Re: [PATCH v5] vfio: fix workaround of BAR mapping

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 30-Jul-18 9:51 AM, Burakov, Anatoly wrote:
> On 29-Jul-18 9:44 AM, Jerin Jacob wrote:
>> -----Original Message-----
>>> Date: Thu, 26 Jul 2018 11:35:43 +0200
>>> From: Thomas Monjalon <thomas@monjalon.net>
>>> To: Takeshi Yoshimura <t.yoshimura8869@gmail.com>
>>> Cc: dev@dpdk.org, Anatoly Burakov <anatoly.burakov@intel.com>
>>> Subject: Re: [dpdk-dev] [PATCH v5] vfio: fix workaround of BAR mapping
>>>
>>>
>>> 20/07/2018 10:13, Takeshi Yoshimura:
>>>> Currently, VFIO will try to map around MSI-X table in the BARs. When
>>>> MSI-X table (page-aligned) size is equal to (page-aligned) size of BAR,
>>>> VFIO will just skip the BAR.
>>>>
>>>> Recent kernel versions will allow VFIO to map the entire BAR containing
>>>> MSI-X tables (*), so instead of trying to map around the MSI-X vector
>>>> or skipping the BAR entirely if it's not possible, we can now try
>>>> mapping the entire BAR first. If mapping the entire BAR doesn't
>>>> succeed, fall back to the old behavior of mapping around MSI-X table or
>>>> skipping the BAR.
>>>>
>>>> (*): "vfio-pci: Allow mapping MSIX BAR",
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
>>>> commit/?id=a32295c612c57990d17fb0f41e7134394b2f35f6
>>>>
>>>> Fixes: 90a1633b2347 ("eal/linux: allow to map BARs with MSI-X tables")
>>>>
>>>> Signed-off-by: Takeshi Yoshimura <t.yoshimura8869@gmail.com>
>>>> Reviewed-by: Anatoly Burakov <anatoly.burakov@intel.com>
>>
>>
>> This change set breaks thunderx/octeontx platform with following 
>> error.(Tested with 4.9.0 kernel)
>>
>> EAL:   probe driver: 177d:a034 net_thunderx
>> EAL:   using IOMMU type 1 (Type 1)
>> EAL: pci_map_resource(): cannot mmap(44, 0xffff60200000, 0x200000, 
>> 0x40000000000): Invalid argument (0xffffffffffffffff)
>> EAL: PCI device 0001:01:00.2 on NUMA socket 0
>> EAL:   probe driver: 177d:a034 net_thunderx
>> EAL: pci_map_resource(): cannot mmap(47, 0xffff60600000, 0x200000, 
>> 0x40000000000): Invalid argument (0xffffffffffffffff)
>>
>> According Linux kernel change, user space application suppose to use 
>> VFIO_REGION_INFO_CAP_MSIX_MAPPABLE
>> capability to detect this feature to work < 4.15 kernel. Right? if so, 
>> Why we
>> are doing this retry based logic?
> 
> I don't think anything's broken there - just a gratuitous error message.
> 
> But yes, i seem to have missed the region info flag. It was my 
> suggestion to use the retry logic. I'll submit a patch fixing this.
> 

The patch to fix it involves way more work than i am comfortable with 
submitting to rc3, so i believe we should revert this patch and postpone 
the change to 18.11.


-- 
Thanks,
Anatoly