kernel.git/mm/hmm.c, branch linux-5.5.y

mm/hmm: remove hmm_range_dma_map and hmm_range_dma_unmap

2019-11-23T23:56:45Z

These two functions have never been used since they were added. Link: https://lore.kernel.org/r/20191113134528.21187-1-hch@lst.de Signed-off-by: Christoph Hellwig Reviewed-by: John Hubbard Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe

mm/hmm: make full use of walk_page_range()

2019-11-23T23:56:45Z

hmm_range_fault() calls find_vma() and walk_page_range() in a loop. This is unnecessary duplication since walk_page_range() calls find_vma() in a loop already. Simplify hmm_range_fault() by defining a walk_test() callback function to filter unhandled vmas. This also fixes a bug where hmm_range_fault() was not checking start >= vma->vm_start before checking vma->vm_flags so hmm_range_fault() could return an error based on the wrong vma for the requested range. It also fixes a bug when the vma has no read access and the caller did not request a fault, there shouldn't be any error return code. Link: https://lore.kernel.org/r/20191104222141.5173-2-rcampbell@nvidia.com Signed-off-by: Ralph Campbell Reviewed-by: Christoph Hellwig Signed-off-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe

mm/hmm: remove hmm_mirror and related

2019-11-23T23:56:45Z

The only two users of this are now converted to use mmu_interval_notifier, delete all the code and update hmm.rst. Link: https://lore.kernel.org/r/20191112202231.3856-14-jgg@ziepe.ca Reviewed-by: Jérôme Glisse Tested-by: Ralph Campbell Reviewed-by: Christoph Hellwig Signed-off-by: Jason Gunthorpe

mm/hmm: allow hmm_range to be used with a mmu_interval_notifier or hmm_mirror

2019-11-23T23:56:44Z

hmm_mirror's handling of ranges does not use a sequence count which results in this bug: CPU0 CPU1 hmm_range_wait_until_valid(range) valid == true hmm_range_fault(range) hmm_invalidate_range_start() range->valid = false hmm_invalidate_range_end() range->valid = true hmm_range_valid(range) valid == true Where the hmm_range_valid() should not have succeeded. Adding the required sequence count would make it nearly identical to the new mmu_interval_notifier. Instead replace the hmm_mirror stuff with mmu_interval_notifier. Co-existence of the two APIs is the first step. Link: https://lore.kernel.org/r/20191112202231.3856-4-jgg@ziepe.ca Reviewed-by: Jérôme Glisse Tested-by: Philip Yang Tested-by: Ralph Campbell Reviewed-by: Christoph Hellwig Signed-off-by: Jason Gunthorpe

mm/hmm: allow snapshot of the special zero page

2019-10-29T17:26:28Z

If a device driver like nouveau tries to use hmm_range_fault() to access the special shared zero page in system memory, hmm_range_fault() will return -EFAULT and kill the process. Allow hmm_range_fault() to return success (0) when the CPU pagetable entry points to the special shared zero page. page_to_pfn() and pfn_to_page() are defined on the zero page so just handle it like any other page. Link: https://lore.kernel.org/r/20191023195515.13168-3-rcampbell@nvidia.com Signed-off-by: Ralph Campbell Reviewed-by: "Jérôme Glisse" Acked-by: David Hildenbrand Signed-off-by: Jason Gunthorpe

pagewalk: separate function pointers from iterator data

2019-09-07T07:28:04Z

The mm_walk structure currently mixed data and code. Split out the operations vectors into a new mm_walk_ops structure, and while we are changing the API also declare the mm_walk structure inside the walk_page_range and walk_page_vma functions. Based on patch from Linus Torvalds. Link: https://lore.kernel.org/r/20190828141955.22210-3-hch@lst.de Signed-off-by: Christoph Hellwig Reviewed-by: Thomas Hellstrom Reviewed-by: Steven Price Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe

mm: split out a new pagewalk.h header from mm.h

2019-09-07T07:28:04Z

Add a new header for the two handful of users of the walk_page_range / walk_page_vma interface instead of polluting all users of mm.h with it. Link: https://lore.kernel.org/r/20190828141955.22210-2-hch@lst.de Signed-off-by: Christoph Hellwig Reviewed-by: Thomas Hellstrom Reviewed-by: Steven Price Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe

mm/hmm: hmm_range_fault() infinite loop

2019-08-27T22:27:07Z

Normally, callers to handle_mm_fault() are supposed to check the vma->vm_flags first. hmm_range_fault() checks for VM_READ but doesn't check for VM_WRITE if the caller requests a page to be faulted in with write permission (via the hmm_range.pfns[] value). If the vma is write protected, this can result in an infinite loop: hmm_range_fault() walk_page_range() ... hmm_vma_walk_hole() hmm_vma_walk_hole_() hmm_vma_do_fault() handle_mm_fault(FAULT_FLAG_WRITE) /* returns VM_FAULT_WRITE */ /* returns -EBUSY */ /* returns -EBUSY */ /* returns -EBUSY */ /* loops on -EBUSY and range->valid */ Prevent this by checking for vma->vm_flags & VM_WRITE before calling handle_mm_fault(). Link: https://lore.kernel.org/r/20190823221753.2514-3-rcampbell@nvidia.com Signed-off-by: Ralph Campbell Reviewed-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe

mm/hmm: hmm_range_fault() NULL pointer bug

2019-08-27T22:27:07Z

Although hmm_range_fault() calls find_vma() to make sure that a vma exists before calling walk_page_range(), hmm_vma_walk_hole() can still be called with walk->vma == NULL if the start and end address are not contained within the vma range. hmm_range_fault() /* calls find_vma() but no range check */ walk_page_range() /* calls find_vma(), sets walk->vma = NULL */ __walk_page_range() walk_pgd_range() walk_p4d_range() walk_pud_range() hmm_vma_walk_hole() hmm_vma_walk_hole_() hmm_vma_do_fault() handle_mm_fault(vma=0) Link: https://lore.kernel.org/r/20190823221753.2514-2-rcampbell@nvidia.com Signed-off-by: Ralph Campbell Reviewed-by: Christoph Hellwig Signed-off-by: Jason Gunthorpe

mm/hmm: fix hmm_range_fault()'s handling of swapped out pages

2019-08-23T13:22:20Z

hmm_range_fault() may return NULL pages because some of the pfns are equal to HMM_PFN_NONE. This happens randomly under memory pressure. The reason is during the swapped out page pte path, hmm_vma_handle_pte() doesn't update the fault variable from cpu_flags, so it failed to call hmm_vam_do_fault() to swap the page in. The fix is to call hmm_pte_need_fault() to update fault variable. Fixes: 74eee180b935 ("mm/hmm/mirror: device page fault handler") Link: https://lore.kernel.org/r/20190815205227.7949-1-Philip.Yang@amd.com Signed-off-by: Philip Yang Reviewed-by: "Jérôme Glisse" Signed-off-by: Jason Gunthorpe