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* [PATCH] kexec: Replace kmap() with kmap_local_page()
@ 2022-07-07 18:49 ` Fabio M. De Francesco
  0 siblings, 0 replies; 8+ messages in thread
From: Fabio M. De Francesco @ 2022-07-07 18:49 UTC (permalink / raw)
  To: Eric Biederman, kexec, linux-kernel; +Cc: Fabio M. De Francesco, Ira Weiny

The use of kmap() and kmap_atomic() are being deprecated in favor of
kmap_local_page().

With kmap_local_page(), the mappings are per thread, CPU local and not
globally visible. Furthermore, the mappings can be acquired from any
context (including interrupts).

Therefore, use kmap_local_page() in aio.c because these mappings are per
thread, CPU local, and not globally visible.

Tested on a QEMU + KVM 32-bits VM booting a kernel with HIGHMEM64GB
enabled.

Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
 kernel/kexec_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 4d34c78334ce..6f98274765d4 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -814,7 +814,7 @@ static int kimage_load_normal_segment(struct kimage *image,
 		if (result < 0)
 			goto out;
 
-		ptr = kmap(page);
+		ptr = kmap_local_page(page);
 		/* Start with a clear page */
 		clear_page(ptr);
 		ptr += maddr & ~PAGE_MASK;
@@ -827,7 +827,7 @@ static int kimage_load_normal_segment(struct kimage *image,
 			memcpy(ptr, kbuf, uchunk);
 		else
 			result = copy_from_user(ptr, buf, uchunk);
-		kunmap(page);
+		kunmap_local(ptr);
 		if (result) {
 			result = -EFAULT;
 			goto out;
@@ -878,7 +878,7 @@ static int kimage_load_crash_segment(struct kimage *image,
 			goto out;
 		}
 		arch_kexec_post_alloc_pages(page_address(page), 1, 0);
-		ptr = kmap(page);
+		ptr = kmap_local_page(page);
 		ptr += maddr & ~PAGE_MASK;
 		mchunk = min_t(size_t, mbytes,
 				PAGE_SIZE - (maddr & ~PAGE_MASK));
@@ -894,7 +894,7 @@ static int kimage_load_crash_segment(struct kimage *image,
 		else
 			result = copy_from_user(ptr, buf, uchunk);
 		kexec_flush_icache_page(page);
-		kunmap(page);
+		kunmap_local(ptr);
 		arch_kexec_pre_free_pages(page_address(page), 1);
 		if (result) {
 			result = -EFAULT;
-- 
2.36.1


_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

^ permalink raw reply related	[flat|nested] 8+ messages in thread
* [PATCH] kexec: Replace kmap() with kmap_local_page()
@ 2022-07-07 23:14 ` Fabio M. De Francesco
  0 siblings, 0 replies; 8+ messages in thread
From: Fabio M. De Francesco @ 2022-07-07 23:14 UTC (permalink / raw)
  To: Eric Biederman, kexec, linux-kernel; +Cc: Fabio M. De Francesco, Ira Weiny

The use of kmap() and kmap_atomic() are being deprecated in favor of
kmap_local_page().

With kmap_local_page(), the mappings are per thread, CPU local and not
globally visible. Furthermore, the mappings can be acquired from any
context (including interrupts).

Therefore, use kmap_local_page() in kexec_core.c because these mappings are
per thread, CPU local, and not globally visible.

Tested on a QEMU + KVM 32-bits VM booting a kernel with HIGHMEM64GB
enabled.

Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

v1->v2: A sentence of the commit message contained an error due to a
mistake in copy-pasting from a previous patch. Replace "aio.c" with
"kexec_core.c".

 kernel/kexec_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 4d34c78334ce..6f98274765d4 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -814,7 +814,7 @@ static int kimage_load_normal_segment(struct kimage *image,
 		if (result < 0)
 			goto out;
 
-		ptr = kmap(page);
+		ptr = kmap_local_page(page);
 		/* Start with a clear page */
 		clear_page(ptr);
 		ptr += maddr & ~PAGE_MASK;
@@ -827,7 +827,7 @@ static int kimage_load_normal_segment(struct kimage *image,
 			memcpy(ptr, kbuf, uchunk);
 		else
 			result = copy_from_user(ptr, buf, uchunk);
-		kunmap(page);
+		kunmap_local(ptr);
 		if (result) {
 			result = -EFAULT;
 			goto out;
@@ -878,7 +878,7 @@ static int kimage_load_crash_segment(struct kimage *image,
 			goto out;
 		}
 		arch_kexec_post_alloc_pages(page_address(page), 1, 0);
-		ptr = kmap(page);
+		ptr = kmap_local_page(page);
 		ptr += maddr & ~PAGE_MASK;
 		mchunk = min_t(size_t, mbytes,
 				PAGE_SIZE - (maddr & ~PAGE_MASK));
@@ -894,7 +894,7 @@ static int kimage_load_crash_segment(struct kimage *image,
 		else
 			result = copy_from_user(ptr, buf, uchunk);
 		kexec_flush_icache_page(page);
-		kunmap(page);
+		kunmap_local(ptr);
 		arch_kexec_pre_free_pages(page_address(page), 1);
 		if (result) {
 			result = -EFAULT;
-- 
2.36.1


_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

^ permalink raw reply related	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-07-07 23:51 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-07-07 18:49 [PATCH] kexec: Replace kmap() with kmap_local_page() Fabio M. De Francesco
2022-07-07 18:49 ` Fabio M. De Francesco
2022-07-07 23:40 ` Fabio M. De Francesco
2022-07-07 23:40   ` Fabio M. De Francesco
  -- strict thread matches above, loose matches on Subject: below --
2022-07-07 23:14 Fabio M. De Francesco
2022-07-07 23:14 ` Fabio M. De Francesco
2022-07-07 23:50 ` Fabio M. De Francesco
2022-07-07 23:50   ` Fabio M. De Francesco

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