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From: Borislav Petkov <bp@alien8.de>
To: Ashish Kalra <ashish.kalra@amd.com>
Cc: Thomas.Lendacky@amd.com, Jon.Grimm@amd.com,
	brijesh.singh@amd.com, dave.hansen@linux-intel.com,
	konrad.wilk@oracle.com, peterz@infradead.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	mingo@redhat.com, luto@kernel.org, hpa@zytor.com,
	rientjes@google.com, tglx@linutronix.de, hch@lst.de
Subject: Re: [PATCH v8] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests.
Date: Wed, 9 Dec 2020 13:54:42 +0100	[thread overview]
Message-ID: <20201209125442.GC18203@zn.tnic> (raw)
In-Reply-To: <20201209122907.GA6258@ashkalra_ubuntu_server>

On Wed, Dec 09, 2020 at 12:29:07PM +0000, Ashish Kalra wrote:
> As i mentioned in the main comments above, this cannot be called in
> mem_encrypt_init() as that breaks reserve_crashkernel() which depends
> on SWIOTLB buffer size

Please elaborate how does it break.

> and is called before mem_encrypt_init(), therefore, it needs to be
> called from setup_atch() before reserve_crashkernel().

I know you have your requirements what needs to be called when like all
the other vendors who want to run stuff early in a particular order but
our boot init order is a single fragile mess. So this better be done
right!

Also,

[    0.016630] software IO TLB: swiotlb_adjust:
[    0.017005] reserve_crashkernel:
[    0.050523] software IO TLB: swiotlb_init:

this looks strange - we're doing a swiotlb size adjust before init.

It probably makes sense as in: adjust the size before the SWIOTLB is
initialized so that it uses the correct size but this better be spelled
out.

> I believe that other memory encryption architectures such as s390 are
> also looking for something similar to be available.

Until you have something more palpable than belief, "let the others
extend it when they really need it." as I already mentioned.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
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  reply	other threads:[~2020-12-09 12:54 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-07 23:10 [PATCH v8] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests Ashish Kalra
2020-12-08 22:22 ` Konrad Rzeszutek Wilk
2020-12-08 23:01   ` Borislav Petkov
2020-12-08 23:27     ` Konrad Rzeszutek Wilk
2020-12-08 23:33       ` Borislav Petkov
2020-12-09 11:01 ` Borislav Petkov
2020-12-09 12:29   ` Ashish Kalra
2020-12-09 12:54     ` Borislav Petkov [this message]
2020-12-09 13:19       ` Ashish Kalra
2020-12-09 17:51         ` Borislav Petkov
2020-12-09 19:34           ` Ashish Kalra
2020-12-09 19:43             ` Borislav Petkov

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