Date: Sun, 20 Jun 2021 10:36:40 +0200 From: Hans Petter Selasky <hps@selasky.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: <6df7b46d-26ca-b897-66fd-b6a441475348@selasky.org> In-Reply-To: <ea775950a74b75134a9f0193ba39e8b6@FreeBSD.org> References: <e542a0c737f24d15df0fadd985e94938@neelc.org> <YMpnf3DcEw6A/rzD@nuc> <8bd27c2a72ebfa9299bca7d930297faf@FreeBSD.org> <YMymO0fYbsHoK05J@nuc> <389e4560afdc211e9915746b11a0d0d0@FreeBSD.org> <61de965123274866935935bded6c3d58@FreeBSD.org> <ea775950a74b75134a9f0193ba39e8b6@FreeBSD.org>
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On 6/20/21 7:32 AM, Neel Chauhan wrote: > On 2021-06-18 20:03, Neel Chauhan wrote: >> 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. > > An update: The vm_start 0 seems to be expected. I checked the values > with printf()s. > > I have posted this on Twitter, and am considering hiring a kernel > consultant to help if I am unable to do this on my own. > > So I am guessing this line (Line 231) is incorrect: > > pa = sg_dma_address(sgl); > > Source: > https://github.com/neelchauhan/drm-kmod/blob/d0eee96973ee0772e977b813678f92c5becf0507/drivers/gpu/drm/i915/intel_freebsd.c#L231 Hi Neel, sg_dma_address() is zero, because the memory hasn't been loaded. 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. Also, there is a superfluous "pa = " in the beginning of the function. --HPS
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