Hi James,

I am working on an updated version of this patch series. We had back
and forth discussion on the list and off the list about MMU-enabled
series. So, I decided to sync the last series I had with the current
mainline. Address your last comments (those that I can address), and
send it again, so we can take a fresh look. I will reply to some of
your comments, as I address them in the synced version of my series.

On Wed, Apr 29, 2020 at 1:01 PM James Morse [off-list ref] wrote:

Hi Pavel,

On 26/03/2020 03:24, Pavel Tatashin wrote:

quoted

kexec is going to use a different allocator, so make

quoted

trans_pgd_map_page to accept allocator as an argument, and also
kexec is going to use a different map protection, so also pass
it via argument.

This trans_pgd_map_page() used to be create_single_mapping() It creates page tables that
map one page: the relocation code.

Why do you need a different pgprot? Surely PAGE_KERNEL_EXEC is exactly what you want.

For hibernate case yes, but for MMU enabled kexec case, PAGE_KERNEL is
used, because it is used to copy data segments.

quoted

diff --git a/arch/arm64/include/asm/trans_pgd.h b/arch/arm64/include/asm/trans_pgd.h
index 23153c13d1ce..ad5194ad178d 100644
--- a/arch/arm64/include/asm/trans_pgd.h
+++ b/arch/arm64/include/asm/trans_pgd.h

@@ -12,10 +12,24 @@
 #include <linux/types.h>
 #include <asm/pgtable-types.h>

+/*
+ * trans_alloc_page
+ *   - Allocator that should return exactly one zeroed page, if this
+ *    allocator fails, trans_pgd returns -ENOMEM error.

trans_pgd is what you pass in to trans_pgd_map_page() or trans_pgd_create_copy().
Do you mean what those functions return?

I meant to say trans_pgd_*, but I will change the comment to
explicitly say trans_pgd_map_page() and trans_pgd_create_copy() will
return -ENOMEM.

quoted

+ *
+ * trans_alloc_arg
+ *   - Passed to trans_alloc_page as an argument
+ */

quoted

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index 3d6f0fd73591..607bb1fbc349 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c

@@ -195,6 +200,11 @@ static int create_safe_exec_page(void *src_start, size_t length,
                               unsigned long dst_addr,
                               phys_addr_t *phys_dst_addr)
 {
+     struct trans_pgd_info trans_info = {
+             .trans_alloc_page       = hibernate_page_alloc,
+             .trans_alloc_arg        = (void *)GFP_ATOMIC,
+     };

As you need another copy of this in the next patch, is it worth declaring this globally
and making it const?

I think it is alright to have it on the stack instead of permanently
using the data section for this. Plus, we will have a different one
for the kexec case, so having this globally available will make it
strange.

quoted

diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index d20e48520cef..275a79935d7e 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c

@@ -180,8 +185,18 @@ int trans_pgd_create_copy(pgd_t **dst_pgdp, unsigned long start,
      return rc;
 }

-int trans_pgd_map_page(pgd_t *trans_pgd, void *page, unsigned long dst_addr,
-                    pgprot_t pgprot)
+/*
+ * Add map entry to trans_pgd for a base-size page at PTE level.
+ * info:     contains allocator and its argument
+ * trans_pgd:        page table in which new map is added.
+ * page:     page to be mapped.

quoted

+ * dst_addr: new VA address for the pages

~s/pages/page/

This thing only maps one page.

Sure, I will change that.

Thank you,
Pasha

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