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Message-ID: <51C22A6B.3090009@zytor.com> Date: Wed, 19 Jun 2013 15:02:19 -0700 From: "H. Peter Anvin" <hpa@...or.com> To: Borislav Petkov <bp@...en8.de> CC: Dave Jones <davej@...hat.com>, Linux Kernel <linux-kernel@...r.kernel.org>, x86@...nel.org Subject: Re: [x86] only print out DR registers if they are not power-on defaults. On 06/19/2013 02:52 PM, Borislav Petkov wrote: > On Wed, Jun 19, 2013 at 02:42:49PM -0700, H. Peter Anvin wrote: >> There is serious confusion with regards to DR6 about the bits which >> are *fixed* (forced to 1) and the ones which are *reserved* (should >> always have a fixed value.) >> >> There are some bits in DR6 which are used by hardware probes. > > Haha, I knew it! HW guys don't care about the architectural documents. > > Maybe DR6 should probably be dropped altogether from the check before > exiting __show_regs early? > Uhm... I think you're missing the point of architectural documents. The architectural documents describe the contract between hardware and software. It doesn't mean that hardware can't go beyond it... it is in fact the norm. The architectural documentation states what software may rely on and within what bounds it can assume safe behavior to be compatible both now and with any future extensions. -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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