Date: Fri, 18 Jun 2021 20:03:59 -0700 From: Neel Chauhan <nc@FreeBSD.org> To: Neel Chauhan <nc@freebsd.org> Cc: Mark Johnston <markj@freebsd.org>, current@freebsd.org Subject: Re: Kernel/driver hacking: panic: Assertion vm_object_busied((m->object)) failed at /usr/src/sys/vm/vm_page.c:5455 Message-ID: <61de965123274866935935bded6c3d58@FreeBSD.org> In-Reply-To: <389e4560afdc211e9915746b11a0d0d0@FreeBSD.org> References: <e542a0c737f24d15df0fadd985e94938@neelc.org> <YMpnf3DcEw6A/rzD@nuc> <8bd27c2a72ebfa9299bca7d930297faf@FreeBSD.org> <YMymO0fYbsHoK05J@nuc> <389e4560afdc211e9915746b11a0d0d0@FreeBSD.org>
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On 2021-06-18 12:19, Neel Chauhan wrote: >> I'm not sure. I'll just note that the Linux code appears to be trying >> to map a set of pages belonging to a scatter-gather list. Taking the >> physical address of the first page and assuming that all subsequent >> pages are physically contiguous doesn't seem correct, but this is what >> is happening in that loop, since each iteration simply increments pa >> by >> PAGE_SIZE. Good news! While I don't have a fix, I have figured out what the issue is. Apparently, the vm_start values is for some reason coming as 0 when it is passed into vm_fault_cpu(). That's why it's giving these errors: of course the address at 0 is mapped, it is (probably) used by the kernel. I will look more into it tomorrow, but my brother has come over to Seattle from Connecticut so I may not be able to dedicate as much time as I would like to. -Neel (nc@)
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