Date: Mon, 4 Apr 2016 20:58:47 -0400 From: Ryan Stone <rysto32@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: FreeBSD Current <freebsd-current@freebsd.org>, Konstantin Belousov <kostikbel@gmail.com> Subject: Re: accessing a PCIe register from userspace through kmem or other ways ? Message-ID: <CAFMmRNzpOgBPsBezOyUZ_=qjCywfADx8MuJWdaWb_D%2B7UCmi7Q@mail.gmail.com> In-Reply-To: <9376230.YZMFsgSvTf@ralph.baldwin.cx> References: <CA%2BhQ2%2BiU4odjhaNicFA4QjvSZR2OZOOy%2BFu4LTqsibdoK4M8zg@mail.gmail.com> <CAFMmRNxJDuQoC-YuwbaWkj7MGVw9UgPEANOX6bN=i8%2Bp_9vm5w@mail.gmail.com> <20160401170458.GV1741@kib.kiev.ua> <9376230.YZMFsgSvTf@ralph.baldwin.cx>
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On Mon, Apr 4, 2016 at 6:45 PM, John Baldwin <jhb@freebsd.org> wrote: > I suspect Ryan might be referring to BARs outside of the DMAP which we > only populate to Maxmem IIRC. /dev/mem should work for those. > Unfortunately I no longer have access to the systems so I can't really confirm. I had a debug tool that attempted to read PCI device registers through /dev/mem, and on these systems (which were running a 8.2 derivative) the reads from /dev/mem failed with some kind of error. The one detail that I do remember is that the errors started happening after we enabled the use of 64-bit BARs in the BIOS and the addresses assigned to the BARs were quite large -- I believe well beyond the bounds of real memory.
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