From: Joerg Roedel <joro@8bytes.org>
To: Konrad Rzeszutek Wilk <konrad@darnok.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
will@kernel.org,
"open list:AMD IOMMU (AMD-VI)" <iommu@lists.linux-foundation.org>,
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
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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