From: Robin Murphy <robin.murphy@arm.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
iommu@lists.linux.dev, Maxime Ripard <maxime@cerno.tech>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel@lists.infradead.org,
linux-sunxi@lists.linux.dev, Samuel Holland <samuel@sholland.org>,
Chen-Yu Tsai <wens@csie.org>, Will Deacon <will@kernel.org>
Cc: Joerg Roedel <jroedel@suse.de>, Andre Przywara <andre.przywara@arm.com>
Subject: Re: [PATCH] iommu/sun50i: Remove IOMMU_DOMAIN_IDENTITY
Date: Mon, 28 Nov 2022 14:21:56 +0000 [thread overview]
Message-ID: <a4f7157f-bd1d-ed7e-161f-e39c8c940a02@arm.com> (raw)
In-Reply-To: <0-v1-97f0adf27b5e+1f0-s50_identity_jgg@nvidia.com>
On 2022-11-28 14:06, Jason Gunthorpe wrote:
> This driver treats IOMMU_DOMAIN_IDENTITY the same as UNMANAGED, which
> cannot possibly be correct.
>
> UNMANAGED domains are required to start out blocking all DMAs. This seems
> to be what this driver does as it allocates a first level 'dt' for the IO
> page table that is 0 filled.
>
> Thus UNMANAGED looks like a working IO page table, and so IDENTITY must be
> a mistake. Remove it.
Ah yes, this did once catch my eye ages ago and Andre confirmed that
real hardware fell over with "iommu.passthrough=1", but it seems we both
forgot about it again before a patch got written. Thanks for taking the
time!
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
> drivers/iommu/sun50i-iommu.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index cd9b74ee24def1..0843418434ff3a 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -601,7 +601,6 @@ static struct iommu_domain *sun50i_iommu_domain_alloc(unsigned type)
> struct sun50i_iommu_domain *sun50i_domain;
>
> if (type != IOMMU_DOMAIN_DMA &&
> - type != IOMMU_DOMAIN_IDENTITY &&
> type != IOMMU_DOMAIN_UNMANAGED)
> return NULL;
>
>
> base-commit: 328827239b9ce3a95b5c0d33e8875651580de053
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next prev parent reply other threads:[~2022-11-28 14:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-28 14:06 [PATCH] iommu/sun50i: Remove IOMMU_DOMAIN_IDENTITY Jason Gunthorpe
2022-11-28 14:21 ` Robin Murphy [this message]
2022-12-05 10:53 ` Joerg Roedel
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