From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40E24C433EF for ; Fri, 15 Jul 2022 11:49:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234739AbiGOLtm (ORCPT ); Fri, 15 Jul 2022 07:49:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229475AbiGOLti (ORCPT ); Fri, 15 Jul 2022 07:49:38 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id DD4A5371AD for ; Fri, 15 Jul 2022 04:49:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657885777; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=ie8S/4kslSZgdmx6wrSNJRQWWqTbqopyobh+d0XIkq8=; b=LMB5TmBpk793gob/kfQTpstn4BGOJfSVXPWC7GL7gDbon9g7A4dxxv6tSj5B4V/Zorp9fU P3y7OVeZM30UdC9vKBaa6XNnUi2NmsEpcE6u89V70itJy9//xaJSd9ROHK7DYGSUrTngAw dZZNKpbw7da/Wbi9gWcybpBqNG54fRw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-644-seCiYla0MFacY20sMg_2JA-1; Fri, 15 Jul 2022 07:49:27 -0400 X-MC-Unique: seCiYla0MFacY20sMg_2JA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 67777801590; Fri, 15 Jul 2022 11:49:27 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 397E5140EBE3; Fri, 15 Jul 2022 11:49:27 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: x86@kernel.org, peterz@infradead.org, bp@suse.de, Linus Torvalds Subject: [PATCH] KVM: emulate: do not adjust size of fastop and setcc subroutines Date: Fri, 15 Jul 2022 07:49:27 -0400 Message-Id: <20220715114927.1460356-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Instead of doing complicated calculations to find the size of the subroutines (which are even more complicated because they need to be stringified into an asm statement), just hardcode to 16. It is less dense for a few combinations of IBT/SLS/retbleed, but it has the advantage of being really simple. Suggested-by: Linus Torvalds Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 0a15b0fec6d9..f8382abe22ff 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -189,13 +189,6 @@ #define X8(x...) X4(x), X4(x) #define X16(x...) X8(x), X8(x) -#define NR_FASTOP (ilog2(sizeof(ulong)) + 1) -#define RET_LENGTH (1 + (4 * IS_ENABLED(CONFIG_RETHUNK)) + \ - IS_ENABLED(CONFIG_SLS)) -#define FASTOP_LENGTH (ENDBR_INSN_SIZE + 7 + RET_LENGTH) -#define FASTOP_SIZE (8 << ((FASTOP_LENGTH > 8) & 1) << ((FASTOP_LENGTH > 16) & 1)) -static_assert(FASTOP_LENGTH <= FASTOP_SIZE); - struct opcode { u64 flags; u8 intercept; @@ -310,9 +303,15 @@ static void invalidate_registers(struct x86_emulate_ctxt *ctxt) * Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for * different operand sizes can be reached by calculation, rather than a jump * table (which would be bigger than the code). + * + * The 16 byte alignment, considering 5 bytes for the RET thunk, 3 for ENDBR + * and 1 for the straight line speculation INT3, leaves 7 bytes for the + * body of the function. Currently none is larger than 4. */ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop); +#define FASTOP_SIZE 16 + #define __FOP_FUNC(name) \ ".align " __stringify(FASTOP_SIZE) " \n\t" \ ".type " name ", @function \n\t" \ @@ -446,9 +445,7 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop); * RET | JMP __x86_return_thunk [1,5 bytes; CONFIG_RETHUNK] * INT3 [1 byte; CONFIG_SLS] */ -#define SETCC_LENGTH (ENDBR_INSN_SIZE + 3 + RET_LENGTH) -#define SETCC_ALIGN (4 << ((SETCC_LENGTH > 4) & 1) << ((SETCC_LENGTH > 8) & 1)) -static_assert(SETCC_LENGTH <= SETCC_ALIGN); +#define SETCC_ALIGN 16 #define FOP_SETCC(op) \ ".align " __stringify(SETCC_ALIGN) " \n\t" \ -- 2.31.1