* Clear PMSCR_EL1.E{0,1}SPE which reset to UNKNOWN values. */ + if (SYS_FIELD_GET(ID_AA64DFR0_EL1, PMSVer, read_sysreg(id_aa64dfr0_el1))) + write_sysreg_el1(0, SYS_PMSCR); +} + /* * Configures the 'external' MDSCR_EL1 value for the guest, i.e. when the host * has taken over MDSCR_EL1. |