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Message-ID: <202001260844.jgEtrb7b%lkp@intel.com>
Date: Sun, 26 Jan 2020 08:39:46 +0800
From: kbuild test robot <lkp@...el.com>
To: linmiaohe <linmiaohe@...wei.com>
Cc: kbuild-all@...ts.01.org, pbonzini@...hat.com, rkrcmar@...hat.com,
sean.j.christopherson@...el.com, vkuznets@...hat.com,
wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
linmiaohe@...wei.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] KVM: x86: avoid some unnecessary copy in
__x86_set_memory_region()
Hi linmiaohe,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on kvm/linux-next]
[also build test WARNING on v5.5-rc7 next-20200124]
[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/linmiaohe/KVM-x86-avoid-some-unnecessary-copy-in-__x86_set_memory_region/20200125-020112
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: i386-allyesconfig (attached as .config)
compiler: gcc-7 (Debian 7.5.0-3) 7.5.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@...el.com>
Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
All warnings (new ones prefixed by >>):
In file included from arch/x86/kvm/x86.c:25:0:
arch/x86/kvm/x86.h: In function 'kvm_dr7_valid':
arch/x86/kvm/x86.h:363:16: warning: right shift count >= width of type [-Wshift-count-overflow]
return !(data >> 32);
^~
arch/x86/kvm/x86.c: In function '__x86_set_memory_region':
>> arch/x86/kvm/x86.c:9730:27: warning: 'npages' may be used uninitialized in this function [-Wmaybe-uninitialized]
vm_munmap(uaddr, npages * PAGE_SIZE);
>> arch/x86/kvm/x86.c:9730:3: warning: 'uaddr' may be used uninitialized in this function [-Wmaybe-uninitialized]
vm_munmap(uaddr, npages * PAGE_SIZE);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vim +/npages +9730 arch/x86/kvm/x86.c
9682
9683 int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size)
9684 {
9685 int i, r;
9686 unsigned long hva, uaddr, npages;
9687 struct kvm_memslots *slots = kvm_memslots(kvm);
9688 struct kvm_memory_slot *slot;
9689
9690 /* Called with kvm->slots_lock held. */
9691 if (WARN_ON(id >= KVM_MEM_SLOTS_NUM))
9692 return -EINVAL;
9693
9694 slot = id_to_memslot(slots, id);
9695 if (size) {
9696 if (slot->npages)
9697 return -EEXIST;
9698
9699 /*
9700 * MAP_SHARED to prevent internal slot pages from being moved
9701 * by fork()/COW.
9702 */
9703 hva = vm_mmap(NULL, 0, size, PROT_READ | PROT_WRITE,
9704 MAP_SHARED | MAP_ANONYMOUS, 0);
9705 if (IS_ERR((void *)hva))
9706 return PTR_ERR((void *)hva);
9707 } else {
9708 if (!slot->npages)
9709 return 0;
9710
9711 hva = 0;
9712 uaddr = slot->userspace_addr;
9713 npages = slot->npages;
9714 }
9715
9716 for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
9717 struct kvm_userspace_memory_region m;
9718
9719 m.slot = id | (i << 16);
9720 m.flags = 0;
9721 m.guest_phys_addr = gpa;
9722 m.userspace_addr = hva;
9723 m.memory_size = size;
9724 r = __kvm_set_memory_region(kvm, &m);
9725 if (r < 0)
9726 return r;
9727 }
9728
9729 if (!size)
> 9730 vm_munmap(uaddr, npages * PAGE_SIZE);
9731
9732 return 0;
9733 }
9734 EXPORT_SYMBOL_GPL(__x86_set_memory_region);
9735
---
0-DAY kernel test infrastructure Open Source Technology Center
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