Re: [PATCH v2] KVM: Optimize kvm_arch_vcpu_ioctl_run function

[Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>]

On 2020/4/16 16:28, Marc Zyngier wrote:
> On 2020-04-16 08:03, Vitaly Kuznetsov wrote:
> > Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
> > > ---
> > >
> > > 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.
>
> Something like this (untested):
>
> diff --git a/arch/arm64/include/asm/kvm_host.h 
> b/arch/arm64/include/asm/kvm_host.h
> index 32c8a675e5a4..82978995bdd6 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -490,7 +490,7 @@ void handle_exit_early(struct kvm_vcpu *vcpu, struct 
> kvm_run *run,
>   void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data);
>   unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len);
>
> -int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
> +int kvm_handle_mmio_return(struct kvm_vcpu *vcpu);
>   int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
>            phys_addr_t fault_ipa);
>
> diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c
> index 4e0366759726..3b2c822b4859 100644
> --- a/virt/kvm/arm/mmio.c
> +++ b/virt/kvm/arm/mmio.c
> @@ -77,9 +77,8 @@ unsigned long kvm_mmio_read_buf(const void *buf, 
> unsigned int len)
>    *                 or in-kernel IO emulation
>    *
>    * @vcpu: The VCPU pointer
> - * @run:  The VCPU run struct containing the mmio data
>    */
> -int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
>   {
>       unsigned long data;
>       unsigned int len;
> @@ -93,7 +92,7 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, 
> struct kvm_run *run)
>
>       if (!kvm_vcpu_dabt_iswrite(vcpu)) {
>           len = kvm_vcpu_dabt_get_as(vcpu);
> -        data = kvm_mmio_read_buf(run->mmio.data, len);
> +        data = kvm_mmio_read_buf(vcpu->run->mmio.data, len);
>
>           if (kvm_vcpu_dabt_issext(vcpu) &&
>               len < sizeof(unsigned long)) {
> @@ -104,7 +103,8 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, 
> struct kvm_run *run)
>           if (!kvm_vcpu_dabt_issf(vcpu))
>               data = data & 0xffffffff;
>
> -        trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
> +        trace_kvm_mmio(KVM_TRACE_MMIO_READ, len,
> +                   vcpu->run->mmio.phys_addr,
>                      &data);
>           data = vcpu_data_host_to_guest(vcpu, data, len);
>           vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data);
>
> Overall, there is a large set of cleanups to be done when both the vcpu 
> and the run
> structures are passed as parameters at the same time. Just grepping the 
> tree for
> kvm_run is pretty instructive.
>
>          M.

Sorry, it's my mistake, I only compiled the x86 platform, I will submit 
patch again.

Thanks,
Tianjia