From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755465AbdK2P0w (ORCPT ); Wed, 29 Nov 2017 10:26:52 -0500 Received: from merlin.infradead.org ([205.233.59.134]:44198 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751111AbdK2P0v (ORCPT ); Wed, 29 Nov 2017 10:26:51 -0500 Date: Wed, 29 Nov 2017 16:26:31 +0100 From: Peter Zijlstra To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, richard.fellner@student.tugraz.at, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, bp@alien8.de, x86@kernel.org Subject: Re: [PATCH] x86/mm/kaiser: Flush the correct ASID in __native_flush_tlb_single() Message-ID: <20171129152631.GQ3326@worktop> References: <20171128095531.F32E1BC7@viggo.jf.intel.com> <20171129143526.GP3326@worktop> <27729551-ecd6-e4e9-d214-4ab03d8008da@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <27729551-ecd6-e4e9-d214-4ab03d8008da@linux.intel.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 29, 2017 at 07:21:23AM -0800, Dave Hansen wrote: > Yes, that works. Also, as I think about it, INVLPG is a safer > (bug-resistant) instruction to use too. INVPCID _can_ get the current > (kernel) ASID wrong, as we saw. But INVLPG always uses the current one > and can't be wrong about flushing the *current* ASID. > > I think Andy measured it to be faster than INVPCID too. > > So, maybe we should just remove INVPCID's use entirely. With my patches the below invpcid_flush_one() is the only remaining user (not counting flush_tlb_global). I know Andy hates on INVPCID, but I could not convince myself that doing a full user invalidate makes sense for flush_tlb_single(), then again maybe it does, the patch is trivial after this. > > arch/x86/include/asm/tlbflush.h | 23 +++++++---------------- > > 1 file changed, 7 insertions(+), 16 deletions(-) > > > > diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h > > index 481d5094559e..9587722162ee 100644 > > --- a/arch/x86/include/asm/tlbflush.h > > +++ b/arch/x86/include/asm/tlbflush.h > > @@ -438,29 +438,20 @@ static inline void __native_flush_tlb_single(unsigned long addr) > > { > > u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid); > > > > + asm volatile("invlpg (%0)" ::"r" (addr) : "memory"); > > + > > + if (!kaiser_enabled) > > + return; > > + > > /* > > * Some platforms #GP if we call invpcid(type=1/2) before > > * CR4.PCIDE=1. Just call invpcid in the case we are called > > * early. > > */ > > + if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE)) > > flush_user_asid(loaded_mm_asid); > > + else > > invpcid_flush_one(user_asid(loaded_mm_asid), addr); > > }