[v7,17/17] mm: add mmu_notifier argument to follow_pfn
diff mbox series

Message ID 20201127164131.2244124-18-daniel.vetter@ffwll.ch
State New, archived
Headers show
Series
  • follow_pfn and other iomap races
Related show

Commit Message

Daniel Vetter Nov. 27, 2020, 4:41 p.m. UTC
The only safe way for non core/arch code to use follow_pfn() is
together with an mmu_notifier subscription. follow_pfn() is already
marked as _GPL and the kerneldoc explains this restriction.

This patch here enforces all this by adding a mmu_notifier argument
and verifying that it is registered for the correct mm_struct.

Motivated by discussions with Christoph Hellwig and Jason Gunthorpe.

Since requiring an mmu_notifier makes it very clear that follow_pfn()
cannot be used on !CONFIG_MMU hardware, remove it from there. The sole
user kvm not existing on such hardware also supports that.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Cc: kvm@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
--
v7: Comments from Jason:
- ditch follow_pfn from nommu.c
- simplify mmu_notifer->mm check
---
 include/linux/mm.h  |  3 ++-
 mm/memory.c         | 38 ++++++++++++++++++++++++--------------
 mm/nommu.c          | 27 +++++----------------------
 virt/kvm/kvm_main.c |  4 ++--
 4 files changed, 33 insertions(+), 39 deletions(-)

Comments

kernel test robot Nov. 27, 2020, 7:10 p.m. UTC | #1
Hi Daniel,

I love your patch! Yet something to improve:

[auto build test ERROR on linuxtv-media/master]
[also build test ERROR on char-misc/char-misc-testing v5.10-rc5]
[cannot apply to hnaz-linux-mm/master next-20201127]
[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/0day-ci/linux/commits/Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421
base:   git://linuxtv.org/media_tree.git master
config: s390-randconfig-r032-20201127 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project f095ac11a9550530a4a54298debb8b04b36422be)
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
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # https://github.com/0day-ci/linux/commit/d76a3489433ce67d45da86aa12953385427f0ac9
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421
        git checkout d76a3489433ce67d45da86aa12953385427f0ac9
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390 

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 >>):

   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:80:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32'
           ___constant_swab32(x) :                 \
                              ^
   include/uapi/linux/swab.h:21:12: note: expanded from macro '___constant_swab32'
           (((__u32)(x) & (__u32)0x00ff0000UL) >>  8) |            \
                     ^
   In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
   In file included from include/linux/kvm_host.h:32:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:36:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:80:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32'
           ___constant_swab32(x) :                 \
                              ^
   include/uapi/linux/swab.h:22:12: note: expanded from macro '___constant_swab32'
           (((__u32)(x) & (__u32)0xff000000UL) >> 24)))
                     ^
   In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
   In file included from include/linux/kvm_host.h:32:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:36:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:80:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:120:12: note: expanded from macro '__swab32'
           __fswab32(x))
                     ^
   In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
   In file included from include/linux/kvm_host.h:32:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:36:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:80:
   include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsb(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsw(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsl(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesb(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesw(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesl(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
>> arch/s390/kvm/../../../virt/kvm/kvm_main.c:1894:40: error: no member named 'mmu_notifier' in 'struct kvm'
           r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
                                            ~~~  ^
   arch/s390/kvm/../../../virt/kvm/kvm_main.c:1909:41: error: no member named 'mmu_notifier' in 'struct kvm'
                   r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
                                                    ~~~  ^
   20 warnings and 2 errors generated.

vim +1894 arch/s390/kvm/../../../virt/kvm/kvm_main.c

  1885	
  1886	static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
  1887				       unsigned long addr, bool *async,
  1888				       bool write_fault, bool *writable,
  1889				       kvm_pfn_t *p_pfn)
  1890	{
  1891		unsigned long pfn;
  1892		int r;
  1893	
> 1894		r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
  1895		if (r) {
  1896			/*
  1897			 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
  1898			 * not call the fault handler, so do it here.
  1899			 */
  1900			bool unlocked = false;
  1901			r = fixup_user_fault(current->mm, addr,
  1902					     (write_fault ? FAULT_FLAG_WRITE : 0),
  1903					     &unlocked);
  1904			if (unlocked)
  1905				return -EAGAIN;
  1906			if (r)
  1907				return r;
  1908	
  1909			r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
  1910			if (r)
  1911				return r;
  1912	
  1913		}
  1914	
  1915		if (writable)
  1916			*writable = true;
  1917	
  1918		/*
  1919		 * Get a reference here because callers of *hva_to_pfn* and
  1920		 * *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
  1921		 * returned pfn.  This is only needed if the VMA has VM_MIXEDMAP
  1922		 * set, but the kvm_get_pfn/kvm_release_pfn_clean pair will
  1923		 * simply do nothing for reserved pfns.
  1924		 *
  1925		 * Whoever called remap_pfn_range is also going to call e.g.
  1926		 * unmap_mapping_range before the underlying pages are freed,
  1927		 * causing a call to our MMU notifier.
  1928		 */ 
  1929		kvm_get_pfn(pfn);
  1930	
  1931		*p_pfn = pfn;
  1932		return 0;
  1933	}
  1934	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Daniel Vetter Nov. 30, 2020, 2:28 p.m. UTC | #2
So I guess kvm platforms that don't set KVM_ARCH_WANT_MMU_NOTIFIER exist,
and at least on powerpc they're consistent with KVM_CAP_SYNC_MMU
signalling that the guest pagetables stays in sync automatically with any
updates. So for that case I guess we could use unsafe_follow_pfn.

But on s390 this seems different: No mmu notifier, but KVM_CAP_SYNC_MMU is
set. So I guess there's some hardware magic on s390 that I don't know
about.

Not sure what to do with this now here ...
-Daniel


On Sat, Nov 28, 2020 at 03:10:40AM +0800, kernel test robot wrote:
> Hi Daniel,
> 
> I love your patch! Yet something to improve:
> 
> [auto build test ERROR on linuxtv-media/master]
> [also build test ERROR on char-misc/char-misc-testing v5.10-rc5]
> [cannot apply to hnaz-linux-mm/master next-20201127]
> [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/0day-ci/linux/commits/Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421
> base:   git://linuxtv.org/media_tree.git master
> config: s390-randconfig-r032-20201127 (attached as .config)
> compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project f095ac11a9550530a4a54298debb8b04b36422be)
> 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
>         # install s390 cross compiling tool for clang build
>         # apt-get install binutils-s390x-linux-gnu
>         # https://github.com/0day-ci/linux/commit/d76a3489433ce67d45da86aa12953385427f0ac9
>         git remote add linux-review https://github.com/0day-ci/linux
>         git fetch --no-tags linux-review Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421
>         git checkout d76a3489433ce67d45da86aa12953385427f0ac9
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390 
> 
> 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 >>):
> 
>    In file included from arch/s390/include/asm/kvm_para.h:25:
>    In file included from arch/s390/include/asm/diag.h:12:
>    In file included from include/linux/if_ether.h:19:
>    In file included from include/linux/skbuff.h:31:
>    In file included from include/linux/dma-mapping.h:10:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:80:
>    include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
>                                                            ~~~~~~~~~~ ^
>    include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
>    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
>                                                              ^
>    include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32'
>            ___constant_swab32(x) :                 \
>                               ^
>    include/uapi/linux/swab.h:21:12: note: expanded from macro '___constant_swab32'
>            (((__u32)(x) & (__u32)0x00ff0000UL) >>  8) |            \
>                      ^
>    In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
>    In file included from include/linux/kvm_host.h:32:
>    In file included from include/linux/kvm_para.h:5:
>    In file included from include/uapi/linux/kvm_para.h:36:
>    In file included from arch/s390/include/asm/kvm_para.h:25:
>    In file included from arch/s390/include/asm/diag.h:12:
>    In file included from include/linux/if_ether.h:19:
>    In file included from include/linux/skbuff.h:31:
>    In file included from include/linux/dma-mapping.h:10:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:80:
>    include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
>                                                            ~~~~~~~~~~ ^
>    include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
>    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
>                                                              ^
>    include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32'
>            ___constant_swab32(x) :                 \
>                               ^
>    include/uapi/linux/swab.h:22:12: note: expanded from macro '___constant_swab32'
>            (((__u32)(x) & (__u32)0xff000000UL) >> 24)))
>                      ^
>    In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
>    In file included from include/linux/kvm_host.h:32:
>    In file included from include/linux/kvm_para.h:5:
>    In file included from include/uapi/linux/kvm_para.h:36:
>    In file included from arch/s390/include/asm/kvm_para.h:25:
>    In file included from arch/s390/include/asm/diag.h:12:
>    In file included from include/linux/if_ether.h:19:
>    In file included from include/linux/skbuff.h:31:
>    In file included from include/linux/dma-mapping.h:10:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:80:
>    include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
>                                                            ~~~~~~~~~~ ^
>    include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
>    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
>                                                              ^
>    include/uapi/linux/swab.h:120:12: note: expanded from macro '__swab32'
>            __fswab32(x))
>                      ^
>    In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
>    In file included from include/linux/kvm_host.h:32:
>    In file included from include/linux/kvm_para.h:5:
>    In file included from include/uapi/linux/kvm_para.h:36:
>    In file included from arch/s390/include/asm/kvm_para.h:25:
>    In file included from arch/s390/include/asm/diag.h:12:
>    In file included from include/linux/if_ether.h:19:
>    In file included from include/linux/skbuff.h:31:
>    In file included from include/linux/dma-mapping.h:10:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:80:
>    include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            __raw_writeb(value, PCI_IOBASE + addr);
>                                ~~~~~~~~~~ ^
>    include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
>                                                          ~~~~~~~~~~ ^
>    include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
>                                                          ~~~~~~~~~~ ^
>    include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            readsb(PCI_IOBASE + addr, buffer, count);
>                   ~~~~~~~~~~ ^
>    include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            readsw(PCI_IOBASE + addr, buffer, count);
>                   ~~~~~~~~~~ ^
>    include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            readsl(PCI_IOBASE + addr, buffer, count);
>                   ~~~~~~~~~~ ^
>    include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            writesb(PCI_IOBASE + addr, buffer, count);
>                    ~~~~~~~~~~ ^
>    include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            writesw(PCI_IOBASE + addr, buffer, count);
>                    ~~~~~~~~~~ ^
>    include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            writesl(PCI_IOBASE + addr, buffer, count);
>                    ~~~~~~~~~~ ^
> >> arch/s390/kvm/../../../virt/kvm/kvm_main.c:1894:40: error: no member named 'mmu_notifier' in 'struct kvm'
>            r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
>                                             ~~~  ^
>    arch/s390/kvm/../../../virt/kvm/kvm_main.c:1909:41: error: no member named 'mmu_notifier' in 'struct kvm'
>                    r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
>                                                     ~~~  ^
>    20 warnings and 2 errors generated.
> 
> vim +1894 arch/s390/kvm/../../../virt/kvm/kvm_main.c
> 
>   1885	
>   1886	static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
>   1887				       unsigned long addr, bool *async,
>   1888				       bool write_fault, bool *writable,
>   1889				       kvm_pfn_t *p_pfn)
>   1890	{
>   1891		unsigned long pfn;
>   1892		int r;
>   1893	
> > 1894		r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
>   1895		if (r) {
>   1896			/*
>   1897			 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
>   1898			 * not call the fault handler, so do it here.
>   1899			 */
>   1900			bool unlocked = false;
>   1901			r = fixup_user_fault(current->mm, addr,
>   1902					     (write_fault ? FAULT_FLAG_WRITE : 0),
>   1903					     &unlocked);
>   1904			if (unlocked)
>   1905				return -EAGAIN;
>   1906			if (r)
>   1907				return r;
>   1908	
>   1909			r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
>   1910			if (r)
>   1911				return r;
>   1912	
>   1913		}
>   1914	
>   1915		if (writable)
>   1916			*writable = true;
>   1917	
>   1918		/*
>   1919		 * Get a reference here because callers of *hva_to_pfn* and
>   1920		 * *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
>   1921		 * returned pfn.  This is only needed if the VMA has VM_MIXEDMAP
>   1922		 * set, but the kvm_get_pfn/kvm_release_pfn_clean pair will
>   1923		 * simply do nothing for reserved pfns.
>   1924		 *
>   1925		 * Whoever called remap_pfn_range is also going to call e.g.
>   1926		 * unmap_mapping_range before the underlying pages are freed,
>   1927		 * causing a call to our MMU notifier.
>   1928		 */ 
>   1929		kvm_get_pfn(pfn);
>   1930	
>   1931		*p_pfn = pfn;
>   1932		return 0;
>   1933	}
>   1934	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Nick Desaulniers Nov. 30, 2020, 6:03 p.m. UTC | #3
On Mon, Nov 30, 2020 at 6:28 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> So I guess kvm platforms that don't set KVM_ARCH_WANT_MMU_NOTIFIER exist,
> and at least on powerpc they're consistent with KVM_CAP_SYNC_MMU
> signalling that the guest pagetables stays in sync automatically with any
> updates. So for that case I guess we could use unsafe_follow_pfn.
>
> But on s390 this seems different: No mmu notifier, but KVM_CAP_SYNC_MMU is
> set. So I guess there's some hardware magic on s390 that I don't know
> about.

+ Vasily + Heiko +s390

>
> Not sure what to do with this now here ...
> -Daniel
>
>
> On Sat, Nov 28, 2020 at 03:10:40AM +0800, kernel test robot wrote:
> > Hi Daniel,
> >
> > I love your patch! Yet something to improve:
> >
> > [auto build test ERROR on linuxtv-media/master]
> > [also build test ERROR on char-misc/char-misc-testing v5.10-rc5]
> > [cannot apply to hnaz-linux-mm/master next-20201127]
> > [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/0day-ci/linux/commits/Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421
> > base:   git://linuxtv.org/media_tree.git master
> > config: s390-randconfig-r032-20201127 (attached as .config)
> > compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project f095ac11a9550530a4a54298debb8b04b36422be)
> > 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
> >         # install s390 cross compiling tool for clang build
> >         # apt-get install binutils-s390x-linux-gnu
> >         # https://github.com/0day-ci/linux/commit/d76a3489433ce67d45da86aa12953385427f0ac9
> >         git remote add linux-review https://github.com/0day-ci/linux
> >         git fetch --no-tags linux-review Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421
> >         git checkout d76a3489433ce67d45da86aa12953385427f0ac9
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390
> >
> > 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 >>):
> >
> >    In file included from arch/s390/include/asm/kvm_para.h:25:
> >    In file included from arch/s390/include/asm/diag.h:12:
> >    In file included from include/linux/if_ether.h:19:
> >    In file included from include/linux/skbuff.h:31:
> >    In file included from include/linux/dma-mapping.h:10:
> >    In file included from include/linux/scatterlist.h:9:
> >    In file included from arch/s390/include/asm/io.h:80:
> >    include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
> >                                                            ~~~~~~~~~~ ^
> >    include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
> >    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
> >                                                              ^
> >    include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32'
> >            ___constant_swab32(x) :                 \
> >                               ^
> >    include/uapi/linux/swab.h:21:12: note: expanded from macro '___constant_swab32'
> >            (((__u32)(x) & (__u32)0x00ff0000UL) >>  8) |            \
> >                      ^
> >    In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
> >    In file included from include/linux/kvm_host.h:32:
> >    In file included from include/linux/kvm_para.h:5:
> >    In file included from include/uapi/linux/kvm_para.h:36:
> >    In file included from arch/s390/include/asm/kvm_para.h:25:
> >    In file included from arch/s390/include/asm/diag.h:12:
> >    In file included from include/linux/if_ether.h:19:
> >    In file included from include/linux/skbuff.h:31:
> >    In file included from include/linux/dma-mapping.h:10:
> >    In file included from include/linux/scatterlist.h:9:
> >    In file included from arch/s390/include/asm/io.h:80:
> >    include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
> >                                                            ~~~~~~~~~~ ^
> >    include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
> >    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
> >                                                              ^
> >    include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32'
> >            ___constant_swab32(x) :                 \
> >                               ^
> >    include/uapi/linux/swab.h:22:12: note: expanded from macro '___constant_swab32'
> >            (((__u32)(x) & (__u32)0xff000000UL) >> 24)))
> >                      ^
> >    In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
> >    In file included from include/linux/kvm_host.h:32:
> >    In file included from include/linux/kvm_para.h:5:
> >    In file included from include/uapi/linux/kvm_para.h:36:
> >    In file included from arch/s390/include/asm/kvm_para.h:25:
> >    In file included from arch/s390/include/asm/diag.h:12:
> >    In file included from include/linux/if_ether.h:19:
> >    In file included from include/linux/skbuff.h:31:
> >    In file included from include/linux/dma-mapping.h:10:
> >    In file included from include/linux/scatterlist.h:9:
> >    In file included from arch/s390/include/asm/io.h:80:
> >    include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
> >                                                            ~~~~~~~~~~ ^
> >    include/uapi/linux/byteorder/big_endian.h:34:59: note: expanded from macro '__le32_to_cpu'
> >    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
> >                                                              ^
> >    include/uapi/linux/swab.h:120:12: note: expanded from macro '__swab32'
> >            __fswab32(x))
> >                      ^
> >    In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18:
> >    In file included from include/linux/kvm_host.h:32:
> >    In file included from include/linux/kvm_para.h:5:
> >    In file included from include/uapi/linux/kvm_para.h:36:
> >    In file included from arch/s390/include/asm/kvm_para.h:25:
> >    In file included from arch/s390/include/asm/diag.h:12:
> >    In file included from include/linux/if_ether.h:19:
> >    In file included from include/linux/skbuff.h:31:
> >    In file included from include/linux/dma-mapping.h:10:
> >    In file included from include/linux/scatterlist.h:9:
> >    In file included from arch/s390/include/asm/io.h:80:
> >    include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            __raw_writeb(value, PCI_IOBASE + addr);
> >                                ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
> >                                                          ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
> >                                                          ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            readsb(PCI_IOBASE + addr, buffer, count);
> >                   ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            readsw(PCI_IOBASE + addr, buffer, count);
> >                   ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            readsl(PCI_IOBASE + addr, buffer, count);
> >                   ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            writesb(PCI_IOBASE + addr, buffer, count);
> >                    ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            writesw(PCI_IOBASE + addr, buffer, count);
> >                    ~~~~~~~~~~ ^
> >    include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            writesl(PCI_IOBASE + addr, buffer, count);
> >                    ~~~~~~~~~~ ^
> > >> arch/s390/kvm/../../../virt/kvm/kvm_main.c:1894:40: error: no member named 'mmu_notifier' in 'struct kvm'
> >            r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
> >                                             ~~~  ^
> >    arch/s390/kvm/../../../virt/kvm/kvm_main.c:1909:41: error: no member named 'mmu_notifier' in 'struct kvm'
> >                    r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
> >                                                     ~~~  ^
> >    20 warnings and 2 errors generated.
> >
> > vim +1894 arch/s390/kvm/../../../virt/kvm/kvm_main.c
> >
> >   1885
> >   1886        static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
> >   1887                                       unsigned long addr, bool *async,
> >   1888                                       bool write_fault, bool *writable,
> >   1889                                       kvm_pfn_t *p_pfn)
> >   1890        {
> >   1891                unsigned long pfn;
> >   1892                int r;
> >   1893
> > > 1894                r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
> >   1895                if (r) {
> >   1896                        /*
> >   1897                         * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
> >   1898                         * not call the fault handler, so do it here.
> >   1899                         */
> >   1900                        bool unlocked = false;
> >   1901                        r = fixup_user_fault(current->mm, addr,
> >   1902                                             (write_fault ? FAULT_FLAG_WRITE : 0),
> >   1903                                             &unlocked);
> >   1904                        if (unlocked)
> >   1905                                return -EAGAIN;
> >   1906                        if (r)
> >   1907                                return r;
> >   1908
> >   1909                        r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
> >   1910                        if (r)
> >   1911                                return r;
> >   1912
> >   1913                }
> >   1914
> >   1915                if (writable)
> >   1916                        *writable = true;
> >   1917
> >   1918                /*
> >   1919                 * Get a reference here because callers of *hva_to_pfn* and
> >   1920                 * *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
> >   1921                 * returned pfn.  This is only needed if the VMA has VM_MIXEDMAP
> >   1922                 * set, but the kvm_get_pfn/kvm_release_pfn_clean pair will
> >   1923                 * simply do nothing for reserved pfns.
> >   1924                 *
> >   1925                 * Whoever called remap_pfn_range is also going to call e.g.
> >   1926                 * unmap_mapping_range before the underlying pages are freed,
> >   1927                 * causing a call to our MMU notifier.
> >   1928                 */
> >   1929                kvm_get_pfn(pfn);
> >   1930
> >   1931                *p_pfn = pfn;
> >   1932                return 0;
> >   1933        }
> >   1934
> >
> > ---
> > 0-DAY CI Kernel Test Service, Intel Corporation
> > https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20201130142820.GN401619%40phenom.ffwll.local.

Patch
diff mbox series

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bb3e926afd91..2a564bfd818c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1651,6 +1651,7 @@  void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long start, unsigned long end);
 
 struct mmu_notifier_range;
+struct mmu_notifier;
 
 void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
 		unsigned long end, unsigned long floor, unsigned long ceiling);
@@ -1660,7 +1661,7 @@  int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 		   struct mmu_notifier_range *range,
 		   pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
-	unsigned long *pfn);
+	unsigned long *pfn, struct mmu_notifier *subscription);
 int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
 		      unsigned long *pfn);
 int follow_phys(struct vm_area_struct *vma, unsigned long address,
diff --git a/mm/memory.c b/mm/memory.c
index 0db0c5e233fd..a27b9b9c22c2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4789,11 +4789,30 @@  int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 }
 EXPORT_SYMBOL(follow_pte_pmd);
 
+static int __follow_pfn(struct vm_area_struct *vma, unsigned long address,
+			unsigned long *pfn)
+{
+	int ret = -EINVAL;
+	spinlock_t *ptl;
+	pte_t *ptep;
+
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		return ret;
+
+	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
+	if (ret)
+		return ret;
+	*pfn = pte_pfn(*ptep);
+	pte_unmap_unlock(ptep, ptl);
+	return 0;
+}
+
 /**
  * follow_pfn - look up PFN at a user virtual address
  * @vma: memory mapping
  * @address: user virtual address
  * @pfn: location to store found PFN
+ * @subscription: mmu_notifier subscription for the mm @vma is part of
  *
  * Only IO mappings and raw PFN mappings are allowed. Note that callers must
  * ensure coherency with pte updates by using a &mmu_notifier to follow updates.
@@ -4805,21 +4824,12 @@  EXPORT_SYMBOL(follow_pte_pmd);
  * Return: zero and the pfn at @pfn on success, -ve otherwise.
  */
 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
-	unsigned long *pfn)
+	unsigned long *pfn, struct mmu_notifier *subscription)
 {
-	int ret = -EINVAL;
-	spinlock_t *ptl;
-	pte_t *ptep;
-
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
-		return ret;
+	if (WARN_ON(subscription->mm != vma->vm_mm))
+		return -EINVAL;
 
-	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
-	if (ret)
-		return ret;
-	*pfn = pte_pfn(*ptep);
-	pte_unmap_unlock(ptep, ptl);
-	return 0;
+	return __follow_pfn(vma, address, pfn);
 }
 EXPORT_SYMBOL_GPL(follow_pfn);
 
@@ -4844,7 +4854,7 @@  int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
 	WARN_ONCE(1, "unsafe follow_pfn usage\n");
 	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
 
-	return follow_pfn(vma, address, pfn);
+	return __follow_pfn(vma, address, pfn);
 }
 EXPORT_SYMBOL(unsafe_follow_pfn);
 
diff --git a/mm/nommu.c b/mm/nommu.c
index 79fc98a6c94a..a1e178401146 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -111,27 +111,6 @@  unsigned int kobjsize(const void *objp)
 	return page_size(page);
 }
 
-/**
- * follow_pfn - look up PFN at a user virtual address
- * @vma: memory mapping
- * @address: user virtual address
- * @pfn: location to store found PFN
- *
- * Only IO mappings and raw PFN mappings are allowed.
- *
- * Returns zero and the pfn at @pfn on success, -ve otherwise.
- */
-int follow_pfn(struct vm_area_struct *vma, unsigned long address,
-	unsigned long *pfn)
-{
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
-		return -EINVAL;
-
-	*pfn = address >> PAGE_SHIFT;
-	return 0;
-}
-EXPORT_SYMBOL_GPL(follow_pfn);
-
 /**
  * unsafe_follow_pfn - look up PFN at a user virtual address
  * @vma: memory mapping
@@ -153,7 +132,11 @@  int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
 	WARN_ONCE(1, "unsafe follow_pfn usage\n");
 	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
 
-	return follow_pfn(vma, address, pfn);
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		return -EINVAL;
+
+	*pfn = address >> PAGE_SHIFT;
+	return 0;
 }
 EXPORT_SYMBOL(unsafe_follow_pfn);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 417f3d470c3e..6f6786524eff 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1891,7 +1891,7 @@  static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
 	unsigned long pfn;
 	int r;
 
-	r = follow_pfn(vma, addr, &pfn);
+	r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
 	if (r) {
 		/*
 		 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
@@ -1906,7 +1906,7 @@  static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
 		if (r)
 			return r;
 
-		r = follow_pfn(vma, addr, &pfn);
+		r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
 		if (r)
 			return r;