diff options
| author | Alexandru Elisei <alexandru.elisei@arm.com> | 2025-09-02 14:08:33 +0100 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2025-09-10 02:56:19 -0700 |
| commit | da2e743419cb5f4ee88cd66c4363951b444207cf (patch) | |
| tree | 885eec7a78474f26da94068a706b8bbbe1957bc7 /arch/arm64/kvm/debug.c | |
| parent | efad60e4605721b829a49bcaa6afc517a80a7247 (diff) | |
KVM: arm64: VHE: Save and restore host MDCR_EL2 value correctly
Prior to commit 75a5fbaf6623 ("KVM: arm64: Compute MDCR_EL2 at
vcpu_load()"), host MDCR_EL2 was saved correctly:
kvm_arch_vcpu_load()
kvm_vcpu_load_debug() /* Doesn't touch hardware MDCR_EL2. */
kvm_vcpu_load_vhe()
__activate_traps_common()
/* Saves host MDCR_EL2. */
*host_data_ptr(host_debug_state.mdcr_el2) = read_sysreg(mdcr_el2)
/* Writes VCPU MDCR_EL2. */
write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2)
The MDCR_EL2 value saved previously was restored in
kvm_arch_vcpu_put() -> kvm_vcpu_put_vhe().
After the aforementioned commit, host MDCR_EL2 is never saved:
kvm_arch_vcpu_load()
kvm_vcpu_load_debug() /* Writes VCPU MDCR_EL2 */
kvm_vcpu_load_vhe()
__activate_traps_common()
/* Saves **VCPU** MDCR_EL2. */
*host_data_ptr(host_debug_state.mdcr_el2) = read_sysreg(mdcr_el2)
/* Writes VCPU MDCR_EL2 a second time. */
write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2)
kvm_arch_vcpu_put() -> kvm_vcpu_put_vhe() then restores the VCPU MDCR_EL2
value. Also VCPU's MDCR_EL2 value gets written to hardware twice now.
Fix this by saving the host MDCR_EL2 in kvm_arch_vcpu_load() before it gets
overwritten by the VCPU's MDCR_EL2 value, and restore it on VCPU put.
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250902130833.338216-3-alexandru.elisei@arm.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Diffstat (limited to 'arch/arm64/kvm/debug.c')
| -rw-r--r-- | arch/arm64/kvm/debug.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index fee6e882490a..e027d9c32b0d 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -145,6 +145,9 @@ void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu) /* Must be called before kvm_vcpu_load_vhe() */ KVM_BUG_ON(vcpu_get_flag(vcpu, SYSREGS_ON_CPU), vcpu->kvm); + if (has_vhe()) + *host_data_ptr(host_debug_state.mdcr_el2) = read_sysreg(mdcr_el2); + /* * Determine which of the possible debug states we're in: * @@ -191,6 +194,9 @@ void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu) void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu) { + if (has_vhe()) + write_sysreg(*host_data_ptr(host_debug_state.mdcr_el2), mdcr_el2); + if (likely(!(vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))) return; |