Re: [PATCH v6 2/6] x86/mce: relocate set{clear}_mce_nospec() functions

[kernel test robot <lkp@intel.com>]

Hi Jane,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on nvdimm/libnvdimm-for-next]
[also build test WARNING on device-mapper-dm/for-next linus/master v5.17-rc8 next-20220318]
[cannot apply to tip/x86/mm]
[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/Jane-Chu/DAX-poison-recovery/20220319-143144
base:   https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git libnvdimm-for-next
config: x86_64-randconfig-a015 (https://download.01.org/0day-ci/archive/20220319/202203191637.PK2oJUeq-lkp@intel.com/config)
compiler: gcc-9 (Ubuntu 9.4.0-1ubuntu1~20.04) 9.4.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/71b9b09529b207ce15667c1f5fba4b727b6754e6
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Jane-Chu/DAX-poison-recovery/20220319-143144
        git checkout 71b9b09529b207ce15667c1f5fba4b727b6754e6
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/mm/pat/ fs/fuse/

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

All warnings (new ones prefixed by >>):

>> arch/x86/mm/pat/set_memory.c:1935:5: warning: no previous prototype for 'set_mce_nospec' [-Wmissing-prototypes]
    1935 | int set_mce_nospec(unsigned long pfn, bool unmap)
         |     ^~~~~~~~~~~~~~
>> arch/x86/mm/pat/set_memory.c:1968:5: warning: no previous prototype for 'clear_mce_nospec' [-Wmissing-prototypes]
    1968 | int clear_mce_nospec(unsigned long pfn)
         |     ^~~~~~~~~~~~~~~~


vim +/set_mce_nospec +1935 arch/x86/mm/pat/set_memory.c

  1927	
  1928	#ifdef CONFIG_X86_64
  1929	/*
  1930	 * Prevent speculative access to the page by either unmapping
  1931	 * it (if we do not require access to any part of the page) or
  1932	 * marking it uncacheable (if we want to try to retrieve data
  1933	 * from non-poisoned lines in the page).
  1934	 */
> 1935	int set_mce_nospec(unsigned long pfn, bool unmap)
  1936	{
  1937		unsigned long decoy_addr;
  1938		int rc;
  1939	
  1940		/* SGX pages are not in the 1:1 map */
  1941		if (arch_is_platform_page(pfn << PAGE_SHIFT))
  1942			return 0;
  1943		/*
  1944		 * We would like to just call:
  1945		 *      set_memory_XX((unsigned long)pfn_to_kaddr(pfn), 1);
  1946		 * but doing that would radically increase the odds of a
  1947		 * speculative access to the poison page because we'd have
  1948		 * the virtual address of the kernel 1:1 mapping sitting
  1949		 * around in registers.
  1950		 * Instead we get tricky.  We create a non-canonical address
  1951		 * that looks just like the one we want, but has bit 63 flipped.
  1952		 * This relies on set_memory_XX() properly sanitizing any __pa()
  1953		 * results with __PHYSICAL_MASK or PTE_PFN_MASK.
  1954		 */
  1955		decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
  1956	
  1957		if (unmap)
  1958			rc = set_memory_np(decoy_addr, 1);
  1959		else
  1960			rc = set_memory_uc(decoy_addr, 1);
  1961		if (rc)
  1962			pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
  1963		return rc;
  1964	}
  1965	EXPORT_SYMBOL(set_mce_nospec);
  1966	
  1967	/* Restore full speculative operation to the pfn. */
> 1968	int clear_mce_nospec(unsigned long pfn)
  1969	{
  1970		return set_memory_wb((unsigned long) pfn_to_kaddr(pfn), 1);
  1971	}
  1972	EXPORT_SYMBOL(clear_mce_nospec);
  1973	

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