[PATCH v2 4/7] arm64/fpsimd: Stop using TIF_SVE to manage register saving in KVM

[Mark Brown <broonie@kernel.org>]

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@kernel.org>
---
 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 95c95411bd42..ebe66d8c66e8 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -435,8 +435,8 @@ 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)
 {
@@ -453,27 +453,13 @@ 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;
-	}
-
 	if (system_supports_sme()) {
 		u64 *svcr = last->svcr;
 		*svcr = read_sysreg_s(SYS_SVCR);
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 542c71b16451..54131a57130e 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -150,7 +150,6 @@ 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));
 	}
 }
 
@@ -207,7 +206,5 @@ 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);
 }
-- 
2.30.2

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