From nobody Mon Apr 6 18:29:01 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3FCD8320A0E; Wed, 18 Mar 2026 15:56:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773849415; cv=none; b=K18983q7Yp62EqbGUOqjsc+ElbcSJOQkImfZILojuNNGjVnjvNHci2hCVbfQIWESv2lAM5Vz4gObgRnikrpWcpuf+5qFOhkXH3jJoxtF7nQBa4z64wRszIhBwCjMDHAA543UNv0P6HZRAe5C/EP9sJh6RYBs05XTVoVb4fiHqkU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773849415; c=relaxed/simple; bh=TDIzACepH1NcVihuKXsi1exhnIih6tgh0qLH62fjWwk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CFpFicSM7PoX19NLk+m9g/HFvZBpCCvAa6IpLe7SKCntq0Q6rL+ZKtlGxd49rF1IEgz87kYm7IF37YlarMirc53Bjfq+yFaC6w4cNV/QQ2ssYM/MkQu0xAOYBSP08bG8lftb9v2vN/mDeQLYDyOE/bnFlnzKfCVh6H1YNHYAGcY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7DC88201B; Wed, 18 Mar 2026 08:56:44 -0700 (PDT) Received: from e122027.arm.com (unknown [10.57.61.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4CF413F73B; Wed, 18 Mar 2026 08:56:47 -0700 (PDT) From: Steven Price To: kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Jean-Philippe Brucker , Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , Steven Price Subject: [PATCH v13 40/48] arm64: RMI: Set breakpoint parameters through SET_ONE_REG Date: Wed, 18 Mar 2026 15:54:04 +0000 Message-ID: <20260318155413.793430-41-steven.price@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260318155413.793430-1-steven.price@arm.com> References: <20260318155413.793430-1-steven.price@arm.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" 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 | 2 ++ arch/arm64/kvm/rmi.c | 3 +++ arch/arm64/kvm/sys_regs.c | 17 +++++++++++------ 3 files changed, 16 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index 14302130d341..7cf919db1adc 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -736,6 +736,7 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct= kvm_one_reg *reg) } =20 #define KVM_REG_ARM_PMCR_EL0 ARM64_SYS_REG(3, 3, 9, 12, 0) +#define KVM_REG_ARM_ID_AA64DFR0_EL1 ARM64_SYS_REG(3, 0, 0, 5, 0) =20 /* * The RMI ABI only enables setting some GPRs and PC. The selection of GPRs @@ -754,6 +755,7 @@ static bool validate_realm_set_reg(struct kvm_vcpu *vcp= u, } else { switch (reg->id) { case KVM_REG_ARM_PMCR_EL0: + case KVM_REG_ARM_ID_AA64DFR0_EL1: return true; } } diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c index 01519d934d3a..76ff00488883 100644 --- a/arch/arm64/kvm/rmi.c +++ b/arch/arm64/kvm/rmi.c @@ -702,6 +702,7 @@ static int realm_create_rd(struct kvm *kvm) void *rd =3D NULL; phys_addr_t rd_phys, params_phys; size_t pgd_size =3D kvm_pgtable_stage2_pgd_size(kvm->arch.mmu.vtcr); + u64 dfr0 =3D kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1); int i, r; =20 realm->ia_bits =3D VTCR_EL2_IPA(kvm->arch.mmu.vtcr); @@ -728,6 +729,8 @@ static int realm_create_rd(struct kvm *kvm) params->rtt_level_start =3D get_start_level(realm); params->rtt_num_start =3D pgd_size / PAGE_SIZE; params->rtt_base =3D kvm->arch.mmu.pgd_phys; + params->num_bps =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0); + params->num_wps =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0); =20 if (kvm->arch.arm_pmu) { params->pmu_num_ctrs =3D kvm->arch.nr_pmu_counters; diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 83b5c36f43bf..ebb428b861f5 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2072,6 +2072,9 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu, { u8 debugver =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, DebugVer, val); u8 pmuver =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, val); + u8 bps =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, val); + u8 wps =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, val); + u8 ctx_cmps =3D SYS_FIELD_GET(ID_AA64DFR0_EL1, CTX_CMPs, val); =20 /* * Prior to commit 3d0dba5764b9 ("KVM: arm64: PMU: Move the @@ -2091,10 +2094,11 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcp= u, val &=3D ~ID_AA64DFR0_EL1_PMUVer_MASK; =20 /* - * 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; =20 if (ignore_feat_doublelock(vcpu, val)) { @@ -2329,10 +2333,11 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const = struct sys_reg_desc *rd, mutex_lock(&vcpu->kvm->arch.config_lock); =20 /* - * 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 !=3D read_id_reg(vcpu, rd)) ret =3D -EBUSY; else --=20 2.43.0