RE: [PATCH] [net-next] net: hns3: add IOMMU_SUPPORT dependency

[Salil Mehta <salil.mehta@huawei.com>]

>  From: Salil Mehta <salil.mehta@huawei.com>
>  Sent: Monday, November 4, 2024 10:41 AM
>  To: Robin Murphy <robin.murphy@arm.com>; Arnd Bergmann
>  <arnd@kernel.org>; shenjian (K) <shenjian15@huawei.com>
>  
>  HI Robin,
>  
>  >  From: Robin Murphy <robin.murphy@arm.com>
>  >  Sent: Monday, November 4, 2024 10:29 AM
>  >  To: Arnd Bergmann <arnd@kernel.org>; shenjian (K)
>  > <shenjian15@huawei.com>; Salil Mehta <salil.mehta@huawei.com>
>  >  Cc: Arnd Bergmann <arnd@arndb.de>; Will Deacon <will@kernel.org>;
>  > Joerg Roedel <jroedel@suse.de>; iommu@lists.linux.dev; Andrew Lunn
>  > <andrew+netdev@lunn.ch>; David S. Miller <davem@davemloft.net>;
>  Eric
>  > Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>;
>  > Paolo Abeni <pabeni@redhat.com>; shaojijie <shaojijie@huawei.com>;
>  > wangpeiyang <wangpeiyang1@huawei.com>; netdev@vger.kernel.org;
>  > linux-kernel@vger.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@arndb.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@kernel.org>
>  >  > Cc: Joerg Roedel <jroedel@suse.de>
>  >  > Cc: Robin Murphy <robin.murphy@arm.com>  > Cc:
>  > iommu@lists.linux.dev  > Fixes: f2c14899caba ("net: hns3: add sync
>  > command to sync io-pgtable")  > Signed-off-by: Arnd Bergmann
>  > <arnd@arndb.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.


Just to make it clear I meant the culprit patch:
https://lore.kernel.org/netdev/20241025092938.2912958-3-shaojijie@huawei.com/


>  
>  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
>  >