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From: Hans de Goede <hdegoede@redhat.com>
To: Arvind Sankar <nivedita@alum.mit.edu>, Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-crypto@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	Stephan Mueller <smueller@chronox.de>,
	linux-s390@vger.kernel.org
Subject: Re: [PATCH v2 5.4 regression fix] x86/boot: Provide memzero_explicit
Date: Mon, 7 Oct 2019 21:36:25 +0200
Message-ID: <1d17349e-98ab-b582-6981-b484b0e970b6@redhat.com> (raw)
In-Reply-To: <20191007184237.GB13589@rani.riverdale.lan>

Hi,

On 07-10-2019 20:42, Arvind Sankar wrote:
> On Mon, Oct 07, 2019 at 05:40:07PM +0200, Ingo Molnar wrote:
>>
>> * Arvind Sankar <nivedita@alum.mit.edu> wrote:
>>
>>> With the barrier in there, is there any reason to *not* inline the
>>> function? barrier_data() is an asm statement that tells the compiler
>>> that the asm uses the memory that was set to zero, thus preventing it
>>> from removing the memset even if nothing else uses that memory later. A
>>> more detailed comment is there in compiler-gcc.h. I can't see why it
>>> wouldn't work even if it were inlined.
>>>
>>> If the function can indeed be inlined, we could just make the common
>>> implementation a macro and avoid duplicating it? As mentioned in another
>>> mail, we otherwise will likely need another duplicate implementation for
>>> arch/s390/purgatory as well.
>>
>> I suspect macro would be justified in this case. Mind sending a v3 patch
>> to demonstrate how it would all look like?
>>
>> I'll zap v2 if the macro solution looks better.
>>
>> Thanks,
>>
>> 	Ingo
> 
> Patch attached to turn memzero_explicit into inline function.

Hehe, I had prepared and have just tested the exact same patch
(only the commit msg was different).

I've just booted a kernel build with that patch and that works
fine (as expected).

So your patch is:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>

Since this is a bit of a core change though, I think it is
best if you send it to the linux-kernel list (with my tags from above
added) as is normally done for kernel patches. Then others, who may
not be following this thread, will get a chance to give feedback on it.

Regards,

Hans

  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-07 13:47 Hans de Goede
2019-10-07 14:00 ` Ingo Molnar
2019-10-07 14:11   ` Hans de Goede
2019-10-07 14:22     ` Ingo Molnar
2019-10-07 14:29       ` Hans de Goede
2019-10-07 14:46         ` Ingo Molnar
2019-10-07 15:20           ` Arvind Sankar
2019-10-07 15:40             ` Ingo Molnar
2019-10-07 18:42               ` Arvind Sankar
2019-10-07 19:36                 ` Hans de Goede [this message]
2019-10-07 22:00                   ` [PATCH] lib/string: make memzero_explicit inline instead of external Arvind Sankar
2019-10-08 11:33                     ` [tip: x86/urgent] lib/string: Make memzero_explicit() " tip-bot2 for Arvind Sankar
2019-10-08 11:33                     ` tip-bot2 for Arvind Sankar
2019-10-10  2:52                     ` [PATCH] lib/string: make memzero_explicit " Dave Young
2019-10-10  6:56                       ` Dave Young
2019-10-07 14:49 ` [tip: x86/urgent] x86/boot: Provide memzero_explicit() tip-bot2 for Hans de Goede
2019-10-07 14:49 ` tip-bot2 for Hans de Goede

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