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| author | Zhao Liu <zhao1.liu@intel.com> | 2022-09-28 12:27:48 +0300 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2022-12-01 03:13:09 +0300 |
| commit | a8a12c0069b9e3c909b3c22bf8711d2f18a0af97 (patch) | |
| tree | ec38dfa28a8e7efe17fe7cbf33b8683afa5d74b3 /arch/x86/kvm/svm | |
| parent | 5c30e8101e8d5d020b1d7119117889756a6ed713 (diff) | |
| download | linux-a8a12c0069b9e3c909b3c22bf8711d2f18a0af97.tar.xz | |
KVM: SVM: Replace kmap_atomic() with kmap_local_page()
The use of kmap_atomic() is being deprecated in favor of
kmap_local_page()[1].
The main difference between atomic and local mappings is that local
mappings don't disable page faults or preemption.
There're 2 reasons we can use kmap_local_page() here:
1. SEV is 64-bit only and kmap_local_page() doesn't disable migration in
this case, but here the function clflush_cache_range() uses CLFLUSHOPT
instruction to flush, and on x86 CLFLUSHOPT is not CPU-local and flushes
the page out of the entire cache hierarchy on all CPUs (APM volume 3,
chapter 3, CLFLUSHOPT). So there's no need to disable preemption to ensure
CPU-local.
2. clflush_cache_range() doesn't need to disable pagefault and the mapping
is still valid even if sleeps. This is also true for sched out/in when
preempted.
In addition, though kmap_local_page() is a thin wrapper around
page_address() on 64-bit, kmap_local_page() should still be used here in
preference to page_address() since page_address() isn't suitable to be used
in a generic function (like sev_clflush_pages()) where the page passed in
is not easy to determine the source of allocation. Keeping the kmap* API in
place means it can be used for things other than highmem mappings[2].
Therefore, sev_clflush_pages() is a function that should use
kmap_local_page() in place of kmap_atomic().
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
[2]: https://lore.kernel.org/lkml/5d667258-b58b-3d28-3609-e7914c99b31b@intel.com/
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220928092748.463631-1-zhao1.liu@linux.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/svm')
| -rw-r--r-- | arch/x86/kvm/svm/sev.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 69dbf17f0d6a..86d6897f4806 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(); } } |