[Bug 279830] Using AMD EPYC 9374F 32-Core Processor, PF driver gives error when loading for more than 62 VFs

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=279830

--- Comment #4 from vdubey@maxlinear.com ---
Also, I had further debugged this issue.

I had run 64 VFs on server with Intel CPUs (Intel 6342) which can successfully
load my PF driver. The log is as follows:

dre_drv0: DRE_drvIovInit: Called with num_vfs 64.
pcib7: allocated memory range (0xa3d00000-0xa40fffff) for rid 254 of dre_drv0
dre_drv0: Lazy allocation of 0x400000 bytes rid 0x254 type 3 at 0xa3d00000
pcib7: allocated memory range (0xa4100000-0xa41fffff) for rid 260 of dre_drv0
dre_drv0: Lazy allocation of 0x100000 bytes rid 0x260 type 3 at 0xa4100000
pcib7: attempting to grow memory window for (0-0xffffffff,0x2000000)
        front candidate range: 0xa1d00000-0xa3cfffff
        back candidate range: 0xa6280000-0xa827ffff
pcib7: grew memory window to 0xa1d00000-0xa62fffff
pcib7: allocated memory range (0xa1d00000-0xa3cfffff) for rid 264 of dre_drv0
dre_drv0: Lazy allocation of 0x2000000 bytes rid 0x264 type 3 at 0xa1d00000

In this case, as we can see that it was successfully able to "grew memory
window to 0xa1d00000-0xa62fffff". But in the case of AMD CPU, we are not able
to grow the memory space and get an error as seen in log below:

dre_drv0: DRE_drvIovInit: Called with num_vfs 64.
pcib15: allocated memory range (0xf9000000-0xf93fffff) for rid 254 of dre_drv0
dre_drv0: Lazy allocation of 0x400000 bytes rid 0x254 type 3 at 0xf9000000
pcib15: allocated memory range (0xf9400000-0xf94fffff) for rid 260 of dre_drv0
dre_drv0: Lazy allocation of 0x100000 bytes rid 0x260 type 3 at 0xf9400000
pcib15: attempting to grow memory window for (0-0xffffffff,0x2000000)
        front candidate range: 0xf7000000-0xf8ffffff
        back candidate range: 0xfb580000-0xfd57ffff
dre_drv0: 0x2000000 bytes of rid 0x264 res 3 failed (0, 0xffffffffffffffff).
dre_drv0: DRE_drvIovUnInit: Called.

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