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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: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: a5XV_i5C0fGcxikkUWlEaI7M1qRfhd2AWKPTQpZjdkc_1739202597 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true 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]; + u64 midr_el1; u64 ctr_el0; /* Masks for VNCR-backed and general EL2 sysregs */ @@ -1469,6 +1470,8 @@ static inline u64 *__vm_id_reg(struct kvm_arch *ka, u32 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 == SYS_CTR_EL0) + if (id == SYS_CTR_EL0 || id == SYS_MIDR_EL1) return true; return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 && @@ -1999,6 +1999,22 @@ static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, return 0; } +static bool skip_feature_check(u32 reg) +{ + return (reg == 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) != 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 struct sys_reg_desc *rd, return ret; } - ret = arm64_check_features(vcpu, rd, val); + if (skip_feature_check(id)) + ret = arm64_check_mask(rd, val); + else + ret = arm64_check_features(vcpu, rd, val); + if (!ret) kvm_set_vm_id_reg(vcpu->kvm, id, val); @@ -2493,6 +2513,15 @@ static bool access_mdcr(struct kvm_vcpu *vcpu, return true; } +#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) + /* * Architected system registers. @@ -2542,6 +2571,8 @@ static const struct sys_reg_desc sys_reg_descs[] = { { SYS_DESC(SYS_DBGVCR32_EL2), undef_access, reset_val, DBGVCR32_EL2, 0 }, + { ID_DESC(MIDR_EL1), .set_user = set_id_reg, .visibility = id_visibility, + .reset = reset_midr_el1, .val = (u32)-1 }, { SYS_DESC(SYS_MPIDR_EL1), NULL, reset_mpidr, MPIDR_EL1 }, /* @@ -4594,13 +4625,11 @@ id_to_sys_reg_desc(struct kvm_vcpu *vcpu, u64 id, return ((struct sys_reg_desc *)r)->val; \ } -FUNCTION_INVARIANT(midr_el1) FUNCTION_INVARIANT(revidr_el1) FUNCTION_INVARIANT(aidr_el1) /* ->val is filled in by kvm_sys_reg_table_init() */ static struct sys_reg_desc invariant_sys_regs[] __ro_after_init = { - { 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 }, }; -- 2.42.0