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Wed, 12 Mar 2025 04:56:13 -0700 (PDT) From: Akihiko Odaki Date: Wed, 12 Mar 2025 20:55:55 +0900 Subject: [PATCH v3 1/6] KVM: arm64: PMU: Set raw values from user to PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR} Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250312-pmc-v3-1-0411cab5dc3d@daynix.com> References: <20250312-pmc-v3-0-0411cab5dc3d@daynix.com> In-Reply-To: <20250312-pmc-v3-0-0411cab5dc3d@daynix.com> To: Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Andrew Jones , Shannon Zhao Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, devel@daynix.com, Akihiko Odaki , stable@vger.kernel.org X-Mailer: b4 0.15-dev-edae6 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,CL= R}, PMOVS{SET,CLR}") Signed-off-by: Akihiko Odaki Acked-by: Marc Zyngier --- 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, =20 static int set_pmreg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, = u64 val) { - bool set; - - val &=3D kvm_pmu_valid_counter_mask(vcpu); - - switch (r->reg) { - case PMOVSSET_EL0: - /* CRm[1] being set indicates a SET register, and CLR otherwise */ - set =3D r->CRm & 2; - break; - default: - /* Op2[0] being set indicates a SET register, and CLR otherwise */ - set =3D r->Op2 & 1; - break; - } - - if (set) - __vcpu_sys_reg(vcpu, r->reg) |=3D val; - else - __vcpu_sys_reg(vcpu, r->reg) &=3D ~val; - + __vcpu_sys_reg(vcpu, r->reg) =3D val & kvm_pmu_valid_counter_mask(vcpu); return 0; } =20 --=20 2.48.1