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x86/mm/pat: Don't flush cache if hardware enforces cache coherency across encryption domnains
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 <thomas.lendacky@amd.com> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20200917212038.5090-3-krish.sadhukhan@oracle.com
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@ -1999,7 +1999,7 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
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/*
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/*
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* Before changing the encryption attribute, we need to flush caches.
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* Before changing the encryption attribute, we need to flush caches.
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*/
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*/
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cpa_flush(&cpa, 1);
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cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT));
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ret = __change_page_attr_set_clr(&cpa, 1);
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ret = __change_page_attr_set_clr(&cpa, 1);
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