From: Joerg Roedel <joro@8bytes.org>
To: Konrad Rzeszutek Wilk <konrad@darnok.org>
Cc: will@kernel.org,
"open list:AMD IOMMU \(AMD-VI\)"
<iommu@lists.linux-foundation.org>,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
Robin Murphy <robin.murphy@arm.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iommu/amd: Enable swiotlb if any device supports iommu v2 and uses identity mapping
Date: Wed, 14 Jul 2021 12:25:31 +0200 [thread overview]
Message-ID: <YO67m/jaBvco+I36@8bytes.org> (raw)
In-Reply-To: <YO4odF0EwqxfNLFq@fedora>
On Tue, Jul 13, 2021 at 07:57:40PM -0400, Konrad Rzeszutek Wilk wrote:
> The SWIOTLB does have support to do late initialization (xen-pcifront
> does that for example - so if you add devices that can't do 64-bit it
> will allocate something like 4MB).
That sounds like a way to evaluate. I suggest to allocate the SWIOTLB
memory at boot and when the IOMMUs are initialized we re-evaluate what
we ended up with and free the SWIOTLB memory if its not needed.
If that turns out to be wrong during runtime (e.g. because a device is
switched to a passthrough default domain at runtime), we allocate a
small aperture for this device like the above mentioned 4MB.
(A boot option to always keep the aperture around might also be helpful
for some setups)
Regards,
Joerg
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next prev parent reply other threads:[~2021-07-14 10:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-08 7:42 [PATCH] iommu/amd: Enable swiotlb if any device supports iommu v2 and uses identity mapping Kai-Heng Feng
2021-07-08 9:28 ` Joerg Roedel
2021-07-08 10:18 ` Robin Murphy
2021-07-08 13:57 ` Kai-Heng Feng
2021-07-08 14:43 ` Robin Murphy
2021-07-13 23:57 ` Konrad Rzeszutek Wilk
2021-07-14 4:59 ` Kai-Heng Feng
2021-07-14 10:25 ` Joerg Roedel [this message]
2021-09-09 6:32 ` Kai-Heng Feng
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