From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f71.google.com (mail-pl0-f71.google.com [209.85.160.71]) by kanga.kvack.org (Postfix) with ESMTP id 3465C6B0253 for ; Wed, 29 Nov 2017 06:48:31 -0500 (EST) Received: by mail-pl0-f71.google.com with SMTP id h1so1155204plh.23 for ; Wed, 29 Nov 2017 03:48:31 -0800 (PST) Received: from bombadil.infradead.org (bombadil.infradead.org. [65.50.211.133]) by mx.google.com with ESMTPS id q1si1173049plb.432.2017.11.29.03.48.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Nov 2017 03:48:30 -0800 (PST) Date: Wed, 29 Nov 2017 12:48:14 +0100 From: Peter Zijlstra Subject: Re: [PATCH 4/6] x86/mm/kaiser: Support PCID without INVPCID Message-ID: <20171129114814.rait2d6u4gso5qqd@hirez.programming.kicks-ass.net> References: <20171129103301.131535445@infradead.org> <20171129103512.819130098@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171129103512.819130098@infradead.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, Thomas Gleixner Cc: Dave Hansen , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Brian Gerst , Denys Vlasenko , "H. Peter Anvin" , Josh Poimboeuf , Linus Torvalds , Rik van Riel , daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, linux-mm@kvack.org, michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at, richard.fellner@student.tugraz.at, Andy Lutomirski On Wed, Nov 29, 2017 at 11:33:05AM +0100, Peter Zijlstra wrote: > XXX we could do a much larger ALTERNATIVE, there is no point in > testing the mask if we don't have PCID support. This. > @@ -220,7 +215,27 @@ For 32-bit we have the following convent > .macro SWITCH_TO_USER_CR3 scratch_reg:req > STATIC_JUMP_IF_FALSE .Lend_\@, kaiser_enabled_key, def=1 > mov %cr3, \scratch_reg > - ADJUST_USER_CR3 \scratch_reg > + > + /* > + * Test if the ASID needs a flush. > + */ > + push \scratch_reg /* preserve CR3 */ > + andq $(0x7FF), \scratch_reg /* mask ASID */ > + bt \scratch_reg, PER_CPU_VAR(user_asid_flush_mask) > + jnc .Lnoflush_\@ > + > + /* Flush needed, clear the bit */ > + btr \scratch_reg, PER_CPU_VAR(user_asid_flush_mask) > + pop \scratch_reg /* original CR3 */ > + jmp .Ldo_\@ > + > +.Lnoflush_\@: > + pop \scratch_reg /* original CR3 */ > + ALTERNATIVE "", "bts $63, \scratch_reg", X86_FEATURE_PCID > + > +.Ldo_\@: > + /* Flip the PGD and ASID to the user version */ > + orq $(KAISER_SWITCH_MASK), \scratch_reg > mov \scratch_reg, %cr3 > .Lend_\@: > .endm Something like so seems to actually compile and generate sensible code, not tested it though. --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -216,6 +216,8 @@ For 32-bit we have the following convent STATIC_JUMP_IF_FALSE .Lend_\@, kaiser_enabled_key, def=1 mov %cr3, \scratch_reg + ALTERNATIVE "jmp .Ldo_\@", "", X86_FEATURE_PCID + /* * Test if the ASID needs a flush. */ @@ -231,7 +233,7 @@ For 32-bit we have the following convent .Lnoflush_\@: pop \scratch_reg /* original CR3 */ - ALTERNATIVE "", "bts $63, \scratch_reg", X86_FEATURE_PCID + bts $63, \scratch_reg .Ldo_\@: /* Flip the PGD and ASID to the user version */ @@ -266,6 +268,8 @@ For 32-bit we have the following convent .macro RESTORE_CR3 scratch_reg:req save_reg:req STATIC_JUMP_IF_FALSE .Lend_\@, kaiser_enabled_key, def=1 + ALTERNATIVE "jmp .Ldo_\@", "", X86_FEATURE_PCID + /* ASID bit 11 is for user */ bt $11, \save_reg /* @@ -287,7 +291,7 @@ For 32-bit we have the following convent jmp .Ldo_\@ .Lnoflush_\@: - ALTERNATIVE "", "bts $63, \save_reg", X86_FEATURE_PCID + bts $63, \save_reg .Ldo_\@: /* -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org