[PATCH] kexec: Replace kmap() with kmap_local_page()

[PATCH] kexec: Replace kmap() with kmap_local_page()

[Fabio M. De Francesco]

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


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[PATCH] kexec: Replace kmap() with kmap_local_page()

[Fabio M. De Francesco]

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


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Re: [PATCH] kexec: Replace kmap() with kmap_local_page()

[Fabio M. De Francesco]

On giovedì 7 luglio 2022 20:49:39 CEST Fabio M. De Francesco wrote:
> 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(-)
>
Please discard this version because there is a small error in the commit 
message due to bad copy and paste. Version 2 is at 
https://lore.kernel.org/lkml/20220707231550.1484-1-fmdefrancesco@gmail.com/

Thanks,

Fabio



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Re: [PATCH] kexec: Replace kmap() with kmap_local_page()

[Fabio M. De Francesco]

On venerdì 8 luglio 2022 01:14:12 CEST Fabio M. De Francesco wrote:
> 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(-)
> 
Sorry, another error... Please discard this patch because the version 
number is missing in the subject.

The second version, hopefully final and correct, is at
https://lore.kernel.org/lkml/20220707231550.1484-1-fmdefrancesco@gmail.com/

Thank you,

Fabio




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