From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas.monjalon@6wind.com>
Subject: Re: [bug] dpdk-vfio: Invalid region/index assumption
Date: Thu, 28 Jul 2016 08:54:42 +0200
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Cc: dev@dpdk.org, anatoly.burakov@intel.com
To: Alex Williamson <alex.williamson@redhat.com>
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Hi,

2016-07-27 16:14, Alex Williamson:
> I took a quick look at the dpdk vfio code and spotted an invalid
> assumption that should probably be corrected ASAP.

It can theoretically be a bug but the value may never change in the kernel,
right?
So when you say ASAP, I feel it can wait the next DPDK release
(we plan to release today).
Do you agree?

> That is:
> 
> lib/librte_eal/linuxapp/eal/eal_vfio.h:
> #define VFIO_GET_REGION_ADDR(x) ((uint64_t) x << 40ULL)
> #define VFIO_GET_REGION_IDX(x) (x >> 40)
> 
> Region offset to index is an implementation detail of the kernel, the
> vfio API defines that the offset of a given region (BAR) is found via
> the offset field of struct vfio_region_info returned via the
> VFIO_DEVICE_GET_REGION_INFO ioctl.  You're free to cache the offset
> into any sort of local variable you like, but the kernel may change the
> implementation of region index to offset at any point in time.  This is
> explicitly not part of the ABI.  Is there a place to file a bug, or is
> this sufficient?  Thanks,

Thanks for the report. This email is sufficient :)