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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

WARNING: multiple messages have this Message-ID (diff)
From: Kai-Heng Feng <kai.heng.feng@canonical.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>,
	"open list:AMD IOMMU \(AMD-VI\)"
	<iommu@lists.linux-foundation.org>,
	Robin Murphy <robin.murphy@arm.com>,
	open list <linux-kernel@vger.kernel.org>,
	will@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
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2021-09-09  6:52 UTC|newest]

Thread overview: 18+ 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  7:42 ` Kai-Heng Feng
2021-07-08  9:28 ` Joerg Roedel
2021-07-08  9:28   ` Joerg Roedel
2021-07-08 10:18   ` Robin Murphy
2021-07-08 10:18     ` Robin Murphy
2021-07-08 13:57     ` Kai-Heng Feng
2021-07-08 13:57       ` Kai-Heng Feng
2021-07-08 14:43       ` Robin Murphy
2021-07-08 14:43         ` Robin Murphy
2021-07-13 23:57         ` Konrad Rzeszutek Wilk
2021-07-13 23:57           ` Konrad Rzeszutek Wilk
2021-07-14  4:59           ` Kai-Heng Feng
2021-07-14  4:59             ` Kai-Heng Feng
2021-07-14 10:25           ` Joerg Roedel
2021-07-14 10:25             ` Joerg Roedel
2021-09-09  6:32             ` Kai-Heng Feng [this message]
2021-09-09  6:32               ` Kai-Heng Feng

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