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@xxxxxxxxxxxxxxx
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@xxxxxxxxxx>
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
---
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;
}
--
2.48.1
