From: Kai-Heng Feng <kai.heng.feng@canonical.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>,
Robin Murphy <robin.murphy@arm.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: Thu, 9 Sep 2021 14:32:55 +0800 [thread overview]
Message-ID: <CAAd53p4138BB_5-++0P9k91B1dCuKzuv1yGjiG77ewhd1MRSbQ@mail.gmail.com> (raw)
In-Reply-To: <YO67m/jaBvco+I36@8bytes.org>
On Wed, Jul 14, 2021 at 6:25 PM Joerg Roedel <joro@8bytes.org> wrote:
>
> 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.
I am currently working on this but I found that 4MB is not enough,
16MB is the minimal size to make the device work.
How do I know the right SWIOTLB size for each device?
>
> (A boot option to always keep the aperture around might also be helpful
> for some setups)
OK, will also implement this in next iteration.
Kai-Heng
>
> Regards,
>
> Joerg
prev parent reply other threads:[~2021-09-09 6:52 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
2021-09-09 6:32 ` Kai-Heng Feng [this message]
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