From: Krish Sadhukhan <[email protected]>
commit 75d1cc0e05af579301ce4e49cf6399be4b4e6e76 upstream.
In some hardware implementations, coherency between the encrypted and
unencrypted mappings of the same physical page is enforced. In such a
system, it is not required for software to flush the page from all CPU
caches in the system prior to changing the value of the C-bit for the
page. So check that bit before flushing the cache.
[ bp: Massage commit message. ]
Suggested-by: Tom Lendacky <[email protected]>
Signed-off-by: Krish Sadhukhan <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Liam Merwick <[email protected]>
---
arch/x86/mm/pageattr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 281e584cfe39..d61313f5c5b9 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1967,7 +1967,7 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
/*
* Before changing the encryption attribute, we need to flush caches.
*/
- cpa_flush(&cpa, 1);
+ cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT));
ret = __change_page_attr_set_clr(&cpa, 1);
--
2.27.0