[PATCH v1 4/7] arm64/fpsimd: Stop using TIF_SVE to manage register saving in KVM

[Mark Brown]

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 <broo...@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 f23be4247e75..aa23bd855414 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -433,8 +433,8 @@ 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)
 {
@@ -451,27 +451,13 @@ 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 b614aa3f8266..77af63e0b177 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -148,7 +148,6 @@ 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));
        }
 }
 
@@ -205,7 +204,5 @@ 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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