linux-kernel - [PATCH v7 12/29] KVM: arm64: Define internal features for SME

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Message-Id: <20250822-kvm-arm64-sme-v7-12-7a65d82b8b10@kernel.org>
Date: Fri, 22 Aug 2025 02:53:41 +0100
From: Mark Brown <broonie@...nel.org>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
 Joey Gouly <joey.gouly@....com>, Catalin Marinas <catalin.marinas@....com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, Will Deacon <will@...nel.org>, 
 Paolo Bonzini <pbonzini@...hat.com>, Jonathan Corbet <corbet@....net>, 
 Shuah Khan <shuah@...nel.org>
Cc: Dave Martin <Dave.Martin@....com>, Fuad Tabba <tabba@...gle.com>, 
 Mark Rutland <mark.rutland@....com>, linux-arm-kernel@...ts.infradead.org, 
 kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
 linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Mark Brown <broonie@...nel.org>
Subject: [PATCH v7 12/29] KVM: arm64: Define internal features for SME

In order to simplify interdependencies in the rest of the series define
the feature detection for SME and it's subfeatures.  Due to the need for
vector length configuration we define a flag for SME like for SVE.  We
also have two subfeatures which add architectural state, FA64 and SME2,
which are configured via the normal ID register scheme.

Also provide helpers which check if the vCPU is in streaming mode or has
ZA enabled.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/kvm_host.h | 35 ++++++++++++++++++++++++++++++++++-
 arch/arm64/kvm/sys_regs.c         |  2 +-
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 88d184aac789..98761b601457 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -355,6 +355,8 @@ struct kvm_arch {
 #define KVM_ARCH_FLAG_GUEST_HAS_SVE			9
 	/* MIDR_EL1, REVIDR_EL1, and AIDR_EL1 are writable from userspace */
 #define KVM_ARCH_FLAG_WRITABLE_IMP_ID_REGS		10
+	/* SME exposed to guest */
+#define KVM_ARCH_FLAG_GUEST_HAS_SME			11
 	unsigned long flags;
 
 	/* VM-wide vCPU feature set */
@@ -1059,7 +1061,16 @@ struct kvm_vcpu_arch {
 #define vcpu_has_sve(vcpu)	kvm_has_sve((vcpu)->kvm)
 #endif
 
-#define vcpu_has_vec(vcpu) vcpu_has_sve(vcpu)
+#define kvm_has_sme(kvm)	(system_supports_sme() &&		\
+				 test_bit(KVM_ARCH_FLAG_GUEST_HAS_SME, &(kvm)->arch.flags))
+
+#ifdef __KVM_NVHE_HYPERVISOR__
+#define vcpu_has_sme(vcpu)	kvm_has_sme(kern_hyp_va((vcpu)->kvm))
+#else
+#define vcpu_has_sme(vcpu)	kvm_has_sme((vcpu)->kvm)
+#endif
+
+#define vcpu_has_vec(vcpu) (vcpu_has_sve(vcpu) || vcpu_has_sme(vcpu))
 
 #ifdef CONFIG_ARM64_PTR_AUTH
 #define vcpu_has_ptrauth(vcpu)						\
@@ -1705,6 +1716,28 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
 #define kvm_has_sctlr2(k)				\
 	(kvm_has_feat((k), ID_AA64MMFR3_EL1, SCTLRX, IMP))
 
+#define kvm_has_fa64(k)					\
+	(system_supports_fa64() &&			\
+	 kvm_has_feat((k), ID_AA64SMFR0_EL1, FA64, IMP))
+
+#define kvm_has_sme2(k)					\
+	(system_supports_sme2() &&			\
+	 kvm_has_feat((k), ID_AA64PFR1_EL1, SME, SME2))
+
+#ifdef __KVM_NVHE_HYPERVISOR__
+#define vcpu_has_sme2(vcpu)	kvm_has_sme2(kern_hyp_va((vcpu)->kvm))
+#define vcpu_has_fa64(vcpu)	kvm_has_fa64(kern_hyp_va((vcpu)->kvm))
+#else
+#define vcpu_has_sme2(vcpu)	kvm_has_sme2((vcpu)->kvm)
+#define vcpu_has_fa64(vcpu)	kvm_has_fa64((vcpu)->kvm)
+#endif
+
+#define vcpu_in_streaming_mode(vcpu) \
+	(__vcpu_sys_reg(vcpu, SVCR) & SVCR_SM_MASK)
+
+#define vcpu_za_enabled(vcpu) \
+	(__vcpu_sys_reg(vcpu, SVCR) & SVCR_ZA_MASK)
+
 static inline bool kvm_arch_has_irq_bypass(void)
 {
 	return true;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 82ffb3b3b3cf..111b07a78787 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1782,7 +1782,7 @@ static unsigned int sve_visibility(const struct kvm_vcpu *vcpu,
 static unsigned int sme_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
 {
-	if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SME, IMP))
+	if (vcpu_has_sme(vcpu))
 		return 0;
 
 	return REG_HIDDEN;

-- 
2.39.5