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V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo Pieralisi , Steven Price Subject: [PATCH v15 32/37] KVM: arm64: CCA: Set breakpoint parameters through SET_ONE_REG Date: Wed, 15 Jul 2026 15:28:34 +0100 Message-ID: <20260715142841.80544-33-steven.price@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260715142841.80544-1-steven.price@arm.com> References: <20260715142841.80544-1-steven.price@arm.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jean-Philippe Brucker Allow userspace to configure the number of breakpoints and watchpoints of a Realm VM through KVM_SET_ONE_REG ID_AA64DFR0_EL1. The KVM sys_reg handler checks the user value against the maximum value given by RMM (arm64_check_features() gets it from the read_sanitised_id_aa64dfr0_el1() reset handler). Userspace discovers that it can write these fields by issuing a KVM_ARM_GET_REG_WRITABLE_MASKS ioctl. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Steven Price Reviewed-by: Gavin Shan Reviewed-by: Suzuki K Poulose --- arch/arm64/kvm/guest.c | 7 +++++++ arch/arm64/kvm/rmi.c | 3 +++ arch/arm64/kvm/sys_regs.c | 17 +++++++++++------ 3 files changed, 21 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index 5469c9a97fad..3ed563e85572 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -735,6 +735,8 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) return kvm_arm_sys_reg_get_reg(vcpu, reg); } +#define KVM_REG_ARM_ID_AA64DFR0_EL1 ARM64_SYS_REG(3, 0, 0, 5, 0) + /* * The RMI ABI only enables setting some GPRs and PC. The selection of GPRs * that are available depends on the Realm state and the reason for the last @@ -749,6 +751,11 @@ static bool validate_realm_set_reg(struct kvm_vcpu *vcpu, u64 off = core_reg_offset_from_id(reg->id); return kvm_realm_validate_core_reg(off); + } else { + switch (reg->id) { + case KVM_REG_ARM_ID_AA64DFR0_EL1: + return true; + } } return false; diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c index 491097a57328..6850338e2f19 100644 --- a/arch/arm64/kvm/rmi.c +++ b/arch/arm64/kvm/rmi.c @@ -493,6 +493,7 @@ static int realm_create_rd(struct kvm *kvm) void *rd = NULL; phys_addr_t rd_phys, params_phys, top_delegated; size_t pgd_size = kvm_pgtable_stage2_pgd_size(kvm->arch.mmu.vtcr); + u64 dfr0 = kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1); int r; realm->ia_bits = VTCR_EL2_IPA(kvm->arch.mmu.vtcr); @@ -520,6 +521,8 @@ static int realm_create_rd(struct kvm *kvm) params->rtt_level_start = get_start_level(realm); params->rtt_num_start = pgd_size / PAGE_SIZE; params->rtt_base = kvm->arch.mmu.pgd_phys; + params->num_bps = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0); + params->num_wps = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0); params->hash_algo = RMI_HASH_SHA_256; if (kvm->arch.arm_pmu) { diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index e0fe9f2562bc..e47be8f8d259 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2174,6 +2174,9 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu, { u8 debugver = SYS_FIELD_GET(ID_AA64DFR0_EL1, DebugVer, val); u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, val); + u8 bps = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, val); + u8 wps = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, val); + u8 ctx_cmps = SYS_FIELD_GET(ID_AA64DFR0_EL1, CTX_CMPs, val); /* * Prior to commit 3d0dba5764b9 ("KVM: arm64: PMU: Move the @@ -2193,10 +2196,11 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu, val &= ~ID_AA64DFR0_EL1_PMUVer_MASK; /* - * ID_AA64DFR0_EL1.DebugVer is one of those awkward fields with a - * nonzero minimum safe value. + * ID_AA64DFR0_EL1.DebugVer, BRPs and WRPs all have to be greater than + * zero. CTX_CMPs is never greater than BRPs. */ - if (debugver < ID_AA64DFR0_EL1_DebugVer_IMP) + if (debugver < ID_AA64DFR0_EL1_DebugVer_IMP || !bps || !wps || + ctx_cmps > bps) return -EINVAL; if (ignore_feat_doublelock(vcpu, val)) { @@ -2429,10 +2433,11 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, mutex_lock(&vcpu->kvm->arch.config_lock); /* - * Once the VM has started the ID registers are immutable. Reject any - * write that does not match the final register value. + * Once the VM has started or the Realm descriptor is created, the ID + * registers are immutable. Reject any write that does not match the + * final register value. */ - if (kvm_vm_has_ran_once(vcpu->kvm)) { + if (kvm_vm_has_ran_once(vcpu->kvm) || kvm_realm_is_created(vcpu->kvm)) { if (val != read_id_reg(vcpu, rd)) ret = -EBUSY; else -- 2.43.0