linux-kernel - [PATCH v9 25/30] KVM: arm64: Expose SME to nested guests

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Message-Id: <20251223-kvm-arm64-sme-v9-25-8be3867cb883@kernel.org>
Date: Tue, 23 Dec 2025 01:21:19 +0000
From: Mark Brown <broonie@...nel.org>
To: Marc Zyngier <maz@...nel.org>, 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>, Oliver Upton <oupton@...nel.org>
Cc: Dave Martin <Dave.Martin@....com>, Fuad Tabba <tabba@...gle.com>, 
 Mark Rutland <mark.rutland@....com>, Ben Horgan <ben.horgan@....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, 
 Peter Maydell <peter.maydell@...aro.org>, 
 Eric Auger <eric.auger@...hat.com>, Mark Brown <broonie@...nel.org>
Subject: [PATCH v9 25/30] KVM: arm64: Expose SME to nested guests

With support for context switching SME state in place allow access to SME
in nested guests.

The SME floating point state is handled along with all the other floating
point state, SME specific floating point exceptions are directed into the
same handlers as other floating point exceptions with NV specific handling
for the vector lengths already in place.

TPIDR2_EL0 is context switched along with the other TPIDRs as part of the
main guest register context switch.

SME priority support is currently masked from all guests including nested
ones.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/kvm/nested.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index cdeeb8f09e72..a0967ca8c61e 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1534,14 +1534,13 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)
 		break;
 
 	case SYS_ID_AA64PFR1_EL1:
-		/* Only support BTI, SSBS, CSV2_frac */
+		/* Only support BTI, SME, SSBS, CSV2_frac */
 		val &= ~(ID_AA64PFR1_EL1_PFAR		|
 			 ID_AA64PFR1_EL1_MTEX		|
 			 ID_AA64PFR1_EL1_THE		|
 			 ID_AA64PFR1_EL1_GCS		|
 			 ID_AA64PFR1_EL1_MTE_frac	|
 			 ID_AA64PFR1_EL1_NMI		|
-			 ID_AA64PFR1_EL1_SME		|
 			 ID_AA64PFR1_EL1_RES0		|
 			 ID_AA64PFR1_EL1_MPAM_frac	|
 			 ID_AA64PFR1_EL1_MTE);

-- 
2.47.3