linux-kernel - Re: [PATCH v2] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests.

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Message-ID: <20200312004302.GB26448@ashkalra_ubuntu_server>
Date:   Thu, 12 Mar 2020 00:43:02 +0000
From:   Ashish Kalra <ashish.kalra@....com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     Konrad Rzeszutek Wilk <konrad@...nok.org>, hch@....de,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, luto@...nel.org, peterz@...radead.org,
        dave.hansen@...ux-intel.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, brijesh.singh@....com,
        Thomas.Lendacky@....com
Subject: Re: [PATCH v2] swiotlb: Adjust SWIOTBL bounce buffer size for SEV
 guests.

On Tue, Mar 03, 2020 at 12:03:53PM -0500, Konrad Rzeszutek Wilk wrote:
> > > 
> > > >> 
> > > >>    Actually you seem to be piggybacking on pci_swiotlb_detect_4gb - so
> > > >>    perhaps add in this code ? Albeit it really should be in it's own
> > > >>    file, not in arch/x86/kernel/pci-swiotlb.c
> > > 
> > > Actually, we piggyback on pci_swiotlb_detect_override which sets
> > > swiotlb=1 as x86_64_start_kernel() and invocation of sme_early_init()
> > > forces swiotlb on, but again this is all x86 architecture specific.
> 
> Then it looks like the best bet is to do it from within swiotlb_init?
> We really can't do it from swiotlb_size_or_default - that function
> should just return a value and nothing else.

Ok, i will fix this patch accordingly and resubmit it.

Thanks,
Ashish