From: Qian Cai <cai@lca.pw>
To: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] iommu/amd: fix a race in fetch_pte()
Date: Sat, 18 Apr 2020 09:01:35 -0400 [thread overview]
Message-ID: <57CBF6B2-4745-4E36-9AA5-7E0876E3DA8F@lca.pw> (raw)
In-Reply-To: <20200418121022.GA6113@8bytes.org>
> On Apr 18, 2020, at 8:10 AM, Joerg Roedel <joro@8bytes.org> wrote:
>
> Yes, your patch still looks racy. You need to atomically read
> domain->pt_root to a stack variable and derive the pt_root pointer and
> the mode from that variable instead of domain->pt_root directly. If you
> read the domain->pt_root twice there could still be an update between
> the two reads.
> Probably the lock in increase_address_space() can also be avoided if
> pt_root is updated using cmpxchg()?
Hard to tell without testing further. I’ll leave that optimization in the future, and focus on fixing those races first.
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next prev parent reply other threads:[~2020-04-18 13:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 2:12 [RFC PATCH] iommu/amd: fix a race in fetch_pte() Qian Cai
2020-04-07 15:36 ` Qian Cai
2020-04-08 14:19 ` Joerg Roedel
2020-04-14 1:36 ` Qian Cai
2020-04-17 1:42 ` Qian Cai
2020-04-18 12:10 ` Joerg Roedel
2020-04-18 13:01 ` Qian Cai [this message]
2020-04-18 18:34 ` Joerg Roedel
2020-04-20 2:07 ` Qian Cai
2020-04-20 13:26 ` Qian Cai
2020-04-29 8:47 ` Joerg Roedel
2020-04-29 11:20 ` Joerg Roedel
2020-04-30 1:04 ` Qian Cai
2020-05-03 13:04 ` Qian Cai
2020-05-03 18:39 ` Joerg Roedel
2020-05-03 19:12 ` Qian Cai
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