From: Ying-Tsun Huang ying-tsun.huang@amd.com
commit cb7f4a8b1fb426a175d1708f05581939c61329d4 upstream.
In mtrr_type_lookup(), if the input memory address region is not in the MTRR, over 4GB, and not over the top of memory, a write-back attribute is returned. These condition checks are for ensuring the input memory address region is actually mapped to the physical memory.
However, if the end address is just aligned with the top of memory, the condition check treats the address is over the top of memory, and write-back attribute is not returned.
And this hits in a real use case with NVDIMM: the nd_pmem module tries to map NVDIMMs as cacheable memories when NVDIMMs are connected. If a NVDIMM is the last of the DIMMs, the performance of this NVDIMM becomes very low since it is aligned with the top of memory and its memory type is uncached-minus.
Move the input end address change to inclusive up into mtrr_type_lookup(), before checking for the top of memory in either mtrr_type_lookup_{variable,fixed}() helpers.
[ bp: Massage commit message. ]
Fixes: 0cc705f56e40 ("x86/mm/mtrr: Clean up mtrr_type_lookup()") Signed-off-by: Ying-Tsun Huang ying-tsun.huang@amd.com Signed-off-by: Borislav Petkov bp@suse.de Link: https://lkml.kernel.org/r/20201215070721.4349-1-ying-tsun.huang@amd.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/mtrr/generic.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c index e12ee86906c6..9436f3452049 100644 --- a/arch/x86/kernel/cpu/mtrr/generic.c +++ b/arch/x86/kernel/cpu/mtrr/generic.c @@ -166,9 +166,6 @@ static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end, *repeat = 0; *uniform = 1;
- /* Make end inclusive instead of exclusive */ - end--; - prev_match = MTRR_TYPE_INVALID; for (i = 0; i < num_var_ranges; ++i) { unsigned short start_state, end_state, inclusive; @@ -260,6 +257,9 @@ u8 mtrr_type_lookup(u64 start, u64 end, u8 *uniform) int repeat; u64 partial_end;
+ /* Make end inclusive instead of exclusive */ + end--; + if (!mtrr_state_set) return MTRR_TYPE_INVALID;