search for: zone_device

On Fri, May 8, 2020 at 5:00 PM Jason Gunthorpe <jgg at mellanox.com> wrote: > > On Fri, May 08, 2020 at 04:40:09PM +0200, Arnd Bergmann wrote: > > CONFIG_DEVICE_PRIVATE cannot be selected in configurations > > without ZONE_DEVICE: > > It is kind of unfortunate to lift dependencies from DEVICE_PRIVATE > into the users, is this really how kconfig is supposed to work or is > something else wrong here? Usually the problem is trying to use 'select' for something that can be done with 'depends on'. I...

On Thu, Oct 01, 2020 at 11:17:15AM -0700, Ralph Campbell wrote: > ZONE_DEVICE struct pages have an extra reference count that complicates the > code for put_page() and several places in the kernel that need to check the > reference count to see that a page is not being used (gup, compaction, > migration, etc.). Clean up the code so the reference count doesn't ne...

...;> Not true. The page_free() callback records the page is free by setting >> a bit or putting the page on a free list but when it allocates a free >> device private struct page to be used with migrate_vma_setup(), it needs to >> increment the refcount. >> >> For the ZONE_DEVICE MEMORY_DEVICE_GENERIC and MEMORY_DEVICE_PCI_P2PDMA >> struct pages, I think you are correct because they don't define page_free() >> and from what I can see, don't decrement the page refcount to zero. > > Umm, the whole point of ZONE_DEVICE is to have a struct page for &g...

...es even cares about > the page refcount. > Not true. The page_free() callback records the page is free by setting a bit or putting the page on a free list but when it allocates a free device private struct page to be used with migrate_vma_setup(), it needs to increment the refcount. For the ZONE_DEVICE MEMORY_DEVICE_GENERIC and MEMORY_DEVICE_PCI_P2PDMA struct pages, I think you are correct because they don't define page_free() and from what I can see, don't decrement the page refcount to zero.

CONFIG_DEVICE_PRIVATE cannot be selected in configurations without ZONE_DEVICE: WARNING: unmet direct dependencies detected for DEVICE_PRIVATE Depends on [n]: ZONE_DEVICE [=n] Selected by [y]: - DRM_NOUVEAU_SVM [=y] && HAS_IOMEM [=y] && DRM_NOUVEAU [=y] && MMU [=y] && STAGING [=y] kernel/resource.c:1653:28: error: use of undeclared ident...

This is still an RFC because after looking at the pmem/dax code some more, I realized that the ZONE_DEVICE struct pages are being inserted into the process' page tables with vmf_insert_mixed() and a zero refcount on the ZONE_DEVICE struct page. This is sort of OK because insert_pfn() increments the reference count on the pgmap which is what prevents memunmap_pages() from freeing the struct pages and...

On Thu, Oct 01, 2020 at 11:17:15AM -0700, Ralph Campbell wrote: > ZONE_DEVICE struct pages have an extra reference count that complicates the > code for put_page() and several places in the kernel that need to check the > reference count to see that a page is not being used (gup, compaction, > migration, etc.). Clean up the code so the reference count doesn't ne...

From: YueHaibing <yuehaibing at huawei.com> During randconfig builds, I occasionally run into an invalid configuration WARNING: unmet direct dependencies detected for DEVICE_PRIVATE Depends on [n]: ARCH_HAS_HMM_DEVICE [=n] && ZONE_DEVICE [=n] Selected by [y]: - DRM_NOUVEAU_SVM [=y] && HAS_IOMEM [=y] && ARCH_HAS_HMM [=y] && DRM_NOUVEAU [=y] && STAGING [=y] mm/memory.o: In function `do_swap_page': memory.c:(.text+0x2754): undefined reference to `device_private_entry_fault' commit 5da25090...

On Mon, Sep 14, 2020 at 3:45 PM Ralph Campbell <rcampbell at nvidia.com> wrote: > > ZONE_DEVICE struct pages have an extra reference count that complicates the > code for put_page() and several places in the kernel that need to check the > reference count to see that a page is not being used (gup, compaction, > migration, etc.). Clean up the code so the reference count doesn't ne...

On 9/14/20 4:10 PM, Dan Williams wrote: > On Mon, Sep 14, 2020 at 3:45 PM Ralph Campbell <rcampbell at nvidia.com> wrote: >> >> ZONE_DEVICE struct pages have an extra reference count that complicates the >> code for put_page() and several places in the kernel that need to check the >> reference count to see that a page is not being used (gup, compaction, >> migration, etc.). Clean up the code so the reference count do...

...e refcount. >> > Not true. The page_free() callback records the page is free by setting > a bit or putting the page on a free list but when it allocates a free > device private struct page to be used with migrate_vma_setup(), it needs to > increment the refcount. > > For the ZONE_DEVICE MEMORY_DEVICE_GENERIC and MEMORY_DEVICE_PCI_P2PDMA > struct pages, I think you are correct because they don't define page_free() > and from what I can see, don't decrement the page refcount to zero. Umm, the whole point of ZONE_DEVICE is to have a struct page for something that is no...

Matthew Wilcox, Ira Weiny, and others have complained that ZONE_DEVICE struct page reference counting is ugly because they are "free" when the reference count is one instead of zero. This leads to explicit checks for ZONE_DEVICE pages in places like put_page(), GUP, THP splitting, and page migration which have to adjust the expected reference count when dete...

On Fri, Nov 06, 2020 at 01:26:50PM -0800, Ralph Campbell wrote: > > On 11/6/20 12:03 AM, Christoph Hellwig wrote: >> I hate the extra pin count magic here. IMHO we really need to finish >> off the series to get rid of the extra references on the ZONE_DEVICE >> pages first. > > First, thanks for the review comments. > > I don't like the extra refcount either, that is why I tried to fix that up > before resending this series. However, you didn't like me just fixing the > refcount only for device private pages and I don...

I hate the extra pin count magic here. IMHO we really need to finish off the series to get rid of the extra references on the ZONE_DEVICE pages first.

On Fri, Sep 25, 2020 at 01:44:42PM -0700, Ralph Campbell wrote: > ZONE_DEVICE struct pages have an extra reference count that complicates the > code for put_page() and several places in the kernel that need to check the > reference count to see that a page is not being used (gup, compaction, > migration, etc.). Clean up the code so the reference count doesn't ne...

ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treate...

ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treate...

On Thu, Aug 15, 2019 at 08:54:46PM -0700, Dan Williams wrote: > > However, this means we cannot do any processing of ZONE_DEVICE pages > > outside the driver lock, so eg, doing any DMA map that might rely on > > MEMORY_DEVICE_PCI_P2PDMA has to be done in the driver lock, which is > > a bit unfortunate. > > Wouldn't P2PDMA use page pins? Not needing to hold a lock over > ZONE_DEVICE page operat...

ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treate...

On Mon, Sep 14, 2020 at 04:53:25PM -0700, Ralph Campbell wrote: > Since set_page_refcounted() is defined in mm_interal.h I would have to > move the definition to someplace like page_ref.h or have the drivers > cal init_page_count() or set_page_count() since get_page() calls > VM_BUG_ON_PAGE() if refcount == 0. > I'll move set_page_refcounted() since that is what the page