From nobody Fri Sep 19 02:18:44 2025 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 363EEC4321E for ; Wed, 30 Nov 2022 23:37:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230043AbiK3XhH (ORCPT ); Wed, 30 Nov 2022 18:37:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55064 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229668AbiK3Xg5 (ORCPT ); Wed, 30 Nov 2022 18:36:57 -0500 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90E571128 for ; Wed, 30 Nov 2022 15:36:56 -0800 (PST) Received: by mail-pf1-x449.google.com with SMTP id 145-20020a621497000000b00574fab7294dso227737pfu.13 for ; Wed, 30 Nov 2022 15:36:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=KY6cgH0FoQgBjJK6cWHlNWc/cuNwA3rTkcmq/FIE/W0=; b=O5Kmt+7v3RpSCb0+VWEK9EqPSVW4nD/fCUmVYybP1v3f7uc0CVBZQJ6Mp82SSuZjF7 zmqc3E+bxzy+4Uq3+UDL+eohoq6ah6TrTNoVMvZHg4n+blU3QqemmrwiIawxne5qaD2T UConf3WriIgOVVFc0wl6okzHI4t82xGt4irFaBr3xR+F+tKQt3rl2uMUicSZ4RLGB9mZ L4lQxltIQF790VaPnhEgv3TVdq11vbEFZWepOygqrqfyQCJT5q3mxBQgc0290BBpcxCj r6Ta1DMsMNlerxvpH+yMMUmLS6f5AjQRavMBZ2mZ/a/ok3WETdkul8QghZxRpHT3AW/f vCcg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=KY6cgH0FoQgBjJK6cWHlNWc/cuNwA3rTkcmq/FIE/W0=; b=kJpX0xRPYYtITTix7Ybn79Zji4JU7QkVIEmQXhWUb739+X0QFIHJFiOQaHF4BQneRW 8uDV0Dxv4eg5oF51n2JBISyyMYYSgk5YqYD9XyRiEoYzMrxkmxn6q2mLiMW7mqRx+K+D mxy2DsbZMLzB5L9rNmqjpr26ShWvMG/ocFBET3WKaYGvFG5O8o+x2SujnuE/GjFm25a1 7KUgyE9FVOZptQ56RWj/R3GbtgFRETHmBQ2fTmtb1aOXLlc9vOX5Wz6FWfxPuixMKumb 9PuNWzoPONl1Mv3sfc8psahckh3f/evLnLvA8dC0kXuarxFa8SxxlgZgval0Y/qHa8Sb SlaQ== X-Gm-Message-State: ANoB5pnfTIVD2OF5jQEYy6YrTKJawWRNqiREYkrg/UU5aSFVB8IWWGya zWyBiAYpXALSbXD5GNunnaW1lcvmJto= X-Google-Smtp-Source: AA0mqf4eLRzKyfTQoTVAS0rlYdPo2PtSyno6QQQW3xQ9gUaSf2mV1RYEc8CRKCvPiAwwGbpbgWj5zcIKORc= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:903:1206:b0:186:a2ef:7a74 with SMTP id l6-20020a170903120600b00186a2ef7a74mr48409099plh.148.1669851416008; Wed, 30 Nov 2022 15:36:56 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 30 Nov 2022 23:36:48 +0000 In-Reply-To: <20221130233650.1404148-1-seanjc@google.com> Mime-Version: 1.0 References: <20221130233650.1404148-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog Message-ID: <20221130233650.1404148-3-seanjc@google.com> Subject: [PATCH v4 2/4] x86/virt: Force GIF=1 prior to disabling SVM (for reboot flows) From: Sean Christopherson To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Guilherme G . Piccoli" , Vitaly Kuznetsov , Paolo Bonzini , Sean Christopherson , Andrew Cooper , Tom Lendacky , stable@vger.kernel Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Set GIF=3D1 prior to disabling SVM to ensure that INIT is recognized if the kernel is disabling SVM in an emergency, e.g. if the kernel is about to jump into a crash kernel or may reboot without doing a full CPU RESET. If GIF is left cleared, the new kernel (or firmware) will be unabled to awaken APs. Eat faults on STGI (due to EFER.SVME=3D0) as it's possible that SVM could be disabled via NMI shootdown between reading EFER.SVME and executing STGI. Link: https://lore.kernel.org/all/cbcb6f35-e5d7-c1c9-4db9-fe5cc4de579a@amd.= com Cc: stable@vger.kernel.org Cc: Andrew Cooper Cc: Tom Lendacky Signed-off-by: Sean Christopherson --- arch/x86/include/asm/virtext.h | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h index 8757078d4442..0acb14806a74 100644 --- a/arch/x86/include/asm/virtext.h +++ b/arch/x86/include/asm/virtext.h @@ -126,7 +126,18 @@ static inline void cpu_svm_disable(void) =20 wrmsrl(MSR_VM_HSAVE_PA, 0); rdmsrl(MSR_EFER, efer); - wrmsrl(MSR_EFER, efer & ~EFER_SVME); + if (efer & EFER_SVME) { + /* + * Force GIF=3D1 prior to disabling SVM, e.g. to ensure INIT and + * NMI aren't blocked. Eat faults on STGI, as it #UDs if SVM + * isn't enabled and SVM can be disabled by an NMI callback. + */ + asm_volatile_goto("1: stgi\n\t" + _ASM_EXTABLE(1b, %l[fault]) + ::: "memory" : fault); +fault: + wrmsrl(MSR_EFER, efer & ~EFER_SVME); + } } =20 /** Makes sure SVM is disabled, if it is supported on the CPU --=20 2.38.1.584.g0f3c55d4c2-goog