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Message-Id: <20250403-stable-sve-5-15-v2-8-30a36a78a20a@kernel.org>
Date: Thu, 03 Apr 2025 00:20:23 +0100
From: Mark Brown <broonie@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Oleg Nesterov <oleg@...hat.com>, Oliver Upton <oliver.upton@...ux.dev>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Mark Brown <broonie@...nel.org>, Mark Rutland <mark.rutland@....com>,
Fuad Tabba <tabba@...gle.com>
Subject: [PATCH 5.15 v2 08/10] KVM: arm64: Remove VHE host restore of
CPACR_EL1.ZEN
From: Mark Rutland <mark.rutland@....com>
[ Upstream commit 459f059be702056d91537b99a129994aa6ccdd35 ]
When KVM is in VHE mode, the host kernel tries to save and restore the
configuration of CPACR_EL1.ZEN (i.e. CPTR_EL2.ZEN when HCR_EL2.E2H=1)
across kvm_arch_vcpu_load_fp() and kvm_arch_vcpu_put_fp(), since the
configuration may be clobbered by hyp when running a vCPU. This logic is
currently redundant.
The VHE hyp code unconditionally configures CPTR_EL2.ZEN to 0b01 when
returning to the host, permitting host kernel usage of SVE.
Now that the host eagerly saves and unbinds its own FPSIMD/SVE/SME
state, there's no need to save/restore the state of the EL0 SVE trap.
The kernel can safely save/restore state without trapping, as described
above, and will restore userspace state (including trap controls) before
returning to userspace.
Remove the redundant logic.
Signed-off-by: Mark Rutland <mark.rutland@....com>
Reviewed-by: Mark Brown <broonie@...nel.org>
Tested-by: Mark Brown <broonie@...nel.org>
Acked-by: Will Deacon <will@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Fuad Tabba <tabba@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Oliver Upton <oliver.upton@...ux.dev>
Reviewed-by: Oliver Upton <oliver.upton@...ux.dev>
Link: https://lore.kernel.org/r/20250210195226.1215254-4-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz@...nel.org>
[Rework for refactoring of where the flags are stored -- broonie]
Signed-off-by: Mark Brown <broonie@...nel.org>
---
arch/arm64/include/asm/kvm_host.h | 1 -
arch/arm64/kvm/fpsimd.c | 15 ---------------
2 files changed, 16 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 06e8d4645ecd..3d4e2396a2d7 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -421,7 +421,6 @@ struct kvm_vcpu_arch {
#define KVM_ARM64_DEBUG_DIRTY (1 << 0)
#define KVM_ARM64_FP_ENABLED (1 << 1) /* guest FP regs loaded */
#define KVM_ARM64_FP_HOST (1 << 2) /* host FP regs loaded */
-#define KVM_ARM64_HOST_SVE_ENABLED (1 << 4) /* SVE enabled for EL0 */
#define KVM_ARM64_GUEST_HAS_SVE (1 << 5) /* SVE exposed to guest */
#define KVM_ARM64_VCPU_SVE_FINALIZED (1 << 6) /* SVE config completed */
#define KVM_ARM64_GUEST_HAS_PTRAUTH (1 << 7) /* PTRAUTH exposed to guest */
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 1ef9d6cb91ee..1360ddd4137b 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -83,9 +83,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
*/
fpsimd_save_and_flush_cpu_state();
vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
-
- if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
- vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
}
/*
@@ -142,18 +139,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
}
fpsimd_save_and_flush_cpu_state();
- } else if (has_vhe() && system_supports_sve()) {
- /*
- * The FPSIMD/SVE state in the CPU has not been touched, and we
- * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
- * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
- * for EL0. To avoid spurious traps, restore the trap state
- * seen by kvm_arch_vcpu_load_fp():
- */
- if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
- sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
- else
- sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
}
local_irq_restore(flags);
--
2.39.5
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