Re: [PATCH] KVM: Optimize kvm_arch_vcpu_ioctl_run function

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On 2020/4/13 16:56, Marc Zyngier wrote:
Tianjia,

On 2020-04-13 04:45, Tianjia Zhang wrote:
kvm_arch_vcpu_ioctl_run() is only called in the file kvm_main.c,
where vcpu->run is the kvm_run parameter, so it has been replaced.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 8 ++++----
 virt/kvm/arm/arm.c | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3bf2ecafd027..70e3f4abbd4d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8726,18 +8726,18 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu
*vcpu, struct kvm_run *kvm_run)
         r = -EAGAIN;
         if (signal_pending(current)) {
             r = -EINTR;
-            vcpu->run->exit_reason = KVM_EXIT_INTR;
+            kvm_run->exit_reason = KVM_EXIT_INTR;
             ++vcpu->stat.signal_exits;
         }
         goto out;
     }

-    if (vcpu->run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
+    if (kvm_run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
         r = -EINVAL;
         goto out;
     }

-    if (vcpu->run->kvm_dirty_regs) {
+    if (kvm_run->kvm_dirty_regs) {
         r = sync_regs(vcpu);
         if (r != 0)
             goto out;
@@ -8767,7 +8767,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu
*vcpu, struct kvm_run *kvm_run)

 out:
     kvm_put_guest_fpu(vcpu);
-    if (vcpu->run->kvm_valid_regs)
+    if (kvm_run->kvm_valid_regs)
         store_regs(vcpu);
     post_kvm_run_save(vcpu);
     kvm_sigset_deactivate(vcpu);
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 48d0ec44ad77..ab9d7966a4c8 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -659,7 +659,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu,
struct kvm_run *run)
         return ret;

     if (run->exit_reason == KVM_EXIT_MMIO) {
-        ret = kvm_handle_mmio_return(vcpu, vcpu->run);
+        ret = kvm_handle_mmio_return(vcpu, run);
         if (ret)
             return ret;
     }

Do you have any number supporting the idea that you are optimizing anything
here? Performance, code size, register pressure or any other relevant metric?

Thanks,

         M.

This is only a simplified implementation of the function, the impact on performance and register pressure can be ignored.

Thanks,
Tianjia
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