Re: [PATCH v3 07/17] arm64, hibernate: move page handling function to new trans_pgd.c

On Fri, Sep 6, 2019 at 11:18 AM James Morse [off-list ref] wrote:

Hi Pavel,

On 21/08/2019 19:31, Pavel Tatashin wrote:

quoted

Now, that we abstracted the required functions move them to a new home.
Later, we will generalize these function in order to be useful outside
of hibernation.

quoted

diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
new file mode 100644
index 000000000000..00b62d8640c2
--- /dev/null
+++ b/arch/arm64/mm/trans_pgd.c

@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2019, Microsoft Corporation.
+ * Pavel Tatashin <patatash@linux.microsoft.com>

Hmmm, while line-count isn't a useful metric: this file contains 41% of the code that was
in hibernate.c, but has stripped the substantial copyright-pedigree that the hibernate
code had built up over the years.
(counting lines identified by 'cloc' as code, not comments or blank)

If you are copying or moving a non trivial quantity of code, you need to preserve the
copyright. Something like 'Derived from the arm64 hibernate support which has:'....

I will do that.  The copyright thing was meant to appear in
"generalization" patch that comes later, where I unified most of the
code to be symmetric.
So, I will add it there, and also do the derived message that you suggested.

quoted

+ */
+
+/*
+ * Transitional tables are used during system transferring from one world to
+ * another: such as during hibernate restore, and kexec reboots. During these
+ * phases one cannot rely on page table not being overwritten.

I think you need to mention that hibernate and kexec are rewriting memory, and may
overwrite the live page tables, therefore ...

Will add, thank you.

Pasha

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