iommu.lists.linux-foundation.org archive mirror
 help / color / mirror / Atom feed
From: Logan Gunthorpe <logang@deltatee.com>
To: James Sewart <jamessewart@arista.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	Dmitry Safonov <dima@arista.com>,
	linux-pci@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	Bjorn Helgaas <helgaas@kernel.org>
Subject: Re: [PATCH v4 1/2] PCI: Add parameter nr_devfns to pci_add_dma_alias
Date: Fri, 29 Nov 2019 10:26:57 -0700	[thread overview]
Message-ID: <d811576e-0f89-2303-a554-2701af5c5647@deltatee.com> (raw)
In-Reply-To: <F26CC19F-66C2-466B-AE30-D65E10BA3022@arista.com>



On 2019-11-29 10:19 a.m., James Sewart wrote:
> 
> 
>> On 29 Nov 2019, at 16:50, Logan Gunthorpe <logang@deltatee.com> wrote:
>>
>>
>>
>> On 2019-11-29 5:49 a.m., James Sewart wrote:
>>> pci_add_dma_alias can now be used to create a dma alias for a range of
>>> devfns.
>>>
>>> Signed-off-by: James Sewart <jamessewart@arista.com>
>>> ---
>>> drivers/pci/pci.c    | 23 ++++++++++++++++++-----
>>> drivers/pci/quirks.c | 14 +++++++-------
>>> include/linux/pci.h  |  2 +-
>>> 3 files changed, 26 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>>> index a97e2571a527..9b0e3481fe17 100644
>>> --- a/drivers/pci/pci.c
>>> +++ b/drivers/pci/pci.c
>>> @@ -5857,7 +5857,8 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
>>> /**
>>>  * pci_add_dma_alias - Add a DMA devfn alias for a device
>>>  * @dev: the PCI device for which alias is added
>>> - * @devfn: alias slot and function
>>> + * @devfn_from: alias slot and function
>>> + * @nr_devfns: Number of subsequent devfns to alias
>>>  *
>>>  * This helper encodes an 8-bit devfn as a bit number in dma_alias_mask
>>>  * which is used to program permissible bus-devfn source addresses for DMA
>>> @@ -5873,8 +5874,14 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
>>>  * cannot be left as a userspace activity).  DMA aliases should therefore
>>>  * be configured via quirks, such as the PCI fixup header quirk.
>>>  */
>>> -void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
>>> +void pci_add_dma_alias(struct pci_dev *dev, u8 devfn_from, unsigned nr_devfns)
>>> {
>>> +	int devfn_to;
>>> +
>>> +	if (nr_devfns > U8_MAX+1)
>>> +		nr_devfns = U8_MAX+1;
>>
>> Why +1? That doesn't seem right to me….
> 
> U8_MAX is the max number U8 can represent(255) but is one less than the number 
> of values it can represent(256). devfns can be 0.0 to 1f.7 inclusive(I think) 
> so the number of possible devfns is 256. Thinking about it, maybe the 
> zalloc should be U8_MAX+1 too?
> 
> I might be wrong though, what do you reckon?

Right, yes, but I actually think the original code is wrong. It's only
allocating a bitmap that holds 255 values and you're trying to insert
256 ones into that bitmap. It's probably ok, because there's no way to
allocate an odd sized bitmap, but it's probably worth fixing for clarity.

It also looks wrong in pci_for_each_dma_alias() as well, so I'd probably
fix both those up in a separate prep-patch.

Logan
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2019-11-29 17:27 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-24 12:52 [PATCH] Ensure pci transactions coming from PLX NTB are handled when IOMMU is turned on James Sewart via iommu
2019-11-05 12:17 ` James Sewart via iommu
2019-11-20 17:48   ` Dmitry Safonov
2019-11-20 19:30     ` Logan Gunthorpe
2019-11-20 19:49       ` Bjorn Helgaas
2019-11-20 19:32     ` Bjorn Helgaas
2019-11-26 17:03       ` [PATCH v2] PCI: Add DMA alias quirk for PLX PEX NTB James Sewart via iommu
2019-11-26 17:06         ` Logan Gunthorpe
2019-11-26 17:36           ` [PATCH v3 1/2] PCI: Add helper pci_add_dma_alias_range James Sewart via iommu
2019-11-26 17:37             ` [PATCH v3 2/2] PCI: Add DMA alias quirk for PLX PEX NTB James Sewart via iommu
2019-11-26 17:38         ` [PATCH v2] " Christoph Hellwig
2019-11-27 13:27           ` [PATCH v3 1/2] PCI: Add parameter nr_devfns to pci_add_dma_alias James Sewart via iommu
2019-11-27 13:28             ` [PATCH v3 2/2] PCI: Add DMA alias quirk for PLX PEX NTB James Sewart via iommu
2019-11-27 17:38             ` [PATCH v3 1/2] PCI: Add parameter nr_devfns to pci_add_dma_alias Logan Gunthorpe
2019-11-29 12:49               ` [PATCH v4 " James Sewart via iommu
2019-11-29 12:49                 ` [PATCH v4 2/2] PCI: Add DMA alias quirk for PLX PEX NTB James Sewart via iommu
2019-11-29 16:50                 ` [PATCH v4 1/2] PCI: Add parameter nr_devfns to pci_add_dma_alias Logan Gunthorpe
2019-11-29 17:19                   ` James Sewart via iommu
2019-11-29 17:26                     ` Logan Gunthorpe [this message]
2019-11-29 17:56                       ` [PATCH v5 1/3] PCI: Fix off by one in dma_alias_mask allocation size James Sewart via iommu
2019-11-29 17:56                         ` [PATCH v5 2/3] PCI: Add parameter nr_devfns to pci_add_dma_alias James Sewart via iommu
2019-11-29 17:57                           ` [PATCH v5 3/3] PCI: Add DMA alias quirk for PLX PEX NTB James Sewart via iommu
2019-12-02 17:03                           ` [PATCH v5 2/3] PCI: Add parameter nr_devfns to pci_add_dma_alias Christoph Hellwig
2019-11-29 17:58                         ` [PATCH v5 1/3] PCI: Fix off by one in dma_alias_mask allocation size Logan Gunthorpe
2019-12-02 17:03                         ` Christoph Hellwig

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=d811576e-0f89-2303-a554-2701af5c5647@deltatee.com \
    --to=logang@deltatee.com \
    --cc=0x7f454c46@gmail.com \
    --cc=alex.williamson@redhat.com \
    --cc=dima@arista.com \
    --cc=helgaas@kernel.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jamessewart@arista.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).