x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case
Since72cbc8f04f
("x86/PAT: Have pat_enabled() properly reflect state when running on Xen") PAT can be enabled without MTRR. This has resulted in problems e.g. for a SEV-SNP guest running under Hyper-V, when trying to establish a new mapping via memremap() with WB caching mode, as pat_x_mtrr_type() will call mtrr_type_lookup(), which in turn is returning MTRR_TYPE_INVALID due to MTRR being disabled in this configuration. The result is a mapping with UC- caching, leading to severe performance degradation. Fix that by handling MTRR_TYPE_INVALID the same way as MTRR_TYPE_WRBACK in pat_x_mtrr_type() because MTRR_TYPE_INVALID means MTRRs are disabled. [ bp: Massage commit message. ] Fixes:72cbc8f04f
("x86/PAT: Have pat_enabled() properly reflect state when running on Xen") Reported-by: Michael Kelley (LINUX) <mikelley@microsoft.com> Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Tested-by: Michael Kelley <mikelley@microsoft.com> Cc: <stable@kernel.org> Link: https://lore.kernel.org/r/20230110065427.20767-1-jgross@suse.com
This commit is contained in:
parent
7c6dd961d0
commit
90b926e68f
|
@ -387,7 +387,8 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end,
|
|||
u8 mtrr_type, uniform;
|
||||
|
||||
mtrr_type = mtrr_type_lookup(start, end, &uniform);
|
||||
if (mtrr_type != MTRR_TYPE_WRBACK)
|
||||
if (mtrr_type != MTRR_TYPE_WRBACK &&
|
||||
mtrr_type != MTRR_TYPE_INVALID)
|
||||
return _PAGE_CACHE_MODE_UC_MINUS;
|
||||
|
||||
return _PAGE_CACHE_MODE_WB;
|
||||
|
|
Loading…
Reference in New Issue