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* [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control
@ 2022-05-18 13:45 Uros Bizjak
  2022-05-19  1:04 ` kernel test robot
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Uros Bizjak @ 2022-05-18 13:45 UTC (permalink / raw)
  To: kvm, linux-kernel; +Cc: Uros Bizjak, Paolo Bonzini, Sean Christopherson

Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old
in pi_try_set_control.  cmpxchg returns success in ZF flag, so this
change saves a compare after cmpxchg (and related move instruction
in front of cmpxchg):

  b9:   88 44 24 60             mov    %al,0x60(%rsp)
  bd:   48 89 c8                mov    %rcx,%rax
  c0:   c6 44 24 62 f2          movb   $0xf2,0x62(%rsp)
  c5:   48 8b 74 24 60          mov    0x60(%rsp),%rsi
  ca:   f0 49 0f b1 34 24       lock cmpxchg %rsi,(%r12)
  d0:   48 39 c1                cmp    %rax,%rcx
  d3:   75 cf                   jne    a4 <vmx_vcpu_pi_load+0xa4>

patched:

  c1:   88 54 24 60             mov    %dl,0x60(%rsp)
  c5:   c6 44 24 62 f2          movb   $0xf2,0x62(%rsp)
  ca:   48 8b 54 24 60          mov    0x60(%rsp),%rdx
  cf:   f0 48 0f b1 13          lock cmpxchg %rdx,(%rbx)
  d4:   75 d5                   jne    ab <vmx_vcpu_pi_load+0xab>

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
---
Patch requires commits 0aa7be05d83cc584da0782405e8007e351dfb6cc
and c2df0a6af177b6c06a859806a876f92b072dc624 from tip.git
---
 arch/x86/kvm/vmx/posted_intr.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index 3834bb30ce54..4d41d5994a26 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -34,7 +34,7 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
 	return &(to_vmx(vcpu)->pi_desc);
 }
 
-static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new)
+static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
 {
 	/*
 	 * PID.ON can be set at any time by a different vCPU or by hardware,
@@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new)
 	 * update must be retried with a fresh snapshot an ON change causes
 	 * the cmpxchg to fail.
 	 */
-	if (cmpxchg64(&pi_desc->control, old, new) != old)
+	if (!try_cmpxchg64(&pi_desc->control, pold, new))
 		return -EBUSY;
 
 	return 0;
@@ -111,7 +111,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
 		 * descriptor was modified on "put" to use the wakeup vector.
 		 */
 		new.nv = POSTED_INTR_VECTOR;
-	} while (pi_try_set_control(pi_desc, old.control, new.control));
+	} while (pi_try_set_control(pi_desc, &old.control, new.control));
 
 	local_irq_restore(flags);
 
@@ -161,7 +161,7 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
 
 		/* set 'NV' to 'wakeup vector' */
 		new.nv = POSTED_INTR_WAKEUP_VECTOR;
-	} while (pi_try_set_control(pi_desc, old.control, new.control));
+	} while (pi_try_set_control(pi_desc, &old.control, new.control));
 
 	/*
 	 * Send a wakeup IPI to this CPU if an interrupt may have been posted
-- 
2.35.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control
  2022-05-18 13:45 [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control Uros Bizjak
@ 2022-05-19  1:04 ` kernel test robot
  2022-05-19  6:33     ` Uros Bizjak
  2022-05-19  2:42 ` kernel test robot
  2022-05-19 21:34 ` Uros Bizjak
  2 siblings, 1 reply; 6+ messages in thread
From: kernel test robot @ 2022-05-19  1:04 UTC (permalink / raw)
  To: Uros Bizjak, kvm, linux-kernel
  Cc: kbuild-all, Uros Bizjak, Paolo Bonzini, Sean Christopherson

Hi Uros,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kvm/master]
[also build test ERROR on mst-vhost/linux-next linux/master linus/master v5.18-rc7 next-20220518]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
config: i386-debian-10.3-kselftests (https://download.01.org/0day-ci/archive/20220519/202205190852.VUijQkwc-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
        git checkout 2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kvm/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   arch/x86/kvm/vmx/posted_intr.c: In function 'pi_try_set_control':
>> arch/x86/kvm/vmx/posted_intr.c:45:14: error: implicit declaration of function 'try_cmpxchg64'; did you mean 'try_cmpxchg'? [-Werror=implicit-function-declaration]
      45 |         if (!try_cmpxchg64(&pi_desc->control, pold, new))
         |              ^~~~~~~~~~~~~
         |              try_cmpxchg
   cc1: some warnings being treated as errors


vim +45 arch/x86/kvm/vmx/posted_intr.c

    36	
    37	static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
    38	{
    39		/*
    40		 * PID.ON can be set at any time by a different vCPU or by hardware,
    41		 * e.g. a device.  PID.control must be written atomically, and the
    42		 * update must be retried with a fresh snapshot an ON change causes
    43		 * the cmpxchg to fail.
    44		 */
  > 45		if (!try_cmpxchg64(&pi_desc->control, pold, new))
    46			return -EBUSY;
    47	
    48		return 0;
    49	}
    50	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control
  2022-05-18 13:45 [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control Uros Bizjak
  2022-05-19  1:04 ` kernel test robot
@ 2022-05-19  2:42 ` kernel test robot
  2022-05-19 21:34 ` Uros Bizjak
  2 siblings, 0 replies; 6+ messages in thread
From: kernel test robot @ 2022-05-19  2:42 UTC (permalink / raw)
  To: Uros Bizjak, kvm, linux-kernel
  Cc: llvm, kbuild-all, Uros Bizjak, Paolo Bonzini, Sean Christopherson

Hi Uros,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kvm/master]
[also build test ERROR on mst-vhost/linux-next linux/master linus/master v5.18-rc7 next-20220518]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
config: i386-randconfig-a002 (https://download.01.org/0day-ci/archive/20220519/202205191028.PcCtw7Xz-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 853fa8ee225edf2d0de94b0dcbd31bea916e825e)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
        git checkout 2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kvm/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> arch/x86/kvm/vmx/posted_intr.c:45:7: error: call to undeclared function 'try_cmpxchg64'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           if (!try_cmpxchg64(&pi_desc->control, pold, new))
                ^
   arch/x86/kvm/vmx/posted_intr.c:45:7: note: did you mean '__cmpxchg64'?
   arch/x86/include/asm/cmpxchg_32.h:47:19: note: '__cmpxchg64' declared here
   static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)
                     ^
   1 error generated.


vim +/try_cmpxchg64 +45 arch/x86/kvm/vmx/posted_intr.c

    36	
    37	static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
    38	{
    39		/*
    40		 * PID.ON can be set at any time by a different vCPU or by hardware,
    41		 * e.g. a device.  PID.control must be written atomically, and the
    42		 * update must be retried with a fresh snapshot an ON change causes
    43		 * the cmpxchg to fail.
    44		 */
  > 45		if (!try_cmpxchg64(&pi_desc->control, pold, new))
    46			return -EBUSY;
    47	
    48		return 0;
    49	}
    50	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control
  2022-05-19  1:04 ` kernel test robot
@ 2022-05-19  6:33     ` Uros Bizjak
  0 siblings, 0 replies; 6+ messages in thread
From: Uros Bizjak @ 2022-05-19  6:33 UTC (permalink / raw)
  To: kernel test robot
  Cc: kvm, LKML, kbuild-all, Paolo Bonzini, Sean Christopherson

On Thu, May 19, 2022 at 3:05 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Uros,
>
> Thank you for the patch! Yet something to improve:
>
> [auto build test ERROR on kvm/master]
> [also build test ERROR on mst-vhost/linux-next linux/master linus/master v5.18-rc7 next-20220518]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
> base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
> config: i386-debian-10.3-kselftests (https://download.01.org/0day-ci/archive/20220519/202205190852.VUijQkwc-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
> reproduce (this is a W=1 build):
>         # https://github.com/intel-lab-lkp/linux/commit/2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
>         git checkout 2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kvm/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):

As stated in the patch submission, this patch needs locking
infrastructure patches that are currently in the tip git, so there is
a small patch ordering issue between tip and KVM trees.

Uros.

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control
@ 2022-05-19  6:33     ` Uros Bizjak
  0 siblings, 0 replies; 6+ messages in thread
From: Uros Bizjak @ 2022-05-19  6:33 UTC (permalink / raw)
  To: kbuild-all

[-- Attachment #1: Type: text/plain, Size: 1793 bytes --]

On Thu, May 19, 2022 at 3:05 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Uros,
>
> Thank you for the patch! Yet something to improve:
>
> [auto build test ERROR on kvm/master]
> [also build test ERROR on mst-vhost/linux-next linux/master linus/master v5.18-rc7 next-20220518]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
> base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
> config: i386-debian-10.3-kselftests (https://download.01.org/0day-ci/archive/20220519/202205190852.VUijQkwc-lkp(a)intel.com/config)
> compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
> reproduce (this is a W=1 build):
>         # https://github.com/intel-lab-lkp/linux/commit/2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Uros-Bizjak/KVM-VMX-Use-try_cmpxchg64-in-pi_try_set_control/20220518-214709
>         git checkout 2af4f7c4ecfcaedf9b98ba30ee508dc0d9002955
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kvm/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):

As stated in the patch submission, this patch needs locking
infrastructure patches that are currently in the tip git, so there is
a small patch ordering issue between tip and KVM trees.

Uros.

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control
  2022-05-18 13:45 [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control Uros Bizjak
  2022-05-19  1:04 ` kernel test robot
  2022-05-19  2:42 ` kernel test robot
@ 2022-05-19 21:34 ` Uros Bizjak
  2 siblings, 0 replies; 6+ messages in thread
From: Uros Bizjak @ 2022-05-19 21:34 UTC (permalink / raw)
  To: kvm, LKML; +Cc: Paolo Bonzini, Sean Christopherson

On Wed, May 18, 2022 at 3:46 PM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old
> in pi_try_set_control.  cmpxchg returns success in ZF flag, so this
> change saves a compare after cmpxchg (and related move instruction
> in front of cmpxchg):
>
>   b9:   88 44 24 60             mov    %al,0x60(%rsp)
>   bd:   48 89 c8                mov    %rcx,%rax
>   c0:   c6 44 24 62 f2          movb   $0xf2,0x62(%rsp)
>   c5:   48 8b 74 24 60          mov    0x60(%rsp),%rsi
>   ca:   f0 49 0f b1 34 24       lock cmpxchg %rsi,(%r12)
>   d0:   48 39 c1                cmp    %rax,%rcx
>   d3:   75 cf                   jne    a4 <vmx_vcpu_pi_load+0xa4>
>
> patched:
>
>   c1:   88 54 24 60             mov    %dl,0x60(%rsp)
>   c5:   c6 44 24 62 f2          movb   $0xf2,0x62(%rsp)
>   ca:   48 8b 54 24 60          mov    0x60(%rsp),%rdx
>   cf:   f0 48 0f b1 13          lock cmpxchg %rdx,(%rbx)
>   d4:   75 d5                   jne    ab <vmx_vcpu_pi_load+0xab>
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> ---
> Patch requires commits 0aa7be05d83cc584da0782405e8007e351dfb6cc
> and c2df0a6af177b6c06a859806a876f92b072dc624 from tip.git
> ---
>  arch/x86/kvm/vmx/posted_intr.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> index 3834bb30ce54..4d41d5994a26 100644
> --- a/arch/x86/kvm/vmx/posted_intr.c
> +++ b/arch/x86/kvm/vmx/posted_intr.c
> @@ -34,7 +34,7 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
>         return &(to_vmx(vcpu)->pi_desc);
>  }
>
> -static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new)
> +static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
>  {
>         /*
>          * PID.ON can be set at any time by a different vCPU or by hardware,
> @@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new)
>          * update must be retried with a fresh snapshot an ON change causes
>          * the cmpxchg to fail.
>          */
> -       if (cmpxchg64(&pi_desc->control, old, new) != old)
> +       if (!try_cmpxchg64(&pi_desc->control, pold, new))

Actually, we can just use the address of local variable &old here, no
need to change function arguments.

Patch v2 incoming...

Uros.

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-05-19 21:34 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-05-18 13:45 [PATCH] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control Uros Bizjak
2022-05-19  1:04 ` kernel test robot
2022-05-19  6:33   ` Uros Bizjak
2022-05-19  6:33     ` Uros Bizjak
2022-05-19  2:42 ` kernel test robot
2022-05-19 21:34 ` Uros Bizjak

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