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

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Message-ID: <76d9d338-2fc1-a8a5-8f12-c25d2ad092f3@redhat.com>
Date:   Sat, 29 Sep 2018 17:36:04 +0800
From:   lijiang <lijiang@...hat.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, thomas.lendacky@....com,
        bhelgaas@...gle.com, baiyaowei@...s.chinamobile.com, tiwai@...e.de,
        brijesh.singh@....com, dyoung@...hat.com, bhe@...hat.com,
        jroedel@...e.de
Subject: Re: [PATCH v7 RESEND 4/4] kdump/vmcore: support encrypted old memory
 with SME enabled

在 2018年09月29日 16:30, Borislav Petkov 写道:
> 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.
> 

Great! Previously i was afraid that the maintainer might disagree with
rewriting the function copy_oldmem_page().

That's really great. I will modify this patch and post the series again.

Thanks.
Lianbo
> 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?
> 
Yes, got it. Thanks for your valuable time and patience.

Regards,
Lianbo