Patch "KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN" has been added to the 6.13-stable tree
gregkh at linuxfoundation.org
gregkh at linuxfoundation.org
Mon Mar 24 11:56:28 PDT 2025
This is a note to let you know that I've just added the patch titled
KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.zen.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.
>From stable+bounces-125701-greg=kroah.com at vger.kernel.org Thu Mar 20 17:12:02 2025
From: Mark Brown <broonie at kernel.org>
Date: Fri, 21 Mar 2025 00:10:13 +0000
Subject: KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN
To: Greg Kroah-Hartman <gregkh at linuxfoundation.org>, Marc Zyngier <maz at kernel.org>, Oliver Upton <oliver.upton at linux.dev>, Joey Gouly <joey.gouly at arm.com>, Suzuki K Poulose <suzuki.poulose at arm.com>, Catalin Marinas <catalin.marinas at arm.com>, Will Deacon <will at kernel.org>
Cc: linux-arm-kernel at lists.infradead.org, kvmarm at lists.linux.dev, linux-kernel at vger.kernel.org, stable at vger.kernel.org, Mark Brown <broonie at kernel.org>, Mark Rutland <mark.rutland at arm.com>, Fuad Tabba <tabba at google.com>
Message-ID: <20250321-stable-sve-6-13-v2-4-3150e3370c40 at kernel.org>
From: Mark Rutland <mark.rutland at arm.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 at arm.com>
Reviewed-by: Mark Brown <broonie at kernel.org>
Tested-by: Mark Brown <broonie at kernel.org>
Acked-by: Will Deacon <will at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Fuad Tabba <tabba at google.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Oliver Upton <oliver.upton at linux.dev>
Reviewed-by: Oliver Upton <oliver.upton at linux.dev>
Link: https://lore.kernel.org/r/20250210195226.1215254-4-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz at kernel.org>
[Rework for refactoring of where the flags are stored -- broonie]
Signed-off-by: Mark Brown <broonie at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
arch/arm64/include/asm/kvm_host.h | 2 --
arch/arm64/kvm/fpsimd.c | 16 ----------------
2 files changed, 18 deletions(-)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -902,8 +902,6 @@ struct kvm_vcpu_arch {
/* Save TRBE context if active */
#define DEBUG_STATE_SAVE_TRBE __vcpu_single_flag(iflags, BIT(6))
-/* SVE enabled for host EL0 */
-#define HOST_SVE_ENABLED __vcpu_single_flag(sflags, BIT(0))
/* SME enabled for EL0 */
#define HOST_SME_ENABLED __vcpu_single_flag(sflags, BIT(1))
/* Physical CPU not in supported_cpus */
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -65,10 +65,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vc
fpsimd_save_and_flush_cpu_state();
*host_data_ptr(fp_owner) = FP_STATE_FREE;
- vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
- if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
- vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
-
if (system_supports_sme()) {
vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
@@ -202,18 +198,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcp
* when needed.
*/
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 by kvm_reset_cptr_el2() in the Hyp code, disabling SVE
- * for EL0. To avoid spurious traps, restore the trap state
- * seen by kvm_arch_vcpu_load_fp():
- */
- if (vcpu_get_flag(vcpu, 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);
Patches currently in stable-queue which might be from broonie at kernel.org are
queue-6.13/kvm-arm64-calculate-cptr_el2-traps-on-activating-traps.patch
queue-6.13/regulator-check-that-dummy-regulator-has-been-probed-before-using-it.patch
queue-6.13/kvm-arm64-eagerly-switch-zcr_el-1-2.patch
queue-6.13/kvm-arm64-mark-some-header-functions-as-inline.patch
queue-6.13/kvm-arm64-remove-host-fpsimd-saving-for-non-protected-kvm.patch
queue-6.13/regulator-dummy-force-synchronous-probing.patch
queue-6.13/kvm-arm64-refactor-exit-handlers.patch
queue-6.13/kvm-arm64-unconditionally-save-flush-host-fpsimd-sve-sme-state.patch
queue-6.13/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.smen.patch
queue-6.13/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.zen.patch
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