netdev - RE: [PATCH] [net-next] net: hns3: add IOMMU

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Message-ID: <96df804b6d9d467391fda27d90b5227c@huawei.com>
Date: Mon, 4 Nov 2024 10:40:49 +0000
From: Salil Mehta <salil.mehta@...wei.com>
To: Robin Murphy <robin.murphy@....com>, Arnd Bergmann <arnd@...nel.org>,
	"shenjian (K)" <shenjian15@...wei.com>
CC: Arnd Bergmann <arnd@...db.de>, Will Deacon <will@...nel.org>, Joerg Roedel
	<jroedel@...e.de>, "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, "Andrew
 Lunn" <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, shaojijie <shaojijie@...wei.com>, wangpeiyang
	<wangpeiyang1@...wei.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] [net-next] net: hns3: add IOMMU_SUPPORT dependency

HI Robin,

>  From: Robin Murphy <robin.murphy@....com>
>  Sent: Monday, November 4, 2024 10:29 AM
>  To: Arnd Bergmann <arnd@...nel.org>; shenjian (K)
>  <shenjian15@...wei.com>; Salil Mehta <salil.mehta@...wei.com>
>  Cc: Arnd Bergmann <arnd@...db.de>; Will Deacon <will@...nel.org>;
>  Joerg Roedel <jroedel@...e.de>; iommu@...ts.linux.dev; Andrew Lunn
>  <andrew+netdev@...n.ch>; David S. Miller <davem@...emloft.net>; Eric
>  Dumazet <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>;
>  Paolo Abeni <pabeni@...hat.com>; shaojijie <shaojijie@...wei.com>;
>  wangpeiyang <wangpeiyang1@...wei.com>; netdev@...r.kernel.org;
>  linux-kernel@...r.kernel.org
>  Subject: Re: [PATCH] [net-next] net: hns3: add IOMMU_SUPPORT
>  dependency
>  
>  On 2024-11-04 8:21 am, Arnd Bergmann wrote:
>  > From: Arnd Bergmann <arnd@...db.de>
>  >
>  > The hns3 driver started filling iommu_iotlb_gather structures itself,
>  > which requires CONFIG_IOMMU_SUPPORT is enabled:
>  >
>  > drivers/net/ethernet/hisilicon/hns3/hns3_enet.c: In function
>  'hns3_dma_map_sync':
>  > drivers/net/ethernet/hisilicon/hns3/hns3_enet.c:395:14: error: 'struct
>  iommu_iotlb_gather' has no member named 'start'
>  >    395 |  iotlb_gather.start = iova;
>  >        |              ^
>  > drivers/net/ethernet/hisilicon/hns3/hns3_enet.c:396:14: error: 'struct
>  iommu_iotlb_gather' has no member named 'end'
>  >    396 |  iotlb_gather.end = iova + granule - 1;
>  >        |              ^
>  > drivers/net/ethernet/hisilicon/hns3/hns3_enet.c:397:14: error: 'struct
>  iommu_iotlb_gather' has no member named 'pgsize'
>  >    397 |  iotlb_gather.pgsize = granule;
>  >        |              ^
>  >
>  > Add a Kconfig dependency to make it build in random configurations.
>  >
>  > Cc: Will Deacon <will@...nel.org>
>  > Cc: Joerg Roedel <jroedel@...e.de>
>  > Cc: Robin Murphy <robin.murphy@....com>
>  > Cc: iommu@...ts.linux.dev
>  > Fixes: f2c14899caba ("net: hns3: add sync command to sync io-pgtable")
>  > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>  > ---
>  > I noticed that no other driver does this, so it would be good to have
>  > a confirmation from the iommu maintainers that this is how the
>  > interface and the dependency is intended to be used.
>  
>  WTF is that patch doing!? No, random device drivers should absolutely not
>  be poking into IOMMU driver internals, this is egregiously wrong and the
>  correct action is to drop it entirely.


Absolutely agree with it. Sorry I haven't been in touch for quite some time. Let
me catch the whole story.  Feel free to drop this patch.

Thanks
Salil.

>  
>  Thanks,
>  Robin.
>  
>  > ---
>  >   drivers/net/ethernet/hisilicon/Kconfig | 1 +
>  >   1 file changed, 1 insertion(+)
>  >
>  > diff --git a/drivers/net/ethernet/hisilicon/Kconfig
>  > b/drivers/net/ethernet/hisilicon/Kconfig
>  > index 65302c41bfb1..790efc8d2de6 100644
>  > --- a/drivers/net/ethernet/hisilicon/Kconfig
>  > +++ b/drivers/net/ethernet/hisilicon/Kconfig
>  > @@ -91,6 +91,7 @@ config HNS_ENET
>  >   config HNS3
>  >   	tristate "Hisilicon Network Subsystem Support HNS3 (Framework)"
>  >   	depends on PCI
>  > +	depends on IOMMU_SUPPORT
>  >   	select NET_DEVLINK
>  >   	select PAGE_POOL
>  >   	help
>