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3166851142
If a fault on a kernel address is due to a non-present page, then it
cannot be the result of stale TLB entry from a protection change (RO
to RW or NX to X). Thus the pagetable walk in spurious_fault() can be
skipped.
See the initial if in spurious_fault() and the tests in
spurious_fault_check()) for the set of possible error codes checked
for spurious faults. These are:
IRUWP
Before x00xx && ( 1xxxx || xxx1x )
After ( 10001 || 00011 ) && ( 1xxxx || xxx1x )
Thus the new condition is a subset of the previous one, excluding only
non-present faults (I == 1 and W == 1 are mutually exclusive).
This avoids spurious_fault() oopsing in some cases if the pagetables
it attempts to walk are not accessible. This obscures the location of
the original fault.
This also fixes a crash with Xen PV guests when they access entries in
the M2P corresponding to device MMIO regions. The M2P is mapped
(read-only) by Xen into the kernel address space of the guest and this
mapping may contains holes for non-RAM regions. Read faults will
result in calls to spurious_fault(), but because the page tables for
the M2P mappings are not accessible by the guest the pagetable walk
would fault.
This was not normally a problem as MMIO mappings would not normally
result in a M2P lookup because of the use of the _PAGE_IOMAP bit the
PTE. However, removing the _PAGE_IOMAP bit requires M2P lookups for
MMIO mappings as well.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
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|---|---|---|
| .. | ||
| kmemcheck | ||
| amdtopology.c | ||
| dump_pagetables.c | ||
| extable.c | ||
| fault.c | ||
| gup.c | ||
| highmem_32.c | ||
| hugetlbpage.c | ||
| init_32.c | ||
| init_64.c | ||
| init.c | ||
| iomap_32.c | ||
| ioremap.c | ||
| kmmio.c | ||
| Makefile | ||
| memtest.c | ||
| mm_internal.h | ||
| mmap.c | ||
| mmio-mod.c | ||
| numa_32.c | ||
| numa_64.c | ||
| numa_emulation.c | ||
| numa_internal.h | ||
| numa.c | ||
| pageattr-test.c | ||
| pageattr.c | ||
| pat_internal.h | ||
| pat_rbtree.c | ||
| pat.c | ||
| pf_in.c | ||
| pf_in.h | ||
| pgtable_32.c | ||
| pgtable.c | ||
| physaddr.c | ||
| physaddr.h | ||
| setup_nx.c | ||
| srat.c | ||
| testmmiotrace.c | ||
| tlb.c | ||