The primary register for identifying SME is ID_AA64PFR1_EL1.SME. This is hidden from guests unless SME is enabled by the VMM. When it is visible it is writable and can be used to control the availability of SME2.
There is also a new register ID_AA64SMFR0_EL1 which we make writable, forcing it to all bits 0 if SME is disabled. This includes the field SMEver giving the SME version, userspace is responsible for ensuring the value is consistent with ID_AA64PFR1_EL1.SME. It also includes FA64, a separately enableable extension which provides the full FPSIMD and SVE instruction set including FFR in streaming mode. Userspace can control the availability of FA64 by writing to this field. The other features enumerated there only add new instructions, there are no architectural controls for these.
There is a further identification register SMIDR_EL1 which provides a basic description of the SME microarchitecture, in a manner similar to MIDR_EL1 for the PE. It also describes support for priority management and a basic affinity description for shared SME units, plus some RES0 space. We do not support priority management and affinity is not meaningful for guests so we mask out everything except for the microarchitecture description.
As for MIDR_EL1 and REVIDR_EL1 we expose the implementer and revision information to guests with the raw value from the CPU we are running on, this may present issues for asymmetric systems or for migration as it does for the existing registers.
Signed-off-by: Mark Brown broonie@kernel.org --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/sys_regs.c | 46 +++++++++++++++++++++++++++++++++++---- 2 files changed, 43 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index c26099f74648..29b8697c8144 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -494,6 +494,7 @@ enum vcpu_sysreg { /* FP/SIMD/SVE */ SVCR, FPMR, + SMIDR_EL1, /* Streaming Mode Identification Register */
/* 32bit specific registers. */ DACR32_EL2, /* Domain Access Control Register */ diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index caa90dae8184..b11bb95e9e35 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -774,6 +774,38 @@ static u64 reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) return mpidr; }
+static u64 reset_smidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) +{ + u64 smidr = 0; + + if (!system_supports_sme()) + return smidr; + + smidr = read_sysreg_s(SYS_SMIDR_EL1); + + /* + * Mask out everything except for the implementer and revison, + * in particular priority management is not implemented. + */ + smidr &= SMIDR_EL1_IMPLEMENTER_MASK | SMIDR_EL1_REVISION_MASK; + + vcpu_write_sys_reg(vcpu, smidr, SMIDR_EL1); + + return smidr; +} + +static bool access_smidr(struct kvm_vcpu *vcpu, + struct sys_reg_params *p, + const struct sys_reg_desc *r) +{ + if (p->is_write) + return write_to_read_only(vcpu, p, r); + + p->regval = vcpu_read_sys_reg(vcpu, r->reg); + + return true; +} + static unsigned int pmu_visibility(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) { @@ -1607,7 +1639,9 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu, val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE_frac); }
- val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME); + if (!vcpu_has_sme(vcpu)) + val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME); + val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RNDR_trap); val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI); val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_GCS); @@ -1723,6 +1757,10 @@ static unsigned int id_visibility(const struct kvm_vcpu *vcpu, if (!vcpu_has_sve(vcpu)) return REG_RAZ; break; + case SYS_ID_AA64SMFR0_EL1: + if (!vcpu_has_sme(vcpu)) + return REG_RAZ; + break; }
return 0; @@ -2905,7 +2943,6 @@ static const struct sys_reg_desc sys_reg_descs[] = { ID_AA64PFR1_EL1_MTE_frac | ID_AA64PFR1_EL1_NMI | ID_AA64PFR1_EL1_RNDR_trap | - ID_AA64PFR1_EL1_SME | ID_AA64PFR1_EL1_RES0 | ID_AA64PFR1_EL1_MPAM_frac | ID_AA64PFR1_EL1_RAS_frac | @@ -2913,7 +2950,7 @@ static const struct sys_reg_desc sys_reg_descs[] = { ID_WRITABLE(ID_AA64PFR2_EL1, ID_AA64PFR2_EL1_FPMR), ID_UNALLOCATED(4,3), ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0), - ID_HIDDEN(ID_AA64SMFR0_EL1), + ID_WRITABLE(ID_AA64SMFR0_EL1, ~ID_AA64SMFR0_EL1_RES0), ID_UNALLOCATED(4,6), ID_WRITABLE(ID_AA64FPFR0_EL1, ~ID_AA64FPFR0_EL1_RES0),
@@ -3112,7 +3149,8 @@ static const struct sys_reg_desc sys_reg_descs[] = { { SYS_DESC(SYS_CLIDR_EL1), access_clidr, reset_clidr, CLIDR_EL1, .set_user = set_clidr, .val = ~CLIDR_EL1_RES0 }, { SYS_DESC(SYS_CCSIDR2_EL1), undef_access }, - { SYS_DESC(SYS_SMIDR_EL1), undef_access }, + { SYS_DESC(SYS_SMIDR_EL1), .access = access_smidr, .reset = reset_smidr, + .reg = SMIDR_EL1, .visibility = sme_visibility }, IMPLEMENTATION_ID(AIDR_EL1, GENMASK_ULL(63, 0)), { SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 }, ID_FILTERED(CTR_EL0, ctr_el0,