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KVM: arm64: PMU: Set raw values from user to PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR}

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Commit a45f41d754 ("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: a45f41d754 ("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>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250315-pmc-v5-1-ecee87dab216@daynix.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Akihiko Odaki
2025-03-15 18:12:10 +09:00
committed by Oliver Upton
parent 7eb172143d
commit f2aeb7bbd5
1 changed files with 2 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
arch/arm64/kvm/sys_regs.c
View File

@@ -1051,26 +1051,9 @@ 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_accessible_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;
u64 mask = kvm_pmu_accessible_counter_mask(vcpu);
__vcpu_sys_reg(vcpu, r->reg) = val & mask;
return 0;
}