Message-ID: <ee5d8c26-a453-678c-be48-d586271573d6@linux.intel.com>
Date:   Tue, 31 Jan 2023 09:16:11 -0800
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Subject: Re: [PATCH 2/4] swiotlb: Add a new cc-swiotlb implementation for
 Confidential VMs
To:     Guorui Yu <GuoRui.Yu@linux.alibaba.com>,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
        konrad.wilk@oracle.com, linux-coco@lists.linux.dev
Cc:     robin.murphy@arm.com
References: <20230128083254.86012-1-GuoRui.Yu@linux.alibaba.com>
 <20230128083254.86012-3-GuoRui.Yu@linux.alibaba.com>
 <9b167caf-1b10-f97a-d96a-b7ead8e785e8@linux.intel.com>
 <2ec59355-c8d5-c794-16e8-7d646b43c455@linux.alibaba.com>
 <09a56915-7ce2-b70c-33ec-3a8767269637@linux.intel.com>
 <ccc21265-07aa-cd82-f679-4fee9c51df47@linux.alibaba.com>
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From:   Andi Kleen <ak@linux.intel.com>
In-Reply-To: <ccc21265-07aa-cd82-f679-4fee9c51df47@linux.alibaba.com>
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 >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