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linux_dma: Ensure proper flags pass to allocators.
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Authored by bdrewery on Dec 8 2020, 5:44 AM.

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rstone
• hselasky

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rS368524: linux_dma: Ensure proper flags pass to allocators.

Summary

No functional change intended.

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rS FreeBSD src repository - subversion

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bdrewery created this revision.Dec 8 2020, 5:44 AM

Herald added subscribers: linuxkpi, emaste, imp. · View Herald TranscriptDec 8 2020, 5:44 AM

bdrewery requested review of this revision.Dec 8 2020, 5:44 AM

Harbormaster completed remote builds in B35249: Diff 80432.Dec 8 2020, 5:45 AM

bdrewery edited the summary of this revision. (Show Details)Dec 8 2020, 5:53 AM

bdrewery added a reviewer: • hselasky.Dec 8 2020, 11:14 PM

Hi,

Can you explain this change a bit more?

gfp_t may contain bits which are not supported by the M_XXX flags and should be filtered away?

If you need to pass additional flags you need to update GFP_NATIVE_MASK .

--HPS

In D27508#615133, @hselasky wrote:

Hi,

Can you explain this change a bit more?

gfp_t may contain bits which are not supported by the M_XXX flags and should be filtered away?

If you need to pass additional flags you need to update GFP_NATIVE_MASK .

--HPS

% git grep GFP_NATIVE_MASK sys
sys/compat/linuxkpi/common/include/linux/gfp.h:#define  GFP_NATIVE_MASK (M_NOWAIT | M_WAITOK | M_USE_RESERVE | M_ZERO)
sys/compat/linuxkpi/common/include/linux/gfp.h:CTASSERT((__GFP_DMA32 & GFP_NATIVE_MASK) == 0);
sys/compat/linuxkpi/common/include/linux/gfp.h:CTASSERT((__GFP_BITS_MASK & GFP_NATIVE_MASK) == GFP_NATIVE_MASK);
sys/compat/linuxkpi/common/include/linux/slab.h:        return (flags & GFP_NATIVE_MASK);
sys/compat/linuxkpi/common/src/linux_page.c:            addr = kmem_malloc(size, flags & GFP_NATIVE_MASK);
sys/compat/linuxkpi/common/src/linux_page.c:            addr = kmem_alloc_contig(size, flags & GFP_NATIVE_MASK, 0,

While reviewing the code here, I noticed the kmem_malloc and kmem_alloc_contig in linux_page.c were masking but not the calls in linux_pci.c. Yes this masks to only pass the acceptable M_ flags.

	if (priv->dma_mask)
		high = priv->dma_mask;
	else if (flag & GFP_DMA32)                                 //////////////////////////// here
		high = BUS_SPACE_MAXADDR_32BIT;
	else
		high = BUS_SPACE_MAXADDR;
	align = PAGE_SIZE << get_order(size);
	mem = (void *)kmem_alloc_contig(size, flag, 0, high, align, 0,
	    VM_MEMATTR_DEFAULT);

It looks like GFP_DMA32 may be set in flag, 1 << 24 which isn't a normal flag kmem_alloc_contig should be seeing. It appears harmless currently.

Then there is a possible bug in linux_pci.c

Mixed right and left side. Thought you were removing the GFP_NATIVE_MASK.

This revision is now accepted and ready to land.Dec 9 2020, 8:40 PM

Closed by commit rS368524: linux_dma: Ensure proper flags pass to allocators. (authored by bdrewery). · Explain WhyDec 10 2020, 8:45 PM

This revision was automatically updated to reflect the committed changes.

bdrewery added a commit: rS368524: linux_dma: Ensure proper flags pass to allocators..

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head/

sys/

compat/

linuxkpi/

common/

src/

linux_pci.c

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head/sys/compat/linuxkpi/common/src/linux_pci.c

linux_dma: Ensure proper flags pass to allocators.ClosedPublicActions