Add last_fpsimd_trap to notify if guest last exit reason is handling fpsimd. If 
guest is using fpsimd frequently, save host's fpsimd state and restore guest's 
fpsimd state and deactive fpsimd trap before returning to guest. It can avoid 
guest fpsimd trap soon to improve performance.

Signed-off-by: Nianyao Tang <tangnian...@huawei.com>
---
 arch/arm64/kernel/asm-offsets.c |  1 +
 arch/arm64/kvm/hyp/entry.S      |  5 +++++
 arch/arm64/kvm/hyp/switch.c     | 38 ++++++++++++++++++++++++++++++++++++--
 include/linux/kvm_host.h        |  1 +
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c 
index 5bdda65..35a9c5c 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -136,6 +136,7 @@ int main(void)
 #ifdef CONFIG_KVM_ARM_HOST
   DEFINE(VCPU_CONTEXT,         offsetof(struct kvm_vcpu, arch.ctxt));
   DEFINE(VCPU_FAULT_DISR,      offsetof(struct kvm_vcpu, arch.fault.disr_el1));
+  DEFINE(VCPU_LAST_FPSIMD_TRAP, offsetof(struct kvm_vcpu, 
+ last_fpsimd_trap));
   DEFINE(CPU_GP_REGS,          offsetof(struct kvm_cpu_context, gp_regs));
   DEFINE(CPU_USER_PT_REGS,     offsetof(struct kvm_regs, regs));
   DEFINE(CPU_FP_REGS,          offsetof(struct kvm_regs, fp_regs));
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index 
e41a161..956e042 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -197,6 +197,11 @@ alternative_endif
        add     x0, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
        bl      __fpsimd_restore_state
 
+       // Mark guest using fpsimd now
+       ldr x0, [x3, #VCPU_LAST_FPSIMD_TRAP]
+       add x0, x0, #1
+       str x0, [x3, #VCPU_LAST_FPSIMD_TRAP]
+
        // Skip restoring fpexc32 for AArch64 guests
        mrs     x1, hcr_el2
        tbnz    x1, #HCR_RW_SHIFT, 1f
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c index 
d964523..86eea1b 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -92,7 +92,13 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
 
        val = read_sysreg(cpacr_el1);
        val |= CPACR_EL1_TTA;
-       val &= ~(CPACR_EL1_FPEN | CPACR_EL1_ZEN);
+       val &= ~CPACR_EL1_ZEN;
+
+       if (vcpu->last_fpsimd_trap)
+               val |= CPACR_EL1_FPEN;
+       else
+               val &= ~CPACR_EL1_FPEN;
+
        write_sysreg(val, cpacr_el1);
 
        write_sysreg(kvm_get_hyp_vector(), vbar_el1); @@ -105,7 +111,13 @@ 
static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
        __activate_traps_common(vcpu);
 
        val = CPTR_EL2_DEFAULT;
-       val |= CPTR_EL2_TTA | CPTR_EL2_TFP | CPTR_EL2_TZ;
+       val |= CPTR_EL2_TTA | CPTR_EL2_TZ;
+
+       if (vcpu->last_fpsimd_trap)
+               val &= ~CPTR_EL2_TFP;
+       else
+               val |= CPTR_EL2_TFP;
+
        write_sysreg(val, cptr_el2);
 }
 
@@ -406,6 +418,17 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
        __activate_traps(vcpu);
        __activate_vm(vcpu->kvm);
 
+       /*
+        * If guest last trap to host for handling fpsimd, last_fpsimd_trap
+        * is set. Restore guest's fpsimd state and deactivate fpsimd trap
+        * to avoid guest traping soon.
+        */
+       if (vcpu->last_fpsimd_trap) {
+               __fpsimd_save_state(&host_ctxt->gp_regs.fp_regs);
+               __fpsimd_restore_state(&guest_ctxt->gp_regs.fp_regs);
+               vcpu->last_fpsimd_trap = 0;
+       }
+
        sysreg_restore_guest_state_vhe(guest_ctxt);
        __debug_switch_to_guest(vcpu);
 
@@ -454,6 +477,17 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
        __activate_traps(vcpu);
        __activate_vm(kern_hyp_va(vcpu->kvm));
 
+       /*
+        * If guest last trap to host for handling fpsimd, last_fpsimd_trap
+        * is set. Restore guest's fpsimd state and deactivate fpsimd trap
+        * to avoid guest traping soon.
+        */
+       if (vcpu->last_fpsimd_trap) {
+               __fpsimd_save_state(&host_ctxt->gp_regs.fp_regs);
+               __fpsimd_restore_state(&guest_ctxt->gp_regs.fp_regs);
+               vcpu->last_fpsimd_trap = 0;
+       }
+
        __hyp_vgic_restore_state(vcpu);
        __timer_enable_traps(vcpu);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 
6930c63..46bdf0d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -274,6 +274,7 @@ struct kvm_vcpu {
        bool preempted;
        struct kvm_vcpu_arch arch;
        struct dentry *debugfs_dentry;
+       unsigned int last_fpsimd_trap;
 };
 
 static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
--
2.7.4

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