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From: Qian Cai <>
To: Joerg Roedel <>
Cc:, Joerg Roedel <>,
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: <> (raw)
In-Reply-To: <>

> On Jun 26, 2020, at 4:05 AM, Joerg Roedel <> 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?
iommu mailing list

  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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