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Date: Mon, 27 Apr 2015 11:47:30 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Borislav Petkov <bp@...en8.de> Cc: Andy Lutomirski <luto@...capital.net>, Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Denys Vlasenko <vda.linux@...glemail.com>, Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, Ingo Molnar <mingo@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, Oleg Nesterov <oleg@...hat.com>, Frederic Weisbecker <fweisbec@...il.com>, Alexei Starovoitov <ast@...mgrid.com>, Will Drewry <wad@...omium.org>, Kees Cook <keescook@...omium.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue On Mon, Apr 27, 2015 at 11:38 AM, Borislav Petkov <bp@...en8.de> wrote: > > So our current NOP-infrastructure does ASM_NOP_MAX NOPs of 8 bytes so > without more invasive changes, our longest NOPs are 8 byte long and then > we have to repeat. Btw (and I'm too lazy to check) do we take alignment into account? Because if you have to split, and use multiple nops, it is *probably* a good idea to try to avoid 16-byte boundaries, since that's can be the I$ fetch granularity from L1 (although I guess 32B is getting more common). So the exact split might depend on the alignment of the nop replacement.. > You can recognize the p6_nops being the same as in-the-manual-suggested > F16h ones. Can we perhaps get rid of the distinction entirely, and just use one set of 64-bit nops for both Intel/AMD? Linus -- 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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