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Message-ID: <AANLkTikCAbe5ATHjqgQDOFuCjcuG1=8e_5+ADaCQ3M6R@mail.gmail.com> Date: Fri, 11 Feb 2011 12:59:47 -0500 From: Brian Gerst <brgerst@...il.com> To: Jiri Olsa <jolsa@...hat.com> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, tglx@...utronix.de, mingo@...hat.com, x86@...nel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] x86_64: disable identity mappings statically On Fri, Feb 11, 2011 at 12:07 PM, Jiri Olsa <jolsa@...hat.com> wrote: > On Fri, Feb 11, 2011 at 08:46:41AM -0800, Eric W. Biederman wrote: >> Jiri Olsa <jolsa@...hat.com> writes: >> >> > hi, >> > >> > while browsing the page table setup code, I noticed the x86_64 head >> > code might not need the identity mappings at all. >> > It seems it's ok to switch it off completely from the begining, >> > unless I'm missing something. >> >> Have you tested it? > > yes, I booted it with no problem The only reason this doesn't crash is because the identity mappings provided by the boot code are marked as global, and therefore might not be flushed by simply loading cr3. The cpu can evict TLB entries at any time though, so it's a bad idea to run without the identity mappings even for the brief moment before jumping to the virtual address. -- Brian Gerst -- 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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