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Message-ID: <CAJvTdKnW8oxksSZRf8X19vDG3SwnkOfQC601Bcc5odJ9FFETzA@mail.gmail.com> Date: Mon, 3 Aug 2015 13:20:15 -0400 From: Len Brown <lenb@...nel.org> To: Pavel Machek <pavel@....cz> Cc: X86 ML <x86@...nel.org>, Linux PM list <linux-pm@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Len Brown <len.brown@...el.com> Subject: Re: [PATCH 1/1] x86: replace RDRAND forced-reseed with simple sanity check > If we trust built-in-self-test... > why do we need to do this at all? We > should check the return value at every call, anyway... Yes, we do trust built-in-self-test. Yes, we do check for errors on on every call, not just here in boot. The sanity check at boot from the kernel allows Linux to disable the feature, preventing user-space from thrashing trying to use it. There is also a line of reasoning that if the circuit is going to fail, chances are that it will fail immediately. I have no reason to believe that the circuit will fail in the field either at run-time or at boot-time. But that line of reasoning suggests that O(1 usec) to check at boot is a prudent investment -- it is certainly a better investment per time than may of the other things Linux does. thanks, Len Brown, Intel Open Source Technology Center -- 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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