From: Qian Cai <cai@lca.pw>
To: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org, Joerg Roedel <jroedel@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/2] iommu/amd: Don't use atomic64_t for domain->pt_root
Date: Fri, 26 Jun 2020 08:30:21 -0400 [thread overview]
Message-ID: <63D91069-6A2E-4C05-8409-76A56D1E0FCA@lca.pw> (raw)
In-Reply-To: <20200626080547.24865-1-joro@8bytes.org>
> On Jun 26, 2020, at 4:05 AM, Joerg Roedel <joro@8bytes.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?
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next prev parent reply other threads:[~2020-06-26 12:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-26 8:05 [PATCH v2 0/2] iommu/amd: Don't use atomic64_t for domain->pt_root Joerg Roedel
2020-06-26 8:05 ` [PATCH v2 1/2] iommu/amd: Add helper functions to update domain->pt_root Joerg Roedel
2020-06-26 8:05 ` [PATCH v2 2/2] iommu/amd: Use 'unsigned long' for domain->pt_root Joerg Roedel
2020-06-26 12:30 ` Qian Cai [this message]
2020-06-30 9:57 ` [PATCH v2 0/2] iommu/amd: Don't use atomic64_t " Joerg Roedel
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