On Mon, 15 Aug 2022 23:55:26 +0100,
Mark Brown <broonie@xxxxxxxxxx> wrote:
>
> Now that we are explicitly telling the host FP code which register state
> it needs to save we can remove the manipulation of TIF_SVE from the KVM
> code, simplifying it and allowing us to optimise our handling of normal
> tasks. Remove the manipulation of TIF_SVE from KVM and instead rely on
> to_save to ensure we save the correct data for it.
>
> Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
> ---
> arch/arm64/kernel/fpsimd.c | 22 ++++------------------
> arch/arm64/kvm/fpsimd.c | 3 ---
> 2 files changed, 4 insertions(+), 21 deletions(-)
>
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index 7be20ced2c45..aaea2dc02cbd 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -436,8 +436,8 @@ static void task_fpsimd_load(void)
> * last, if KVM is involved this may be the guest VM context rather
> * than the host thread for the VM pointed to by current. This means
> * that we must always reference the state storage via last rather
> - * than via current, other than the TIF_ flags which KVM will
> - * carefully maintain for us.
> + * than via current, if we are saving KVM state then it will have
> + * ensured that the type of registers to save is set in last->to_save.
> */
> static void fpsimd_save(void)
> {
> @@ -454,27 +454,13 @@ static void fpsimd_save(void)
> if (test_thread_flag(TIF_FOREIGN_FPSTATE))
> return;
>
> - if (test_thread_flag(TIF_SVE)) {
> + if ((last->to_save == FP_STATE_TASK && test_thread_flag(TIF_SVE)) ||
> + last->to_save == FP_STATE_SVE) {
> save_sve_regs = true;
> save_ffr = true;
> vl = last->sve_vl;
> }
>
> - /*
> - * For now we're just validating that the requested state is
> - * consistent with what we'd otherwise work out.
> - */
> - switch (last->to_save) {
> - case FP_STATE_TASK:
> - break;
> - case FP_STATE_FPSIMD:
> - WARN_ON_ONCE(save_sve_regs);
> - break;
> - case FP_STATE_SVE:
> - WARN_ON_ONCE(!save_sve_regs);
> - break;
> - }
> -
Given how short-lived this code is, consider dropping it altogether.
Actually, the previous patch would make a lot more sense if it was
merged with this one.
> if (system_supports_sme()) {
> u64 *svcr = last->svcr;
>
> diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
> index db0b2bacaeb8..8a79823fce68 100644
> --- a/arch/arm64/kvm/fpsimd.c
> +++ b/arch/arm64/kvm/fpsimd.c
> @@ -151,7 +151,6 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
> &vcpu->arch.fp_type, fp_type);
>
> clear_thread_flag(TIF_FOREIGN_FPSTATE);
> - update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
> }
> }
>
> @@ -208,7 +207,5 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
> sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
> }
>
> - update_thread_flag(TIF_SVE, 0);
> -
> local_irq_restore(flags);
> }
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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