Date: Wed, 17 Sep 2025 12:25:46 -0700 From: Chuck Tuffli <chuck@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-virtualization@freebsd.org, Mark Johnston <markj@freebsd.org> Subject: Re: Max BAR size for passthru? Message-ID: <CAKAYmMJc2VaxSEMPpoZD-rGdbOmjTXDA3gXDw2tj0%2BcT5Lpc1Q@mail.gmail.com> In-Reply-To: <83666dad-078b-4634-b66c-3153be957567@FreeBSD.org> References: <CAKAYmM%2BiMb%2B-CLWp05f-0sC2fmodPwOJWY4Xs6si8oXWaoN%2BdA@mail.gmail.com> <83666dad-078b-4634-b66c-3153be957567@FreeBSD.org>
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On Tue, Sep 16, 2025 at 4:12=E2=80=AFAM John Baldwin <jhb@freebsd.org> wrot= e: > > On 9/15/25 14:58, Chuck Tuffli wrote: > > I'm trying to get PCI passthru of an AMD GPU working, and am seeing > > what I think is a problem mapping the device's BAR into the guest. The > > host shows: ... > Hmmm, I think it would be useful if you could dump the effective memory > mappings for the guest PAs (the vm_map passed to vm_map_find) to see why > it is failing. Note that the request that is failing is for 2M, not > 256M, so I'm curious if the address is wrong somehow (why isn't it > 0x810000000?) Might be good to confirm which BAR it is trying to > allocate GPA space for. This was a good suggestion as it showed I was running into the guest seeing a "resizable BAR" and trying to resize them. The original host address to guest mapping was fine. Things went poorly after the guest tried to resize the bar. Thanks again for your help! --chuck
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