From: Yongji Xie <xyjxie@linux.vnet.ibm.com>
To: Gavin Shan <gwshan@linux.vnet.ibm.com>
Cc: nikunj@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com,
linux-doc@vger.kernel.org, aik@ozlabs.ru,
linux-pci@vger.kernel.org, corbet@lwn.net,
linux-kernel@vger.kernel.org, bhelgaas@google.com,
alex.williamson@redhat.com, paulus@samba.org,
warrier@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs
Date: Fri, 1 Jul 2016 14:40:16 +0800 [thread overview]
Message-ID: <ad90a18f-fcf3-b07d-f887-8daa6a313c77@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160701060519.GA8863@gwshan>
Hi Gavin,
On 2016/7/1 14:05, Gavin Shan wrote:
> On Fri, Jul 01, 2016 at 01:27:17PM +0800, Yongji Xie wrote:
>>> On Thu, Jun 30, 2016 at 06:53:08PM +0800, Yongji Xie wrote:
>>>> VF BARs are read-only zeroes according to SRIOV spec,
>>>> the normal way(writing BARs) of allocating resources wouldn't
>>>> be applied to VFs. The VFs' resources would be allocated
>>>> when we enable SR-IOV capability. So we should not try to
>>>> reassign alignment after we enable VFs. It's meaningless
>>>> and will release the allocated resources which leads to a bug.
>>>>
>>>> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
>>>> ---
>>>> drivers/pci/pci.c | 4 ++++
>>>> 1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>>>> index be8f72c..6ae02de 100644
>>>> --- a/drivers/pci/pci.c
>>>> +++ b/drivers/pci/pci.c
>>>> @@ -4822,6 +4822,10 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
>>>> resource_size_t align, size;
>>>> u16 command;
>>>>
>>>> + /* We should never try to reassign VF's alignment */
>>>> + if (dev->is_virtfn)
>>>> + return;
>>>> +
>>> Yongji, I think it's correct to ignore VF's BARs. Another concern is:
>>> it's safe to apply alignment to PF's IOV BARs? Lets have an extreme
>>> example here: one PF has 16 VFs; each VF has only one 1KB. It means
>>> the only PF IOV BAR is 16KB. I don't see how it works after expanding
>>> it to 64KB which is the page size. It might be not a problem on PowerNV
>>> platform, but potentially a issue on x86?
>> Seems like the alignment would not be applied to IOV BARs because
>> pci_reassigndev_resource_alignment() will be called before
>> sriov_init().
>>
> Correct, thanks for the claim. I guess the alignment applied to PF IOV
> BARs should be ignored as well? Anyway, the IOV BARs are retireved from
> SRIOV capability. It deserves a comment if you plan to take the change.
> Actually, the comment here (for ignoring alignment to VF BARs) can be
> improved a bit as well, it'd better why the alignment cannot be applied.
>
Do you mean we should ignore PF IOV BARs like this:
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4833,7 +4833,7 @@ void pci_reassigndev_resource_alignment(struct
pci_dev *dev)
command &= ~PCI_COMMAND_MEMORY;
pci_write_config_word(dev, PCI_COMMAND, command);
- for (i = 0; i < PCI_BRIDGE_RESOURCES; i++) {
+ for (i = 0; i <= PCI_ROM_RESOURCE; i++) {
r = &dev->resource[i];
if (!(r->flags & IORESOURCE_MEM))
continue;
Thanks,
Yongji
next prev parent reply other threads:[~2016-07-01 6:41 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-30 10:53 [PATCH v3 0/7] PCI: Add support for enforcing all MMIO BARs not to share PAGE_SIZE Yongji Xie
2016-06-30 10:53 ` [PATCH v3 1/7] PCI: Ignore enforced alignment when kernel uses existing firmware setup Yongji Xie
2016-07-01 0:28 ` Gavin Shan
2016-07-01 4:49 ` Yongji Xie
2016-06-30 10:53 ` [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs Yongji Xie
2016-07-01 0:39 ` Gavin Shan
2016-07-01 5:27 ` Yongji Xie
2016-07-01 6:05 ` Gavin Shan
2016-07-01 6:40 ` Yongji Xie [this message]
2016-07-02 0:31 ` Gavin Shan
2016-06-30 10:53 ` [PATCH v3 3/7] PCI: Do not disable memory decoding in pci_reassigndev_resource_alignment() Yongji Xie
2016-07-01 0:50 ` Gavin Shan
2016-07-01 6:35 ` Yongji Xie
2016-06-30 10:53 ` [PATCH v3 4/7] PCI: Add a new option for resource_alignment to reassign alignment Yongji Xie
2016-07-01 2:25 ` Gavin Shan
2016-07-01 6:53 ` Yongji Xie
2016-06-30 10:53 ` [PATCH v3 5/7] PCI: Do not use IORESOURCE_STARTALIGN to identify bridge resources Yongji Xie
2016-07-01 2:34 ` Gavin Shan
2016-07-01 7:04 ` Yongji Xie
2016-07-02 0:37 ` Gavin Shan
2016-06-30 10:53 ` [PATCH v3 6/7] PCI: Add support for enforcing all MMIO BARs to be page aligned Yongji Xie
2016-06-30 10:53 ` [PATCH v3 7/7] PCI: Add a macro to set default alignment for all PCI devices Yongji Xie
2016-07-12 5:09 ` [PATCH v3 0/7] PCI: Add support for enforcing all MMIO BARs not to share PAGE_SIZE Yongji Xie
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