linux-kernel - Re: [PATCH v2 0/2] iommu/amd: Don't use atomic64_t for domain->pt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 26 Jun 2020 08:30:21 -0400
From:   Qian Cai <cai@....pw>
To:     Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v2 0/2] iommu/amd: Don't use atomic64_t for domain->pt_root

> On Jun 26, 2020, at 4:05 AM, Joerg Roedel <joro@...tes.org> wrote:
> 
> a previous discussion pointed out that using atomic64_t for that
> purpose is a bit of overkill. This patch-set replaces it with unsigned
> long and introduces some helpers first to make the change more easy.

BTW, from the previous discussion, Linus mentioned,

“
The thing is, the 64-bit atomic reads/writes are very expensive on
32-bit x86. If it was just a native pointer, it would be much cheaper
than an "atomic64_t".
“

However, here we have AMD_IOMMU depend on x86_64, so I am wondering if it makes any sense to run this code on 32-bit x86 at all?