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Initialize vm_page_prot to VM_MEMATTR_DEFAULT instead of 0.

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If a driver's Linux mmap callback passed vm_page_prot through unchanged,
then linux_dev_mmap_single() would try to apply whatever VM_MEMATTR_xxx
value 0 is to the mapping.  On x86, VM_MEMATTR_DEFAULT is the PAT value
for write-back (WB) which is 6, while 0 maps to the PAT value for
uncacheable (UC).  Thus, any mmap request that did not explicitly set
page_prot was tried to map memory as UC triggering the warning in
sg_pager_getpages().

Tested by:	np
Reported by:	Krishnamraju Eraparaju @ Chelsio
MFC after:	3 days
Sponsored by:	Chelsio Communications
This commit is contained in:
jhb 2016-01-20 00:14:34 +00:00
parent eef4b2b8aa
commit aae5878eb3
1 changed files with 1 additions and 1 deletions
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2
sys/compat/linuxkpi/common/src/linux_compat.c
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@ -587,7 +587,7 @@ linux_dev_mmap_single(struct cdev *dev, vm_ooffset_t *offset,
vma.vm_end = size;
vma.vm_pgoff = *offset / PAGE_SIZE;
vma.vm_pfn = 0;
vma.vm_page_prot = 0;
vma.vm_page_prot = VM_MEMATTR_DEFAULT;
if (filp->f_op->mmap) {
error = -filp->f_op->mmap(filp, &vma);
if (error == 0) {