linux-kernel - Re: [PATCH 2/4] swiotlb: Add a new cc-swiotlb implementation for Confidential VMs

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Message-ID: <ee5d8c26-a453-678c-be48-d586271573d6@linux.intel.com>
Date:   Tue, 31 Jan 2023 09:16:11 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Guorui Yu <GuoRui.Yu@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        konrad.wilk@...cle.com, linux-coco@...ts.linux.dev
Cc:     robin.murphy@....com
Subject: Re: [PATCH 2/4] swiotlb: Add a new cc-swiotlb implementation for
 Confidential VMs

 >No, this cannot guarantee we always have sufficient TLB caches, so we 
can also have a "No memory for cc-swiotlb buffer" warning.

It's not just a warning, it will be IO errors, right?

>
> But I want to emphasize that in this case, the current implementation 
> is no worse than the legacy implementation. Moreover, dynamic TLB 
> allocation is more suitable for situations where more disks/network 
> devices will be hotplugged, in which case you cannot pre-set a 
> reasonable value.

That's a reasonable stand point, but have to emphasize that is 
"probabilistic" in all the descriptions and comments.

I assume you did some stress testing (E.g. all cores submitting at full 
bandwidth) to validate that it works for you?

-Andi