linux-kernel - [PATCH] KVM: SVM: Replace kmap_atomic() with kmap_local

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Date:   Fri,  2 Sep 2022 17:08:11 +0800
From:   Zhao Liu <zhao1.liu@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Ira Weiny <ira.weiny@...el.com>,
        "Fabio M . De Francesco" <fmdefrancesco@...il.com>,
        Zhenyu Wang <zhenyu.z.wang@...el.com>,
        Zhao Liu <zhao1.liu@...el.com>
Subject: [PATCH] KVM: SVM: Replace kmap_atomic() with kmap_local_page()

From: Zhao Liu <zhao1.liu@...el.com>

The use of kmap_atomic() is being deprecated in favor of
kmap_local_page()[1].

In arch/x86/kvm/svm/sev.c, the function sev_clflush_pages() doesn't
need to disable pagefaults and preemption in kmap_atomic(). It can
simply use kmap_local_page() / kunmap_local() that can instead do the
mapping / unmapping regardless of the context.

With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Therefore, sev_clflush_pages() is a function where
the use of kmap_local_page() in place of kmap_atomic() is correctly
suited.

Convert the calls of kmap_atomic() / kunmap_atomic() to
kmap_local_page() / kunmap_local().

[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com

Suggested-by: Ira Weiny <ira.weiny@...el.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
Signed-off-by: Zhao Liu <zhao1.liu@...el.com>
---
Suggested by credits.
        Ira: Referred to his task document and review comments.
        Fabio: Referred to his boiler plate commit message.
---
 arch/x86/kvm/svm/sev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 28064060413a..12747c7bda4e 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -465,9 +465,9 @@ static void sev_clflush_pages(struct page *pages[], unsigned long npages)
 		return;
 
 	for (i = 0; i < npages; i++) {
-		page_virtual = kmap_atomic(pages[i]);
+		page_virtual = kmap_local_page(pages[i]);
 		clflush_cache_range(page_virtual, PAGE_SIZE);
-		kunmap_atomic(page_virtual);
+		kunmap_local(page_virtual);
 		cond_resched();
 	}
 }
-- 
2.34.1