Re: [PATCH v2] KVM: Optimize kvm_arch_vcpu_ioctl_run function

Vitaly Kuznetsov
2020-04-16T07:03:56Z

Tianjia Zhang <tianjia.zhang@linux.alibaba.com> writes:

> In earlier versions of kvm, 'kvm_run' is an independent structure
> and is not included in the vcpu structure. At present, 'kvm_run'
> is already included in the vcpu structure, so the parameter
> 'kvm_run' is redundant.
>
> This patch simplify the function definition, removes the extra
> 'kvm_run' parameter, and extract it from the 'kvm_vcpu' structure
> if necessary.
>
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> ---
>
> v2 change:
> remove 'kvm_run' parameter and extract it from 'kvm_vcpu'
>
> arch/mips/kvm/mips.c | 3 ++-
> arch/powerpc/kvm/powerpc.c | 3 ++-
> arch/s390/kvm/kvm-s390.c | 3 ++-
> arch/x86/kvm/x86.c | 11 ++++++-----
> include/linux/kvm_host.h | 2 +-
> virt/kvm/arm/arm.c | 6 +++---
> virt/kvm/kvm_main.c | 2 +-
> 7 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 8f05dd0a0f4e..ec24adf4857e 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -439,8 +439,9 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> return -ENOIOCTLCMD;
> }
>
> -int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> {
> + struct kvm_run *run = vcpu->run;
> int r = -EINTR;
>
> vcpu_load(vcpu);
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index e15166b0a16d..7e24691e138a 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -1764,8 +1764,9 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
> return r;
> }
>
> -int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> {
> + struct kvm_run *run = vcpu->run;
> int r;
>
> vcpu_load(vcpu);
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 19a81024fe16..443af3ead739 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4333,8 +4333,9 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> store_regs_fmt2(vcpu, kvm_run);
> }
>
> -int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> {
> + struct kvm_run *kvm_run = vcpu->run;
> int rc;
>
> if (kvm_run->immediate_exit)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3bf2ecafd027..a0338e86c90f 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8707,8 +8707,9 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
> trace_kvm_fpu(0);
> }
>
> -int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> {
> + struct kvm_run *kvm_run = vcpu->run;
> int r;
>
> vcpu_load(vcpu);
> @@ -8726,18 +8727,18 @@ 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 +8768,7 @@ 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/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 6d58beb65454..1e17ef719595 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -866,7 +866,7 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
> struct kvm_mp_state *mp_state);
> int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> struct kvm_guest_debug *dbg);
> -int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run);
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu);
>
> int kvm_arch_init(void *opaque);
> void kvm_arch_exit(void);
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 48d0ec44ad77..f5390ac2165b 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -639,7 +639,6 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
> /**
> * kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
> * @vcpu: The VCPU pointer
> - * @run: The kvm_run structure pointer used for userspace state exchange
> *
> * This function is called through the VCPU_RUN ioctl called from user space. It
> * will execute VM code in a loop until the time slice for the process is used
> @@ -647,8 +646,9 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
> * return with return value 0 and with the kvm_run structure filled in with the
> * required data for the requested emulation.
> */
> -int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> {
> + struct kvm_run *run = vcpu->run;
> int ret;
>
> if (unlikely(!kvm_vcpu_initialized(vcpu)))
> @@ -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);

I don't know much about ARM but this also seems redundant,
kvm_handle_mmio_return() is also able to extruct 'struct kvm_run' from'
'struct kvm_vcpu'. This likely deserves it's own patch though.

> if (ret)
> return ret;
> }
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 74bdb7bf3295..e18faea89146 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3135,7 +3135,7 @@ static long kvm_vcpu_ioctl(struct file *filp,
> synchronize_rcu();
> put_pid(oldpid);
> }
> - r = kvm_arch_vcpu_ioctl_run(vcpu, vcpu->run);
> + r = kvm_arch_vcpu_ioctl_run(vcpu);
> trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
> break;
> }

Looked at non-x86 arches just briefly but there seems to be no
controversy here, so

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly