Date: Sun, 20 Jun 2021 21:32:37 -0700 From: Neel Chauhan <nc@FreeBSD.org> To: Hans Petter Selasky <hps@selasky.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: <18a370deb9efbbb8d20a5eb3f00daf6d@FreeBSD.org> In-Reply-To: <6df7b46d-26ca-b897-66fd-b6a441475348@selasky.org> References: <e542a0c737f24d15df0fadd985e94938@neelc.org> <YMpnf3DcEw6A/rzD@nuc> <8bd27c2a72ebfa9299bca7d930297faf@FreeBSD.org> <YMymO0fYbsHoK05J@nuc> <389e4560afdc211e9915746b11a0d0d0@FreeBSD.org> <61de965123274866935935bded6c3d58@FreeBSD.org> <ea775950a74b75134a9f0193ba39e8b6@FreeBSD.org> <6df7b46d-26ca-b897-66fd-b6a441475348@selasky.org>
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Hi Hans, Sorry if I have to bother you again. On 2021-06-20 01:36, Hans Petter Selasky wrote: > sg_dma_address() is zero, because the memory hasn't been loaded. Makes sense! > You need to handle two cases there: > > When r->iobase is -1 and when it is not. > > I suspect you should add r->iobase to the sg_dma_address() only and > only when it is non -1. I have addressed it in my code. Hans, while your approach is correct (that's also done in Linux), for some reason it still crashes on vm_page_insert(). I must be doing "pa = " wrong. Stacktrace: https://misc.neelc.org/drm-kmod/stacktrace2.txt I have a separate function for getting the physical address: https://github.com/neelchauhan/drm-kmod/blob/5.7-wip/drivers/gpu/drm/i915/intel_freebsd.c#L219 This crash happens when "iobase == -1", so we execute Lines 228-231: - } else { struct sgt_iter sgt = __sgt_iter(sgl, 0); pa = (sgt.pfn + (sgt.curr >> PAGE_SHIFT)) << PAGE_SHIFT; } sgt.curr is zero, since (I believe) it's the first iteration. I have copied the Linux approach and ported what I felt was necessary, I am worried I am doing this wrong. > Also, there is a superfluous "pa = " in the beginning of the function. (Hopefully) I have cleaned it up. > --HPS -Neel (nc@)
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