[PATCH] KVM: arm64: Synchronize SMEN on vcpu schedule out

[PATCH] KVM: arm64: Synchronize SMEN on vcpu schedule out

[Dong Bo]

From: Nianyao Tang <tangnianyao@huawei.com>

If we have VHE and need to reenable SME for host in
kvm_arch_vcpu_put_fp, CPACR.SMEN is modified from 0 to 1. Trap
control for reading SVCR is modified from enable to disable.
Synchronization is needed before reading SVCR later in
fpsimd_save, or it may cause sync exception which can not be
handled by host.

Cc: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
---
 arch/arm64/kvm/fpsimd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 02dd7e9ebd39..f5799f571317 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -184,6 +184,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 			sysreg_clear_set(CPACR_EL1,
 					 CPACR_EL1_SMEN_EL0EN,
 					 CPACR_EL1_SMEN_EL1EN);
+		isb();
 	}
 
 	if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
-- 
1.8.3.1


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Re: [PATCH] KVM: arm64: Synchronize SMEN on vcpu schedule out

[Marc Zyngier]

+ Mark

On Tue, 20 Dec 2022 10:50:24 +0000,
Dong Bo <dongbo4@huawei.com> wrote:
> 
> From: Nianyao Tang <tangnianyao@huawei.com>
> 
> If we have VHE and need to reenable SME for host in
> kvm_arch_vcpu_put_fp, CPACR.SMEN is modified from 0 to 1. Trap
> control for reading SVCR is modified from enable to disable.
> Synchronization is needed before reading SVCR later in
> fpsimd_save, or it may cause sync exception which can not be
> handled by host.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: James Morse <james.morse@arm.com>
> Cc: Alexandru Elisei <alexandru.elisei@arm.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Oliver Upton <oliver.upton@linux.dev>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
> ---
>  arch/arm64/kvm/fpsimd.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
> index 02dd7e9ebd39..f5799f571317 100644
> --- a/arch/arm64/kvm/fpsimd.c
> +++ b/arch/arm64/kvm/fpsimd.c
> @@ -184,6 +184,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
>  			sysreg_clear_set(CPACR_EL1,
>  					 CPACR_EL1_SMEN_EL0EN,
>  					 CPACR_EL1_SMEN_EL1EN);
> +		isb();
>  	}
>  
>  	if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
> -- 
> 1.8.3.1
> 
> 

-- 
Without deviation from the norm, progress is not possible.

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Re: [PATCH] KVM: arm64: Synchronize SMEN on vcpu schedule out

[Mark Brown]

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On Tue, Dec 20, 2022 at 10:15:18AM +0000, Marc Zyngier wrote:
> Dong Bo <dongbo4@huawei.com> wrote:

> > If we have VHE and need to reenable SME for host in
> > kvm_arch_vcpu_put_fp, CPACR.SMEN is modified from 0 to 1. Trap
> > control for reading SVCR is modified from enable to disable.
> > Synchronization is needed before reading SVCR later in
> > fpsimd_save, or it may cause sync exception which can not be
> > handled by host.

Reviewed-by: Mark Brown <broonie@kernel.org>

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Re: [PATCH] KVM: arm64: Synchronize SMEN on vcpu schedule out

[Oliver Upton]

On Tue, 20 Dec 2022 18:50:24 +0800, Dong Bo wrote:
> From: Nianyao Tang <tangnianyao@huawei.com>
> 
> If we have VHE and need to reenable SME for host in
> kvm_arch_vcpu_put_fp, CPACR.SMEN is modified from 0 to 1. Trap
> control for reading SVCR is modified from enable to disable.
> Synchronization is needed before reading SVCR later in
> fpsimd_save, or it may cause sync exception which can not be
> handled by host.
> 
> [...]

Applied to kvmarm/next, thanks!

[1/1] KVM: arm64: Synchronize SMEN on vcpu schedule out
      https://git.kernel.org/kvmarm/kvmarm/c/59d78a2ec0e9

--
Best,
Oliver

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