Date: Tue, 24 Apr 2007 17:29:28 -0400 From: Kris Kennaway <kris@obsecurity.org> To: John Baldwin <jhb@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/amd64/amd64 vm_machdep.c src/sys/i386/i386 vm_machdep.c Message-ID: <20070424212927.GA39974@xor.obsecurity.org> In-Reply-To: <200704241721.46689.jhb@freebsd.org> References: <200704242117.l3OLHjRn017578@repoman.freebsd.org> <200704241721.46689.jhb@freebsd.org>
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On Tue, Apr 24, 2007 at 05:21:46PM -0400, John Baldwin wrote: > On Tuesday 24 April 2007 05:17:45 pm John Baldwin wrote: > > jhb 2007-04-24 21:17:45 UTC > > > > FreeBSD src repository > > > > Modified files: > > sys/amd64/amd64 vm_machdep.c > > sys/i386/i386 vm_machdep.c > > Log: > > Fix the triple fault used as a last resort during a reboot to actually > > fault. The previous method zero'd out the page tables, invalidated the > > TLB, and then entered a spin loop. The idea was that the instruction > after > > the TLB invalidate would result in a page fault and the page fault and > > subsequent double fault wouldn't be able to determine the physical page > > for their fault handlers' first instruction. This stopped working when > > PGE (PG_G PTE/PDE bit) support was added as a TLB invalidate via %cr3 > > reload doesn't clear TLB entries with PG_G set. Thus, the CPU was still > > able to map the virtual address for the spin loop and happily performed > > its infinite loop. > > > > The triple fault now uses a much more deterministic sledge-hammer approach > > to generate a triple fault. First, the IDT descriptor is set to point to > > an empty IDT, so any interrupts (including a double fault) will instantly > > fault. Second, we trigger a int 3 breakpoint to force an interrupt and > > kick off a triple fault. > > > > MFC after: 3 days > > This and the other changes to support more methods for kicking off a reset > might fix problems people have with machines not rebooting but just hanging. > IIRC, there was a problem on some Dell 1950s that wouldn't reboot properly, > so they might be a good candidate for this. I ran into this at work on a > machine that didn't have a functional keyboard controller, so it didn't > reboot when the keyboard reset failed, but just hung. Some of my newer machines sometimes fail to reboot without power cycling, so I'll keep an eye out. Krishome | help
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