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Date: Sat, 05 Apr 2008 15:39:05 +0300 From: Avi Kivity <avi@...ranet.com> To: Pekka Enberg <penberg@...helsinki.fi> CC: Pekka Paalanen <pq@....fi>, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, Christoph Hellwig <hch@...radead.org>, Arjan van de Ven <arjan@...radead.org>, Pavel Roskin <proski@....org>, Steven Rostedt <rostedt@...dmis.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, vegard.nossum@...il.com Subject: Re: mmiotrace bug: recursive probe hit Pekka Enberg wrote: > On Sat, Apr 5, 2008 at 10:36 AM, Avi Kivity <avi@...ranet.com> wrote: > >> It should not be too difficult to modify x86_emulate.c to do everything >> through a function vector. However there is a simpler (for you) solution: >> run the driver-to-be-reverse-engineered in a kvm guest, and modify kvm >> userspace to log accesses to mmio regions. This requires the not-yet-merged >> pci passthrough support. You can reverse engineer Windows drivers with this >> as well. >> >> This won't work for kmemcheck smp though. >> > > For kmemcheck, I'd prefer the per-CPU page tables suggested by Ingo. > I'm having hard time understanding why that's a "ugly hack" compared > to using kvm for this... > It's not an ugly hack, but will be very very difficult. With mmu notifiers it's probably doable though: - the linux page tables are never loaded into cr3, but rather kept as a reference - page faults are by instantiating ptes into shadow page tables (which track the linux page tables) - mmu notifiers are used to drop shadow ptes when the linux ptes change -- Any sufficiently difficult bug is indistinguishable from a feature. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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