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Message-ID: <480CD5FF.3050708@zytor.com> Date: Mon, 21 Apr 2008 13:59:27 -0400 From: "H. Peter Anvin" <hpa@...or.com> To: Mathieu Desnoyers <compudj@...stal.dyndns.org> CC: Pavel Machek <pavel@....cz>, mingo@...e.hu, akpm@...l.org, Jeremy Fitzhardinge <jeremy@...p.org>, Steven Rostedt <rostedt@...dmis.org>, "Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5) Mathieu Desnoyers wrote: > * H. Peter Anvin (hpa@...or.com) wrote: >> Pavel Machek wrote: >>>> There is also the page fault case. I think putting this test in >>>> ret_from_exception would be both safe (it is executed for any >>>> exception return) and fast (exceptions are rare). >>> Eh? I thought that page fault is one of the hottest paths in kernel >>> (along with syscall and packet receive/send)... >>> Pavel > > On x86_64, we can pinpoint only the page faults returning to the kernel, > which are rare and only caused by vmalloc accesses. Ideally we could do > the same on x86_32. > Pinpoint, how? Ultimately you need a runtime test, and you better be showing that people are going to die unless before you add a cycle to the page fault path. I'm only slightly exaggerating that. -hpa -- 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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