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 3CC1DC43334 for ; Fri, 22 Jul 2022 09:30:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235234AbiGVJaD (ORCPT ); Fri, 22 Jul 2022 05:30:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236146AbiGVJ26 (ORCPT ); Fri, 22 Jul 2022 05:28:58 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19E76CE515; Fri, 22 Jul 2022 02:18:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 72B32B827C5; Fri, 22 Jul 2022 09:18:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB6E0C341C6; Fri, 22 Jul 2022 09:18:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1658481485; bh=/9dcsr870ov51eEEK1dkzhiiBqllUNp5Vnz/i1/93Tw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=avy/PcbMw+zAnbKKrGVFtoGVvN/d5P1hxLgUY+WNw/GbPUcyRj6sC9N2OMcjfvH2q HTX8BbEPlDaBJl3WOpM5QLr5r5UCqtTMLarOhMNyO/xpl2RyKo5/cxAEPbwWFQDPVl pDFyTEhUQS7CP2dAmMrgKmsX4DWdMnZ68Re21ojY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Linus Torvalds , Paolo Bonzini Subject: [PATCH 5.15 84/89] KVM: emulate: do not adjust size of fastop and setcc subroutines Date: Fri, 22 Jul 2022 11:11:58 +0200 Message-Id: <20220722091138.039360409@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220722091133.320803732@linuxfoundation.org> References: <20220722091133.320803732@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo Bonzini commit 79629181607e801c0b41b8790ac4ee2eb5d7bc3e upstream. 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. Cc: stable@vger.kernel.org # 5.15.x: 84e7051c0bc1: x86/kvm: fix FASTOP_SIZE when return thunks are enabled Cc: stable@vger.kernel.org Suggested-by: Linus Torvalds Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/emulate.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -187,13 +187,6 @@ #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 : 56; u64 intercept : 8; @@ -307,9 +300,15 @@ static void invalidate_registers(struct * 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" \ @@ -441,9 +440,7 @@ static int fastop(struct x86_emulate_ctx * RET | JMP __x86_return_thunk [1,5 bytes; CONFIG_RETHUNK] * INT3 [1 byte; CONFIG_SLS] */ -#define SETCC_LENGTH (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" \