[PATCH RFC v3 18/27] KVM: arm64: Support SMIDR_EL1 for guests

[Mark Brown <broonie@kernel.org>]

SME adds an identification register SMIDR_EL1 which provides a basic
description of the SME implementation, describing the implementation
in a manner similar to MIDR_EL1 for the PE as well as indicating support
for priority management.

Since we do not currently support SME priority control we mask out SMPS,
indicating that priority management is not supported.  We do the same
for Affinity, indicating that there is no physical sharing, and unknown
fields.

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, 44 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 063b75eb4f3bc4fb425d2abc8118a950bccc2317..a304b02efcadba5371edffe97e911bba0634ed62 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -472,6 +472,7 @@ 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 b5a38fc7a4a9ed4fce053018eb6ff353ae5c0d09..416c855153ca532e4c6557d78599e9af0f913071 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -882,6 +882,39 @@ 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 any priority or affinity information, or fields we
+	 * don't know about.
+	 */
+	smidr &= ~(SMIDR_EL1_SMPS_MASK | SMIDR_EL1_AFFINITY_MASK |
+		   SMIDR_EL1_RES0);
+
+	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)
 {
@@ -1576,7 +1609,9 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
 		if (!kvm_has_mte(vcpu->kvm))
 			val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE);
 
-		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_MTE_frac);
@@ -1676,6 +1711,10 @@ 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;
@@ -2601,7 +2640,7 @@ 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),
 
@@ -2799,7 +2838,8 @@ 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 },
 	{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
 	ID_FILTERED(CTR_EL0, ctr_el0,
 		    CTR_EL0_DIC_MASK |

-- 
2.39.5