Re: [PATCH 18/18] KVM: arm64: Plumb the pKVM MMU in KVM

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

Hi Quentin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on v6.12-rc6]
[also build test WARNING on linus/master]
[cannot apply to kvmarm/next next-20241104]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Quentin-Perret/KVM-arm64-Change-the-layout-of-enum-pkvm_page_state/20241104-213817
base:   v6.12-rc6
patch link:    https://lore.kernel.org/r/20241104133204.85208-19-qperret%40google.com
patch subject: [PATCH 18/18] KVM: arm64: Plumb the pKVM MMU in KVM
config: arm64-randconfig-002-20241105 (https://download.01.org/0day-ci/archive/20241105/202411051325.EBkzE0th-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 14.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241105/202411051325.EBkzE0th-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411051325.EBkzE0th-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/arm64/kvm/mmu.c:338: warning: Function parameter or struct member 'pgt' not described in 'kvm_s2_unmap'
>> arch/arm64/kvm/mmu.c:338: warning: Function parameter or struct member 'addr' not described in 'kvm_s2_unmap'
>> arch/arm64/kvm/mmu.c:338: warning: expecting prototype for __unmap_stage2_range(). Prototype was for kvm_s2_unmap() instead


vim +338 arch/arm64/kvm/mmu.c

   299	
   300	/*
   301	 * Unmapping vs dcache management:
   302	 *
   303	 * If a guest maps certain memory pages as uncached, all writes will
   304	 * bypass the data cache and go directly to RAM.  However, the CPUs
   305	 * can still speculate reads (not writes) and fill cache lines with
   306	 * data.
   307	 *
   308	 * Those cache lines will be *clean* cache lines though, so a
   309	 * clean+invalidate operation is equivalent to an invalidate
   310	 * operation, because no cache lines are marked dirty.
   311	 *
   312	 * Those clean cache lines could be filled prior to an uncached write
   313	 * by the guest, and the cache coherent IO subsystem would therefore
   314	 * end up writing old data to disk.
   315	 *
   316	 * This is why right after unmapping a page/section and invalidating
   317	 * the corresponding TLBs, we flush to make sure the IO subsystem will
   318	 * never hit in the cache.
   319	 *
   320	 * This is all avoided on systems that have ARM64_HAS_STAGE2_FWB, as
   321	 * we then fully enforce cacheability of RAM, no matter what the guest
   322	 * does.
   323	 */
   324	/**
   325	 * __unmap_stage2_range -- Clear stage2 page table entries to unmap a range
   326	 * @mmu:   The KVM stage-2 MMU pointer
   327	 * @start: The intermediate physical base address of the range to unmap
   328	 * @size:  The size of the area to unmap
   329	 * @may_block: Whether or not we are permitted to block
   330	 *
   331	 * Clear a range of stage-2 mappings, lowering the various ref-counts.  Must
   332	 * be called while holding mmu_lock (unless for freeing the stage2 pgd before
   333	 * destroying the VM), otherwise another faulting VCPU may come in and mess
   334	 * with things behind our backs.
   335	 */
   336	
   337	static int kvm_s2_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size)
 > 338	{
   339		return KVM_PGT_S2(unmap, pgt, addr, size);
   340	}
   341	

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