Date: Sun, 31 Mar 2019 06:25:48 -0700 From: Chuck Tuffli <chuck@tuffli.net> To: Fabian Freyer <fabian.freyer@physik.tu-berlin.de> Cc: freebsd-emulation@freebsd.org, FreeBSD Hackers <freebsd-hackers@freebsd.org>, freebsd-virtualization@freebsd.org Subject: Re: core dumps running in bhyve Message-ID: <CAM0tzX0BhVB6PAqM=u7Uu_ByBew8u8Z5zOU_LCb4BUWw3ET7iA@mail.gmail.com> In-Reply-To: <79b6eebd-2320-1888-1162-d3ca5492670c@physik.tu-berlin.de> References: <CAM0tzX1SzErUO1eXuhiX8Swc7zrwDQz30bO3HfPAbyF3OM5RUQ@mail.gmail.com> <79b6eebd-2320-1888-1162-d3ca5492670c@physik.tu-berlin.de>
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On Fri, Dec 28, 2018 at 3:53 AM Fabian Freyer <fabian.freyer@physik.tu-berlin.de> wrote: > > CCing freebsd-virtualization@, because they might know more about this. > > Am 25.12.2018 um 02:24 schrieb Chuck Tuffli: > > Using the latest bhyve, I'm seeing core dumps in the guest when running: > > nvmecontrol identify nvme0 > > against the emulated NVMe drive. The location of the core dump changes > > from run to run, but I suspect the root cause is a memory corruption > > caused by the transfer of the Identify data (4KB) back to the guest. > > This transfer of data is actually a memcpy to an address returned from > > vm_map_gpa() based on the physical address provided by the guest. > > > > Based on the signature of one of the core dumps, I modified > > nvmecontrol to always pass a 4KB aligned buffer to the driver instead > > of the (typically) unaligned address of the structure on the stack. > > With this change, nvmecontrol in the guest no longer core dumps. What > > I don't understand is why this changes the behavior. Do the addresses > > passed to vm_map_gpa() need to be page aligned? > > AFAIK vm_map_gpa maps a page, so yes, it needs to be 4k-aligned. > > > Or did moving the > > memory location from the stack to the heap merely mitigate what is > > corrupted? Thanks Fabian for the redirect to a better list. FWIW, the issue is with bhyve's NVMe emulation code and not anything to do with vm_map_gpa() per se. See https://reviews.freebsd.org/D19695 for those who are curious. --chuck
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