From: "Christian König" <christian.koenig@amd.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, Logan Gunthorpe <logang@deltatee.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mm@kvack.org, iommu@lists.linux-foundation.org,
Stephen Bates <sbates@raithlin.com>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>,
Ira Weiny <iweiny@intel.com>, John Hubbard <jhubbard@nvidia.com>,
Don Dutile <ddutile@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Daniel Vetter <daniel.vetter@ffwll.ch>,
Jakowski Andrzej <andrzej.jakowski@intel.com>,
Minturn Dave B <dave.b.minturn@intel.com>,
Jason Ekstrand <jason@jlekstrand.net>,
Dave Hansen <dave.hansen@linux.intel.com>,
Xiong Jianxin <jianxin.xiong@intel.com>
Subject: Re: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
Date: Wed, 24 Mar 2021 19:34:53 +0100 [thread overview]
Message-ID: <044e4f2b-6cb9-7740-622c-ec807bb1a79b@amd.com> (raw)
In-Reply-To: <20210324172157.GH2710221@ziepe.ca>
Am 24.03.21 um 18:21 schrieb Jason Gunthorpe:
> On Mon, Mar 15, 2021 at 10:27:08AM -0600, Logan Gunthorpe wrote:
>
>> In this case the WARN_ON is just to guard against misuse of the
>> function. It should never happen unless a developer changes the code in
>> a way that is incorrect. So I think that's the correct use of WARN_ON.
>> Though I might change it to WARN and return, that seems safer.
> Right, WARN_ON and return is the right pattern for an assertion that
> must never happen:
>
> if (WARN_ON(foo))
> return -1
>
> Linus wants assertions like this to be able to recover. People runing
> the 'panic on warn' mode want the kernel to stop if it detects an
> internal malfunction.
The only justification I can see for a "panic on warn" is to prevent
further data loss or warn early about a crash.
We only use a BUG_ON() when the alternative would be to corrupt something.
Christian.
>
> Jason
WARNING: multiple messages have this Message-ID (diff)
From: "Christian König" <christian.koenig@amd.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, Logan Gunthorpe <logang@deltatee.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mm@kvack.org, iommu@lists.linux-foundation.org,
Stephen Bates <sbates@raithlin.com>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>,
Ira Weiny <iweiny@intel.com>, John Hubbard <jhubbard@nvidia.com>,
Don Dutile <ddutile@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Daniel Vetter <daniel.vetter@ffwll.ch>,
Jakowski Andrzej <andrzej.jakowski@intel.com>,
Minturn Dave B <dave.b.minturn@intel.com>,
Jason Ekstrand <jason@jlekstrand.net>,
Dave Hansen <dave.hansen@linux.intel.com>,
Xiong Jianxin <jianxin.xiong@intel.com>
Subject: Re: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
Date: Wed, 24 Mar 2021 19:34:53 +0100 [thread overview]
Message-ID: <044e4f2b-6cb9-7740-622c-ec807bb1a79b@amd.com> (raw)
In-Reply-To: <20210324172157.GH2710221@ziepe.ca>
Am 24.03.21 um 18:21 schrieb Jason Gunthorpe:
> On Mon, Mar 15, 2021 at 10:27:08AM -0600, Logan Gunthorpe wrote:
>
>> In this case the WARN_ON is just to guard against misuse of the
>> function. It should never happen unless a developer changes the code in
>> a way that is incorrect. So I think that's the correct use of WARN_ON.
>> Though I might change it to WARN and return, that seems safer.
> Right, WARN_ON and return is the right pattern for an assertion that
> must never happen:
>
> if (WARN_ON(foo))
> return -1
>
> Linus wants assertions like this to be able to recover. People runing
> the 'panic on warn' mode want the kernel to stop if it detects an
> internal malfunction.
The only justification I can see for a "panic on warn" is to prevent
further data loss or warn early about a crash.
We only use a BUG_ON() when the alternative would be to corrupt something.
Christian.
>
> Jason
_______________________________________________
Linux-nvme mailing list
Linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme
WARNING: multiple messages have this Message-ID (diff)
From: "Christian König" <christian.koenig@amd.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, Logan Gunthorpe <logang@deltatee.com>
Cc: Minturn Dave B <dave.b.minturn@intel.com>,
Jakowski Andrzej <andrzej.jakowski@intel.com>,
linux-pci@vger.kernel.org, Daniel Vetter <daniel.vetter@ffwll.ch>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ira Weiny <iweiny@intel.com>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
Stephen Bates <sbates@raithlin.com>,
linux-block@vger.kernel.org, linux-mm@kvack.org,
iommu@lists.linux-foundation.org,
Matthew Wilcox <willy@infradead.org>,
Jason Ekstrand <jason@jlekstrand.net>,
John Hubbard <jhubbard@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
Ira Weiny <ira.weiny@intel.com>, Christoph Hellwig <hch@lst.de>,
Xiong Jianxin <jianxin.xiong@intel.com>
Subject: Re: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
Date: Wed, 24 Mar 2021 19:34:53 +0100 [thread overview]
Message-ID: <044e4f2b-6cb9-7740-622c-ec807bb1a79b@amd.com> (raw)
In-Reply-To: <20210324172157.GH2710221@ziepe.ca>
Am 24.03.21 um 18:21 schrieb Jason Gunthorpe:
> On Mon, Mar 15, 2021 at 10:27:08AM -0600, Logan Gunthorpe wrote:
>
>> In this case the WARN_ON is just to guard against misuse of the
>> function. It should never happen unless a developer changes the code in
>> a way that is incorrect. So I think that's the correct use of WARN_ON.
>> Though I might change it to WARN and return, that seems safer.
> Right, WARN_ON and return is the right pattern for an assertion that
> must never happen:
>
> if (WARN_ON(foo))
> return -1
>
> Linus wants assertions like this to be able to recover. People runing
> the 'panic on warn' mode want the kernel to stop if it detects an
> internal malfunction.
The only justification I can see for a "panic on warn" is to prevent
further data loss or warn early about a crash.
We only use a BUG_ON() when the alternative would be to corrupt something.
Christian.
>
> Jason
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-03-24 18:35 UTC|newest]
Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 23:31 [RFC PATCH v2 00/11] Add support to dma_map_sg for P2PDMA Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 01/11] PCI/P2PDMA: Pass gfp_mask flags to upstream_bridge_distance_warn() Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-12 20:39 ` Bjorn Helgaas
2021-03-12 20:39 ` Bjorn Helgaas
2021-03-12 20:39 ` Bjorn Helgaas
2021-03-12 20:53 ` Logan Gunthorpe
2021-03-12 20:53 ` Logan Gunthorpe
2021-03-12 20:53 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 02/11] PCI/P2PDMA: Avoid pci_get_slot() which sleeps Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-12 20:57 ` Bjorn Helgaas
2021-03-12 20:57 ` Bjorn Helgaas
2021-03-12 20:57 ` Bjorn Helgaas
2021-03-12 21:37 ` Logan Gunthorpe
2021-03-12 21:37 ` Logan Gunthorpe
2021-03-12 21:37 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 03/11] PCI/P2PDMA: Attempt to set map_type if it has not been set Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset() Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-13 1:38 ` Ira Weiny
2021-03-13 1:38 ` Ira Weiny
2021-03-13 1:38 ` Ira Weiny
2021-03-15 16:27 ` Logan Gunthorpe
2021-03-15 16:27 ` Logan Gunthorpe
2021-03-15 16:27 ` Logan Gunthorpe
2021-03-24 17:21 ` Jason Gunthorpe
2021-03-24 17:21 ` Jason Gunthorpe
2021-03-24 17:21 ` Jason Gunthorpe
2021-03-24 18:34 ` Christian König [this message]
2021-03-24 18:34 ` Christian König
2021-03-24 18:34 ` Christian König
2021-03-13 2:32 ` Ira Weiny
2021-03-13 2:32 ` Ira Weiny
2021-03-13 2:32 ` Ira Weiny
2021-03-15 16:30 ` Logan Gunthorpe
2021-03-15 16:30 ` Logan Gunthorpe
2021-03-15 16:30 ` Logan Gunthorpe
2021-03-16 8:14 ` Christoph Hellwig
2021-03-16 8:14 ` Christoph Hellwig
2021-03-16 8:14 ` Christoph Hellwig
2021-03-11 23:31 ` [RFC PATCH v2 05/11] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 06/11] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-12 15:52 ` Robin Murphy
2021-03-12 15:52 ` Robin Murphy
2021-03-12 15:52 ` Robin Murphy
2021-03-12 16:24 ` Logan Gunthorpe
2021-03-12 16:24 ` Logan Gunthorpe
2021-03-12 16:24 ` Logan Gunthorpe
2021-03-12 18:11 ` Robin Murphy
2021-03-12 18:11 ` Robin Murphy
2021-03-12 18:11 ` Robin Murphy
2021-03-12 18:27 ` Logan Gunthorpe
2021-03-12 18:27 ` Logan Gunthorpe
2021-03-12 18:27 ` Logan Gunthorpe
2021-03-16 7:58 ` Christoph Hellwig
2021-03-16 7:58 ` Christoph Hellwig
2021-03-16 7:58 ` Christoph Hellwig
2021-03-16 15:54 ` Logan Gunthorpe
2021-03-16 15:54 ` Logan Gunthorpe
2021-03-16 15:54 ` Logan Gunthorpe
2021-03-16 7:56 ` Christoph Hellwig
2021-03-16 7:56 ` Christoph Hellwig
2021-03-16 7:56 ` Christoph Hellwig
2021-03-16 8:11 ` Christoph Hellwig
2021-03-16 8:11 ` Christoph Hellwig
2021-03-16 8:11 ` Christoph Hellwig
2021-03-11 23:31 ` [RFC PATCH v2 07/11] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-13 2:36 ` Ira Weiny
2021-03-13 2:36 ` Ira Weiny
2021-03-13 2:36 ` Ira Weiny
2021-03-15 16:33 ` Logan Gunthorpe
2021-03-15 16:33 ` Logan Gunthorpe
2021-03-15 16:33 ` Logan Gunthorpe
2021-03-16 8:00 ` Christoph Hellwig
2021-03-16 8:00 ` Christoph Hellwig
2021-03-16 8:00 ` Christoph Hellwig
2021-03-16 8:15 ` Christoph Hellwig
2021-03-16 8:15 ` Christoph Hellwig
2021-03-16 8:15 ` Christoph Hellwig
2021-03-11 23:31 ` [RFC PATCH v2 08/11] iommu/dma: Support PCI P2PDMA pages in dma-iommu map_sg Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-12 15:52 ` Robin Murphy
2021-03-12 15:52 ` Robin Murphy
2021-03-12 15:52 ` Robin Murphy
2021-03-12 17:03 ` Logan Gunthorpe
2021-03-12 17:03 ` Logan Gunthorpe
2021-03-12 17:03 ` Logan Gunthorpe
2021-03-12 19:47 ` Robin Murphy
2021-03-12 19:47 ` Robin Murphy
2021-03-12 19:47 ` Robin Murphy
2021-03-12 20:06 ` Logan Gunthorpe
2021-03-12 20:06 ` Logan Gunthorpe
2021-03-12 20:06 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 09/11] block: Add BLK_STS_P2PDMA Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-16 8:00 ` Christoph Hellwig
2021-03-16 8:00 ` Christoph Hellwig
2021-03-16 8:00 ` Christoph Hellwig
2021-03-16 16:02 ` Logan Gunthorpe
2021-03-16 16:02 ` Logan Gunthorpe
2021-03-16 16:02 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 10/11] nvme-pci: Check DMA ops when indicating support for PCI P2PDMA Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` [RFC PATCH v2 11/11] nvme-pci: Convert to using dma_map_sg for p2pdma pages Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:31 ` Logan Gunthorpe
2021-03-11 23:59 ` Jason Gunthorpe
2021-03-11 23:59 ` Jason Gunthorpe
2021-03-11 23:59 ` Jason Gunthorpe
2021-03-12 1:37 ` Logan Gunthorpe
2021-03-12 1:37 ` Logan Gunthorpe
2021-03-12 1:37 ` Logan Gunthorpe
2021-03-12 15:51 ` [RFC PATCH v2 00/11] Add support to dma_map_sg for P2PDMA Robin Murphy
2021-03-12 15:51 ` Robin Murphy
2021-03-12 15:51 ` Robin Murphy
2021-03-12 16:18 ` Logan Gunthorpe
2021-03-12 16:18 ` Logan Gunthorpe
2021-03-12 16:18 ` Logan Gunthorpe
2021-03-12 17:46 ` Robin Murphy
2021-03-12 17:46 ` Robin Murphy
2021-03-12 17:46 ` Robin Murphy
2021-03-12 18:24 ` Logan Gunthorpe
2021-03-12 18:24 ` Logan Gunthorpe
2021-03-12 18:24 ` Logan Gunthorpe
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