Re: [PATCH v9 25/30] KVM: arm64: Expose SME to nested guests
From: Fuad Tabba <tabba@google.com>
Date: 2026-01-13 14:38:36
Also in:
kvm, kvmarm, linux-arm-kernel, linux-kselftest, lkml
On Tue, 23 Dec 2025 at 01:23, Mark Brown [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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@kernel.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 |
Should we also limit this to SME2, i.e. + val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64PFR1_EL1, SME, SME2); That said, we don't do anything similar to SVE, but it might also be worth doing that there. Reviewed-by: Fuad Tabba <tabba@google.com> Cheers, /fuad
ID_AA64PFR1_EL1_RES0 |
ID_AA64PFR1_EL1_MPAM_frac |
ID_AA64PFR1_EL1_MTE);
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2.47.3