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

[ Upstream commit 62021cc36add7b2c015b837f7893f2fb4b8c2586 ]

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>
[ Mark: trivial backport ]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 1f6fd9229e536966292a9751f08103912a48ba07..3fcacbce5d427e274a9439b8a6f9edf4080d54a4 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -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;
 

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 89c02ce797b874196eff978464a936dfb020ad02..ec82d0191f76717ad17a43f87bd8a806eb4ab3b8 100644 (file)
--- 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);
 }