Commit a45f41d754e0 ("KVM: arm64: Add {get,set}_user for PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR}") changed KVM_SET_ONE_REG to update the mentioned registers in a way matching with the behavior of guest register writes. This is a breaking change of a UAPI though the new semantics looks cleaner and VMMs are not prepared for this.
Firecracker, QEMU, and crosvm perform migration by listing registers with KVM_GET_REG_LIST, getting their values with KVM_GET_ONE_REG and setting them with KVM_SET_ONE_REG. This algorithm assumes KVM_SET_ONE_REG restores the values retrieved with KVM_GET_ONE_REG without any alteration. However, bit operations added by the earlier commit do not preserve the values retried with KVM_GET_ONE_REG and potentially break migration.
Remove the bit operations that alter the values retrieved with KVM_GET_ONE_REG.
Cc: stable@vger.kernel.org Fixes: a45f41d754e0 ("KVM: arm64: Add {get,set}_user for PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR}") Signed-off-by: Akihiko Odaki akihiko.odaki@daynix.com Acked-by: Marc Zyngier maz@kernel.org --- arch/arm64/kvm/sys_regs.c | 21 +-------------------- 1 file changed, 1 insertion(+), 20 deletions(-)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 42791971f758..0a2ce931a946 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1126,26 +1126,7 @@ static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
static int set_pmreg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, u64 val) { - bool set; - - val &= kvm_pmu_valid_counter_mask(vcpu); - - switch (r->reg) { - case PMOVSSET_EL0: - /* CRm[1] being set indicates a SET register, and CLR otherwise */ - set = r->CRm & 2; - break; - default: - /* Op2[0] being set indicates a SET register, and CLR otherwise */ - set = r->Op2 & 1; - break; - } - - if (set) - __vcpu_sys_reg(vcpu, r->reg) |= val; - else - __vcpu_sys_reg(vcpu, r->reg) &= ~val; - + __vcpu_sys_reg(vcpu, r->reg) = val & kvm_pmu_valid_counter_mask(vcpu); return 0; }