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, warrier@linux.vnet.ibm.com,
alex.williamson@redhat.com, paulus@samba.org,
bhelgaas@google.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs
Date: Fri, 1 Jul 2016 13:27:17 +0800 [thread overview]
Message-ID: <21112bd7-d343-46b6-1df1-b20cc1c1b24e@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160701003959.GB15147@gwshan>
Hi Gavin,
On 2016/7/1 8:39, Gavin Shan 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().
Thanks,
Yongji
next prev parent reply other threads:[~2016-07-01 5:28 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 [this message]
2016-07-01 6:05 ` Gavin Shan
2016-07-01 6:40 ` Yongji Xie
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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