Re: [PATCH v7 RESEND 4/4] kdump/vmcore: support encrypted old memory with SME enabled

[Borislav Petkov <bp@suse.de>]

On Sat, Sep 29, 2018 at 02:24:52PM +0800, lijiang wrote:
> At first, i added an input parameter for read_from_oldmem() because of encryption(SME). But
> for avoiding to also add the same parameter for copy_oldmem_page(), so i added a new function
> copy_oldmem_page_encrypted(). Maybe you had noticed that these functions were very similar.

If you have two very similar functions, you add a *static* workhorse function:

static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize, unsigned long offset,
				  int userbuf, bool encrypted)

and you define two wrappers:

copy_oldmem_page()
copy_oldmem_page_encrypted()

which both call __copy_oldmem_page() with the appropriate parameters.

But you do *not* do a separate compilation unit just because. None of
the reasons you've mentioned warrant having a separate compilation
unit while you already have *the* perfect place to put everything -
arch/x86/kernel/crash_dump_64.c

> So sorry, here "oldmem encrypted" means the "old memory is encrypted".

I know what it means - I'm trying to explain to you to write it out
in plain english and not use some strange constructs like "oldmem
encrypted".

A reader would wonder: why is this thing semi-abbreviated and in
quotation marks? Does that mean anything special?

Our comments should not be write-only. So after you've written it, try
to read it as someone who sees the code for the first time and think
hard whether she/he will understand it.

Do you catch my drift now?

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)

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