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 105b8aa0c0383b64323e7a95501555c2bd2b500b..e8f10daaa0d7a21540157c525120a49feea72f37 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -318,7 +318,13 @@ static void task_fpsimd_load(void)
 
 /*
  * Ensure FPSIMD/SVE storage in memory for the loaded context is up to
- * date with respect to the CPU registers.
+ * date with respect to the CPU registers. Note carefully that the
+ * current context is the context last bound to the CPU stored in
+ * 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, 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)
 {
@@ -334,9 +340,15 @@ static void fpsimd_save(void)
        if (test_thread_flag(TIF_FOREIGN_FPSTATE))
                return;
 
-       if (IS_ENABLED(CONFIG_ARM64_SVE) &&
-           test_thread_flag(TIF_SVE)) {
-               if (WARN_ON(sve_get_vl() != last->sve_vl)) {
+       if ((last->to_save == FP_STATE_CURRENT && test_thread_flag(TIF_SVE)) ||
+           last->to_save == FP_STATE_SVE) {
+               save_sve_regs = true;
+               vl = last->sve_vl;
+       }
+
+       if (IS_ENABLED(CONFIG_ARM64_SVE) && save_sve_regs) {
+               /* Get the configured VL from RDVL, will account for SM */
+               if (WARN_ON(sve_get_vl() != vl)) {
                        /*
                         * Can't save the user regs, so current would
                         * re-enter user with corrupt state.
@@ -347,26 +359,6 @@ static void fpsimd_save(void)
                }
        }
 
-       if (test_thread_flag(TIF_SVE)) {
-               save_sve_regs = 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 (IS_ENABLED(CONFIG_ARM64_SVE) && save_sve_regs) {
                sve_save_state((char *)last->sve_state +
                               sve_ffr_offset(last->sve_vl),

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 54a31c97eb7aa23d545d29e07bd889549325794c..2e0f44f4c470a7fc89ddcce708b4261150e8626f 100644 (file)
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -110,7 +110,6 @@ 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));
        }
 }
 
@@ -151,7 +150,5 @@ 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);
 }