linux-kernel - Re: [PATCH v6 0/7] Fix stale IOTLB entries for kernel address space

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Message-ID: <16775184-a98b-40dc-8fb7-168f90edb427@linux.intel.com>
Date: Wed, 22 Oct 2025 13:06:58 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>,
 Dave Hansen <dave.hansen@...el.com>, Jason Gunthorpe <jgg@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Joerg Roedel
 <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>, Kevin Tian <kevin.tian@...el.com>,
 Jann Horn <jannh@...gle.com>, Vasant Hegde <vasant.hegde@....com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Alistair Popple <apopple@...dia.com>,
 Peter Zijlstra <peterz@...radead.org>, Uladzislau Rezki <urezki@...il.com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Andy Lutomirski <luto@...nel.org>, Yi Lai <yi1.lai@...el.com>,
 David Hildenbrand <david@...hat.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Michal Hocko <mhocko@...nel.org>, Matthew Wilcox <willy@...radead.org>,
 iommu@...ts.linux.dev, security@...nel.org, x86@...nel.org,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 "Jiang, Dave" <dave.jiang@...el.com>
Subject: Re: [PATCH v6 0/7] Fix stale IOTLB entries for kernel address space

On 10/18/25 02:26, Vinicius Costa Gomes wrote:
> Dave Hansen<dave.hansen@...el.com> writes:
> 
>> On 10/17/25 07:01, Jason Gunthorpe wrote:
>>>>> The other alternative is to have arch_vmap_pmd_supported() return false
>>>>> when SVA is active, or maybe when it's supported on the platform.
>>>>>
>>>>> Either of those are 10-ish lines of code and easy to backport.
>>>> Hi iommu folks, any insights on this?
>>> IDK, the only SVA user on x86 I know is IDXD, so if you do the above
>>> plan you break IDXD in all stable kernels. Doesn't sound OK?
>> Vinicius, any thoughts on this?
>>
> This won't break IDXD exactly/totally, it would cause it to be
> impossible for users to create shared DSA/IAA workqueues (which are the
> nicer ones to use), and it will cause the driver to print some not happy
> messages in the kernel logs. The in-kernel users of IDXD (iaa_crypto for
> zswap, for example) will continue to work.
> 
> In short, I am not happy, but I think it's workable, even better if
> there are alternatives in case people complain.

Okay, so I will add an extra patch to disable SVA for x86 arch and re-
enable it after the kernel page table free callback is done.

Thanks,
baolu