KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Peter Xu <peterx@redhat.com>
To: kbuild test robot <lkp@intel.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	kbuild-all@lists.01.org, Vitaly Kuznetsov <vkuznets@redhat.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Christophe de Dinechin <dinechin@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Kevin Tian <kevin.tian@intel.com>
Subject: Re: [PATCH v9 05/14] KVM: X86: Implement ring-based dirty memory tracking
Date: Mon, 25 May 2020 11:26:49 -0400
Message-ID: <20200525152649.GF1058657@xz-x1> (raw)
In-Reply-To: <202005251058.wRNkniwm%lkp@intel.com>

On Mon, May 25, 2020 at 10:48:08AM +0800, kbuild test robot wrote:
> Hi Peter,
> 
> Thank you for the patch! Perhaps something to improve:
> 
> [auto build test WARNING on vhost/linux-next]
> [also build test WARNING on linus/master v5.7-rc7]
> [cannot apply to kvm/linux-next tip/auto-latest linux/master next-20200522]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
> 
> url:    https://github.com/0day-ci/linux/commits/Peter-Xu/KVM-Dirty-ring-interface/20200524-070926
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next
> config: s390-randconfig-s002-20200524 (attached as .config)
> compiler: s390-linux-gcc (GCC) 9.3.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.1-240-gf0fe1cd9-dirty
>         # save the attached .config to linux build tree
>         make W=1 C=1 ARCH=s390 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kbuild test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>, old ones prefixed by <<):
> 
> arch/s390/kvm/../../../virt/kvm/kvm_main.c: In function 'kvm_page_in_dirty_ring':
> >> arch/s390/kvm/../../../virt/kvm/kvm_main.c:2932:16: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
> 2932 |  return (pgoff >= KVM_DIRTY_LOG_PAGE_OFFSET) &&
> |                ^~

Should be a false positive, since when KVM_DIRTY_LOG_PAGE_OFFSET==0 (true for
s390) then the code won't reach here at all due to the previous check [1].

I thought gcc should be able to directly remove the below code when it sees "if
(1) return false;", but it seems not...

I wanted to avoid using "#if" macros because I think it always makes the code
harder to read (especially when nested).  Maybe it's still ok to use one more
time here.

Thanks,

> 
> vim +2932 arch/s390/kvm/../../../virt/kvm/kvm_main.c
> 
>   2926	
>   2927	static bool kvm_page_in_dirty_ring(struct kvm *kvm, unsigned long pgoff)
>   2928	{
>   2929		if (!KVM_DIRTY_LOG_PAGE_OFFSET)
>   2930			return false;

[1]

>   2931	
> > 2932		return (pgoff >= KVM_DIRTY_LOG_PAGE_OFFSET) &&
>   2933		    (pgoff < KVM_DIRTY_LOG_PAGE_OFFSET +
>   2934		     kvm->dirty_ring_size / PAGE_SIZE);
>   2935	}
>   2936	


-- 
Peter Xu


  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-23 22:56 [PATCH v9 00/14] KVM: Dirty ring interface Peter Xu
2020-05-23 22:56 ` [PATCH v9 01/14] KVM: X86: Change parameter for fast_page_fault tracepoint Peter Xu
2020-05-23 22:56 ` [PATCH v9 02/14] KVM: Cache as_id in kvm_memory_slot Peter Xu
2020-05-23 22:56 ` [PATCH v9 03/14] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR] Peter Xu
2020-05-23 22:56 ` [PATCH v9 04/14] KVM: Pass in kvm pointer into mark_page_dirty_in_slot() Peter Xu
2020-05-23 22:56 ` [PATCH v9 05/14] KVM: X86: Implement ring-based dirty memory tracking Peter Xu
2020-05-25  2:48   ` kbuild test robot
2020-05-25 15:26     ` Peter Xu [this message]
     [not found]   ` <202005252245.ZeOB8qNJ%lkp@intel.com>
2020-05-25 15:33     ` Peter Xu
2020-05-23 22:56 ` [PATCH v9 06/14] KVM: Make dirty ring exclusive to dirty bitmap log Peter Xu
2020-05-23 22:56 ` [PATCH v9 07/14] KVM: Don't allocate dirty bitmap if dirty ring is enabled Peter Xu
2020-05-26 15:05   ` kbuild test robot
2020-05-26 15:21     ` Peter Xu
2020-05-27 12:53   ` kbuild test robot
2020-05-23 22:56 ` [PATCH v9 08/14] KVM: selftests: Always clear dirty bitmap after iteration Peter Xu
2020-05-23 22:56 ` [PATCH v9 09/14] KVM: selftests: Sync uapi/linux/kvm.h to tools/ Peter Xu
2020-05-23 22:56 ` [PATCH v9 10/14] KVM: selftests: Use a single binary for dirty/clear log test Peter Xu
2020-05-23 22:56 ` [PATCH v9 11/14] KVM: selftests: Introduce after_vcpu_run hook for dirty " Peter Xu
2020-05-23 22:56 ` [PATCH v9 12/14] KVM: selftests: Add dirty ring buffer test Peter Xu
2020-05-23 23:06 ` [PATCH v9 13/14] KVM: selftests: Let dirty_log_test async for dirty ring test Peter Xu
2020-05-23 23:06 ` [PATCH v9 14/14] KVM: selftests: Add "-c" parameter to dirty log test Peter Xu
2020-05-23 23:14 ` [PATCH v9 00/14] KVM: Dirty ring interface Peter Xu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200525152649.GF1058657@xz-x1 \
    --to=peterx@redhat.com \
    --cc=alex.williamson@redhat.com \
    --cc=dgilbert@redhat.com \
    --cc=dinechin@redhat.com \
    --cc=jasowang@redhat.com \
    --cc=kbuild-all@lists.01.org \
    --cc=kevin.tian@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lkp@intel.com \
    --cc=mst@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=vkuznets@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git