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Date:      Wed, 11 Jan 2017 18:48:10 -0800
From:      <soralx@cydem.org>
To:        <grehan@freebsd.org>
Cc:        <freebsd-virtualization@freebsd.org>
Subject:   Re: Issues with GTX960 on CentOS7 using bhyve PCI passthru (FreeBSD 11-RC2)
Message-ID:  <20170111184810.5e9fb07f@mscad14>
In-Reply-To: <93196ea2-5439-49ff-54fd-7b7273bdec85@freebsd.org>
References:  <20170110003332.7cf8ba15@mscad14> <0de7e0fe-5680-b1be-bd57-6bf446c2fd38@talk2dom.com> <0c927784-3e3f-7946-fba9-c25001f4156c@talk2dom.com> <20170110180117.7f246b5a@mscad14> <20170111014544.70670784@mscad14> <93196ea2-5439-49ff-54fd-7b7273bdec85@freebsd.org>

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> Hi,
> 
> >> The problem appears to be in the area of assigning memory-mapped
> >> I/O ranges by bhyve for the VGA card to a region outside of the
> >> CPU's addressable space; i.e., bhyve does not check CPUID's
> >> 0x80000008 AL value (0x27 for my CPU, which is 39 bits -- while
> >> bhyve assigns 0xd000000000 & above for the large Prefetch Memory
> >> chunks, which requires 40 address bits).  
> 
>   That's correct - it's a bug in bhyve.

Baking a proper fix will be more complicated by the fact that PCIe
cards themselves may have limitations. For example, most nVidia GPUs
have 40 bits DMA addressing capability, some 39, an a few (still
modern) ones -- just 37 [ref. nVidia "README" in the driver package].

>   PCI passthru doesn't allow the BAR values to be modified (this could 
> be changed, but it's a lot of work for little gain).

Removing another signature of detecting virtualization and increasing
compatibility would be negligible gain? Just asking...

> > But:
> >   # ./nvidia-smi
> >   No devices were found
> > dmesg:
> >   [  173.498953] NVRM: RmInitAdapter failed! (0x53:0x3:1856)
> >   [  173.499115] NVRM: rm_init_adapter failed for device bearing
> > minor number 0  
> 
>   Looks like you're getting close :)

Hmm, I'm not seeing myself getting much closer here. Do you know
something I don't? ;) I really hope bhyve developers can spare a
bit of time on getting GPU passthrough to work... I know nothing
about these things, and where I waste half a day messing around,
the problem could be fixed in half an hour by someone who knows.

> later,
> Peter.

-- 
[SorAlx]  ridin' VN2000 Classic LT



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