1:26 a.m.
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-interfac...
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(a)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