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arm64/fpsimd: Stop using TIF_SVE to manage register saving in KVM

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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.

There should be no functional or performance impact from this change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221115094640.112848-5-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Brown 2022-11-15 09:46:36 +00:00 committed by Will Deacon
parent deeb8f9a80
commit 62021cc36a
2 changed files with 4 additions and 21 deletions
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22
arch/arm64/kernel/fpsimd.c
View File

@ -439,8 +439,8 @@ 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)
{
@ -457,27 +457,13 @@ 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_CURRENT && test_thread_flag(TIF_SVE)) ||
last->to_save == FP_STATE_SVE) {
save_sve_regs = true;
save_ffr = true;
vl = last->sve_vl;
}
/*
* Validate that an explicitly specified state to save is
* consistent with the task state.
*/
switch (last->to_save) {
case FP_STATE_CURRENT:
break;
case FP_STATE_FPSIMD:
WARN_ON_ONCE(save_sve_regs);
break;
case FP_STATE_SVE:
WARN_ON_ONCE(!save_sve_regs);
break;
}
if (system_supports_sme()) {
u64 *svcr = last->svcr;

3
arch/arm64/kvm/fpsimd.c
View File

@ -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);
}