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[2003:f6:af0e:4d00:dda5:3016:e366:575f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4391da96502sm153559395e9.1.2025.02.10.07.49.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2025 07:49:55 -0800 (PST) From: Sebastian Ott To: Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Shameer Kolothum Cc: Cornelia Huck , Eric Auger , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH 1/4] KVM: arm64: Allow userspace to change MIDR_EL1 Date: Mon, 10 Feb 2025 16:49:50 +0100 Message-ID: <20250210154953.27002-2-sebott@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250210154953.27002-1-sebott@redhat.com> References: <20250210154953.27002-1-sebott@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Enable VMMs to write MIDR_EL1 by treating it as a VM ID register. Since MIDR_EL1 is not handled as a proper arm64_ftr_reg apply only a sanity check against the writable mask to ensure the reserved bits are 0. Signed-off-by: Sebastian Ott --- arch/arm64/include/asm/kvm_host.h | 3 +++ arch/arm64/kvm/sys_regs.c | 37 +++++++++++++++++++++++++++---- 2 files changed, 36 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm= _host.h index 7cfa024de4e3..3db8c773339e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -373,6 +373,7 @@ struct kvm_arch { #define KVM_ARM_ID_REG_NUM (IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1) u64 id_regs[KVM_ARM_ID_REG_NUM]; =20 + u64 midr_el1; u64 ctr_el0; =20 /* Masks for VNCR-backed and general EL2 sysregs */ @@ -1469,6 +1470,8 @@ static inline u64 *__vm_id_reg(struct kvm_arch *ka, u= 32 reg) switch (reg) { case sys_reg(3, 0, 0, 1, 0) ... sys_reg(3, 0, 0, 7, 7): return &ka->id_regs[IDREG_IDX(reg)]; + case SYS_MIDR_EL1: + return &ka->midr_el1; case SYS_CTR_EL0: return &ka->ctr_el0; default: diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 82430c1e1dd0..cc94bed7299d 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1666,7 +1666,7 @@ static bool is_feature_id_reg(u32 encoding) */ static inline bool is_vm_ftr_id_reg(u32 id) { - if (id =3D=3D SYS_CTR_EL0) + if (id =3D=3D SYS_CTR_EL0 || id =3D=3D SYS_MIDR_EL1) return true; =20 return (sys_reg_Op0(id) =3D=3D 3 && sys_reg_Op1(id) =3D=3D 0 && @@ -1999,6 +1999,22 @@ static int get_id_reg(struct kvm_vcpu *vcpu, const s= truct sys_reg_desc *rd, return 0; } =20 +static bool skip_feature_check(u32 reg) +{ + return (reg =3D=3D SYS_MIDR_EL1); +} + +/* + * For non ftr regs do a limited test against the writable mask only. + */ +static int arm64_check_mask(const struct sys_reg_desc *rd, u64 val) +{ + if ((rd->val & val) !=3D val) + return -EINVAL; + + return 0; +} + static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, u64 val) { @@ -2021,7 +2037,11 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const s= truct sys_reg_desc *rd, return ret; } =20 - ret =3D arm64_check_features(vcpu, rd, val); + if (skip_feature_check(id)) + ret =3D arm64_check_mask(rd, val); + else + ret =3D arm64_check_features(vcpu, rd, val); + if (!ret) kvm_set_vm_id_reg(vcpu->kvm, id, val); =20 @@ -2493,6 +2513,15 @@ static bool access_mdcr(struct kvm_vcpu *vcpu, return true; } =20 +#define FUNCTION_RESET(reg) \ + static u64 reset_##reg(struct kvm_vcpu *v, \ + const struct sys_reg_desc *r) \ + { \ + return read_sysreg(reg); \ + } + +FUNCTION_RESET(midr_el1) + =20 /* * Architected system registers. @@ -2542,6 +2571,8 @@ static const struct sys_reg_desc sys_reg_descs[] =3D { =20 { SYS_DESC(SYS_DBGVCR32_EL2), undef_access, reset_val, DBGVCR32_EL2, 0 }, =20 + { ID_DESC(MIDR_EL1), .set_user =3D set_id_reg, .visibility =3D id_visibil= ity, + .reset =3D reset_midr_el1, .val =3D (u32)-1 }, { SYS_DESC(SYS_MPIDR_EL1), NULL, reset_mpidr, MPIDR_EL1 }, =20 /* @@ -4594,13 +4625,11 @@ id_to_sys_reg_desc(struct kvm_vcpu *vcpu, u64 id, return ((struct sys_reg_desc *)r)->val; \ } =20 -FUNCTION_INVARIANT(midr_el1) FUNCTION_INVARIANT(revidr_el1) FUNCTION_INVARIANT(aidr_el1) =20 /* ->val is filled in by kvm_sys_reg_table_init() */ static struct sys_reg_desc invariant_sys_regs[] __ro_after_init =3D { - { SYS_DESC(SYS_MIDR_EL1), NULL, reset_midr_el1 }, { SYS_DESC(SYS_REVIDR_EL1), NULL, reset_revidr_el1 }, { SYS_DESC(SYS_AIDR_EL1), NULL, reset_aidr_el1 }, }; --=20 2.42.0