linux-toradex.git/mm/hmm.c, branch v4.17-rc7

mm/hmm.c: remove superfluous RCU protection around radix tree lookup

2018-04-11T17:28:31+00:00

hmm_devmem_find() requires rcu_read_lock_held() but there's nothing which
actually uses the RCU protection.  The only caller is
hmm_devmem_pages_create() which already grabs the mutex and does
superfluous rcu_read_lock/unlock() around the function.

This doesn't add anything and just adds to confusion.  Remove the RCU
protection and open-code the radix tree lookup.  If this needs to become
more sophisticated in the future, let's add them back when necessary.

Link: http://lkml.kernel.org/r/20180314194515.1661824-4-tj@kernel.org
Signed-off-by: Tejun Heo 
Reviewed-by: Jérôme Glisse 
Cc: Paul E. McKenney 
Cc: Benjamin LaHaise 
Cc: Al Viro 
Cc: Kent Overstreet 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: use device driver encoding for HMM pfn

2018-04-11T17:28:31+00:00

Users of hmm_vma_fault() and hmm_vma_get_pfns() provide a flags array and
pfn shift value allowing them to define their own encoding for HMM pfn
that are fill inside the pfns array of the hmm_range struct.  With this
device driver can get pfn that match their own private encoding out of HMM
without having to do any conversion.

[rcampbell@nvidia.com: don't ignore specific pte fault flag in hmm_vma_fault()]
  Link: http://lkml.kernel.org/r/20180326213009.2460-2-jglisse@redhat.com
[rcampbell@nvidia.com: clarify fault logic for device private memory]
  Link: http://lkml.kernel.org/r/20180326213009.2460-3-jglisse@redhat.com
Link: http://lkml.kernel.org/r/20180323005527.758-16-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Signed-off-by: Ralph Campbell 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Cc: John Hubbard 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: change hmm_vma_fault() to allow write fault on page basis

2018-04-11T17:28:31+00:00

This changes hmm_vma_fault() to not take a global write fault flag for a
range but instead rely on caller to populate HMM pfns array with proper
fault flag ie HMM_PFN_VALID if driver want read fault for that address or
HMM_PFN_VALID and HMM_PFN_WRITE for write.

Moreover by setting HMM_PFN_DEVICE_PRIVATE the device driver can ask for
device private memory to be migrated back to system memory through page
fault.

This is more flexible API and it better reflects how device handles and
reports fault.

Link: http://lkml.kernel.org/r/20180323005527.758-15-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Cc: John Hubbard 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: factor out pte and pmd handling to simplify hmm_vma_walk_pmd()

2018-04-11T17:28:31+00:00

No functional change, just create one function to handle pmd and one to
handle pte (hmm_vma_handle_pmd() and hmm_vma_handle_pte()).

Link: http://lkml.kernel.org/r/20180323005527.758-14-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: move hmm_pfns_clear() closer to where it is used

2018-04-11T17:28:30+00:00

Move hmm_pfns_clear() closer to where it is used to make it clear it is
not use by page table walkers.

Link: http://lkml.kernel.org/r/20180323005527.758-13-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: rename HMM_PFN_DEVICE_UNADDRESSABLE to HMM_PFN_DEVICE_PRIVATE

2018-04-11T17:28:30+00:00

Make naming consistent across code, DEVICE_PRIVATE is the name use outside
HMM code so use that one.

Link: http://lkml.kernel.org/r/20180323005527.758-12-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: do not differentiate between empty entry or missing directory

2018-04-11T17:28:30+00:00

There is no point in differentiating between a range for which there is
not even a directory (and thus entries) and empty entry (pte_none() or
pmd_none() returns true).

Simply drop the distinction ie remove HMM_PFN_EMPTY flag and merge now
duplicate hmm_vma_walk_hole() and hmm_vma_walk_clear() functions.

Link: http://lkml.kernel.org/r/20180323005527.758-11-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: cleanup special vma handling (VM_SPECIAL)

2018-04-11T17:28:30+00:00

Special vma (one with any of the VM_SPECIAL flags) can not be access by
device because there is no consistent model across device drivers on those
vma and their backing memory.

This patch directly use hmm_range struct for hmm_pfns_special() argument
as it is always affecting the whole vma and thus the whole range.

It also make behavior consistent after this patch both hmm_vma_fault() and
hmm_vma_get_pfns() returns -EINVAL when facing such vma.  Previously
hmm_vma_fault() returned 0 and hmm_vma_get_pfns() return -EINVAL but both
were filling the HMM pfn array with special entry.

Link: http://lkml.kernel.org/r/20180323005527.758-10-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: use uint64_t for HMM pfn instead of defining hmm_pfn_t to ulong

2018-04-11T17:28:30+00:00

All device driver we care about are using 64bits page table entry.  In
order to match this and to avoid useless define convert all HMM pfn to
directly use uint64_t.  It is a first step on the road to allow driver to
directly use pfn value return by HMM (saving memory and CPU cycles use for
conversion between the two).

Link: http://lkml.kernel.org/r/20180323005527.758-9-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hmm: remove HMM_PFN_READ flag and ignore peculiar architecture

2018-04-11T17:28:30+00:00

Only peculiar architecture allow write without read thus assume that any
valid pfn do allow for read.  Note we do not care for write only because
it does make sense with thing like atomic compare and exchange or any
other operations that allow you to get the memory value through them.

Link: http://lkml.kernel.org/r/20180323005527.758-8-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Reviewed-by: John Hubbard 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds