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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id p2sm6221778wmq.23.2021.11.24.10.08.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Nov 2021 10:08:53 -0800 (PST) Subject: Re: [RFC PATCH v3 02/29] KVM: arm64: Save ID registers' sanitized value per vCPU To: Reiji Watanabe References: <20211117064359.2362060-1-reijiw@google.com> <20211117064359.2362060-3-reijiw@google.com> From: Eric Auger Message-ID: <4193e1b3-3cc2-7e9a-e249-75ef71495398@redhat.com> Date: Wed, 24 Nov 2021 19:08:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eauger@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Cc: kvm@vger.kernel.org, Marc Zyngier , Peter Shier , Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Reiji, On 11/18/21 11:00 PM, Reiji Watanabe wrote: > Hi Eric, > > On Thu, Nov 18, 2021 at 12:37 PM Eric Auger wrote: >> >> Hi Reiji, >> >> On 11/17/21 7:43 AM, Reiji Watanabe wrote: >>> Extend sys_regs[] of kvm_cpu_context for ID registers and save ID >>> registers' sanitized value in the array for the vCPU at the first >>> vCPU reset. Use the saved ones when ID registers are read by >>> userspace (via KVM_GET_ONE_REG) or the guest. >>> >>> Signed-off-by: Reiji Watanabe >>> --- >>> arch/arm64/include/asm/kvm_host.h | 10 +++++++ >>> arch/arm64/kvm/sys_regs.c | 43 +++++++++++++++++++------------ >>> 2 files changed, 37 insertions(+), 16 deletions(-) >>> >>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>> index edbe2cb21947..72db73c79403 100644 >>> --- a/arch/arm64/include/asm/kvm_host.h >>> +++ b/arch/arm64/include/asm/kvm_host.h >>> @@ -146,6 +146,14 @@ struct kvm_vcpu_fault_info { >>> u64 disr_el1; /* Deferred [SError] Status Register */ >>> }; >>> >>> +/* >>> + * (Op0, Op1, CRn, CRm, Op2) of ID registers is (3, 0, 0, crm, op2), >>> + * where 0<=crm<8, 0<=op2<8. >>> + */ >>> +#define KVM_ARM_ID_REG_MAX_NUM 64 >>> +#define IDREG_IDX(id) ((sys_reg_CRm(id) << 3) | sys_reg_Op2(id)) >>> +#define IDREG_SYS_IDX(id) (ID_REG_BASE + IDREG_IDX(id)) >>> + >>> enum vcpu_sysreg { >>> __INVALID_SYSREG__, /* 0 is reserved as an invalid value */ >>> MPIDR_EL1, /* MultiProcessor Affinity Register */ >>> @@ -210,6 +218,8 @@ enum vcpu_sysreg { >>> CNTP_CVAL_EL0, >>> CNTP_CTL_EL0, >>> >>> + ID_REG_BASE, >>> + ID_REG_END = ID_REG_BASE + KVM_ARM_ID_REG_MAX_NUM - 1, >>> /* Memory Tagging Extension registers */ >>> RGSR_EL1, /* Random Allocation Tag Seed Register */ >>> GCR_EL1, /* Tag Control Register */ >>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c >>> index e3ec1a44f94d..5608d3410660 100644 >>> --- a/arch/arm64/kvm/sys_regs.c >>> +++ b/arch/arm64/kvm/sys_regs.c >>> @@ -33,6 +33,8 @@ >>> >>> #include "trace.h" >>> >>> +static u64 __read_id_reg(const struct kvm_vcpu *vcpu, u32 id); >>> + >>> /* >>> * All of this file is extremely similar to the ARM coproc.c, but the >>> * types are different. My gut feeling is that it should be pretty >>> @@ -273,7 +275,7 @@ static bool trap_loregion(struct kvm_vcpu *vcpu, >>> struct sys_reg_params *p, >>> const struct sys_reg_desc *r) >>> { >>> - u64 val = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1); >>> + u64 val = __read_id_reg(vcpu, SYS_ID_AA64MMFR1_EL1); >>> u32 sr = reg_to_encoding(r); >>> >>> if (!(val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))) { >>> @@ -1059,17 +1061,9 @@ static bool access_arch_timer(struct kvm_vcpu *vcpu, >>> return true; >>> } >>> >>> -/* Read a sanitised cpufeature ID register by sys_reg_desc */ >>> -static u64 read_id_reg(const struct kvm_vcpu *vcpu, >>> - struct sys_reg_desc const *r, bool raz) >>> +static u64 __read_id_reg(const struct kvm_vcpu *vcpu, u32 id) >>> { >>> - u32 id = reg_to_encoding(r); >>> - u64 val; >>> - >>> - if (raz) >>> - return 0; >>> - >>> - val = read_sanitised_ftr_reg(id); >>> + u64 val = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(id)); >>> >>> switch (id) { >>> case SYS_ID_AA64PFR0_EL1: >>> @@ -1119,6 +1113,14 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, >>> return val; >>> } >>> >>> +static u64 read_id_reg(const struct kvm_vcpu *vcpu, >>> + struct sys_reg_desc const *r, bool raz) >>> +{ >>> + u32 id = reg_to_encoding(r); >>> + >>> + return raz ? 0 : __read_id_reg(vcpu, id); >>> +} >>> + >>> static unsigned int id_visibility(const struct kvm_vcpu *vcpu, >>> const struct sys_reg_desc *r) >>> { >>> @@ -1178,6 +1180,16 @@ static unsigned int sve_visibility(const struct kvm_vcpu *vcpu, >>> return REG_HIDDEN; >>> } >>> >>> +static void reset_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd) >>> +{ >>> + u32 id = reg_to_encoding(rd); >>> + >>> + if (vcpu_has_reset_once(vcpu)) >>> + return; >>> + >>> + __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(id)) = read_sanitised_ftr_reg(id); >>> +} >>> + >>> static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, >>> const struct sys_reg_desc *rd, >>> const struct kvm_one_reg *reg, void __user *uaddr) >>> @@ -1223,9 +1235,7 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, >>> /* >>> * cpufeature ID register user accessors >>> * >>> - * For now, these registers are immutable for userspace, so no values >>> - * are stored, and for set_id_reg() we don't allow the effective value >>> - * to be changed. >>> + * We don't allow the effective value to be changed. >> This change may be moved to a subsequent patch as this patch does not >> change the behavior yet. > > Thank you for the review. > > There are three main parts in the original comments. > > (A) these registers are immutable for userspace > (B) no values are stored > (C) we don't allow the effective value to be changed > > This patch stores ID register values in sys_regs[]. > So, I don't think (B) should be there, and I removed (B). > Since (A) is essentially the same as (C), I removed (A) > (and left (C)). > > Do you think it is better to leave (A) in this patch, too ? yes I think I would leave 'for now, these registers are immutable for userspace' Eric > > Thanks, > Reiji > > >>> */ >>> static int __get_id_reg(const struct kvm_vcpu *vcpu, >>> const struct sys_reg_desc *rd, void __user *uaddr, >>> @@ -1382,6 +1392,7 @@ static unsigned int mte_visibility(const struct kvm_vcpu *vcpu, >>> #define ID_SANITISED(name) { \ >>> SYS_DESC(SYS_##name), \ >>> .access = access_id_reg, \ >>> + .reset = reset_id_reg, \ >>> .get_user = get_id_reg, \ >>> .set_user = set_id_reg, \ >>> .visibility = id_visibility, \ >>> @@ -1837,8 +1848,8 @@ static bool trap_dbgdidr(struct kvm_vcpu *vcpu, >>> if (p->is_write) { >>> return ignore_write(vcpu, p); >>> } else { >>> - u64 dfr = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1); >>> - u64 pfr = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); >>> + u64 dfr = __read_id_reg(vcpu, SYS_ID_AA64DFR0_EL1); >>> + u64 pfr = __read_id_reg(vcpu, SYS_ID_AA64PFR0_EL1); >>> u32 el3 = !!cpuid_feature_extract_unsigned_field(pfr, ID_AA64PFR0_EL3_SHIFT); >>> >>> p->regval = ((((dfr >> ID_AA64DFR0_WRPS_SHIFT) & 0xf) << 28) | >>> >> Thanks >> >> Eric >> > _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm