Hi Oliver, On Thu, Nov 4, 2021 at 9:14 AM Oliver Upton <oupton@xxxxxxxxxx> wrote: > > Hi Reiji, > > On Tue, Nov 02, 2021 at 11:24:54PM -0700, 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. > > Based on my understanding of the series, it appears that we require the > CPU identity to be the same amongst all vCPUs in a VM. Is there any > value in keeping a single copy in kvm_arch? Yes, that's a good point. It reminded me that the idea bothered me after we discussed a similar case about your counter offset patches, but I didn't seriously consider that. Thank you for bringing this up. I will look into keeping it per VM in kvm_arch. Regards, Reiji > > > Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx> > > --- > > arch/arm64/include/asm/kvm_host.h | 10 ++++++++++ > > arch/arm64/kvm/sys_regs.c | 24 ++++++++++++++++-------- > > 2 files changed, 26 insertions(+), 8 deletions(-) > > > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > > index 9b5e7a3b6011..0cd351099adf 100644 > > --- a/arch/arm64/include/asm/kvm_host.h > > +++ b/arch/arm64/include/asm/kvm_host.h > > @@ -145,6 +145,14 @@ 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 */ > > @@ -209,6 +217,8 @@ 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 1d46e185f31e..2443440720b4 100644 > > --- a/arch/arm64/kvm/sys_regs.c > > +++ b/arch/arm64/kvm/sys_regs.c > > @@ -273,7 +273,7 @@ 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 = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(SYS_ID_AA64MMFR1_EL1)); > > u32 sr = reg_to_encoding(r); > > > > if (!(val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))) { > > @@ -1059,12 +1059,11 @@ 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) > > { > > u32 id = reg_to_encoding(r); > > - u64 val = raz ? 0 : read_sanitised_ftr_reg(id); > > + u64 val = raz ? 0 : __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(id)); > > > > switch (id) { > > case SYS_ID_AA64PFR0_EL1: > > @@ -1174,6 +1173,16 @@ 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) > > @@ -1219,9 +1228,7 @@ 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. > > */ > > static int __get_id_reg(const struct kvm_vcpu *vcpu, > > const struct sys_reg_desc *rd, void __user *uaddr, > > @@ -1375,6 +1382,7 @@ 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, \ > > @@ -1830,8 +1838,8 @@ 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 = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(SYS_ID_AA64DFR0_EL1)); > > + u64 pfr = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(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) | > > -- > > 2.33.1.1089.g2158813163f-goog > >