From nobody Tue Apr 7 06:48:13 2026 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 6527AECAAA1 for ; Tue, 30 Aug 2022 23:17:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230508AbiH3XRt (ORCPT ); Tue, 30 Aug 2022 19:17:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231742AbiH3XRM (ORCPT ); Tue, 30 Aug 2022 19:17:12 -0400 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3047D9F1BE for ; Tue, 30 Aug 2022 16:16:25 -0700 (PDT) Received: by mail-pl1-x649.google.com with SMTP id l16-20020a170902f69000b00175138bcd25so2334385plg.2 for ; Tue, 30 Aug 2022 16:16:25 -0700 (PDT) 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; bh=tQH5mj5DXx8pDOg5+wg55pqynAIGnsFRb1EgCvXniyg=; b=pTQWse+nJwxm+r4pe+tWC4i8rGRAYXwYceIjdjBLn6lmePyYYyXsYxZF/mj7LFUfKy qgF08o0eK0D4v6CFJtSEHQYwlJAopF1ycK2haq12XM3oEtZU55/whez15jVRdCJEJEpW 70jZhhj2bUiUua9tPcnEIYrTYKVuI1+3AVpaJOr9d1Rb0KpekVFtqlVXsdKSS6/RcorK lXayw/8slmB185RAixROfy70CxHsiMs8p6yM3g4HR1Id2+T+WYk++nimIE5fLYPGdEN+ 3/Aec/wbh4mjGwPIuRfICITCznuXvhyZQUG0ZeFrnHek8PlidnAjVCBDE3R2yFNyyXuL BbCw== 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; bh=tQH5mj5DXx8pDOg5+wg55pqynAIGnsFRb1EgCvXniyg=; b=zIjUGtVkHTdGMw8nhTyagmFfs8VZFW8OTzUURMtzbxB/PAEPACRKYnbLgazbxzrdIu FB5qRsu8oKWFMWrsBMiLXafARl5NPFEdGDPFqMKfMWKsN+G3LDjAG1bWos7aF4TM3Zfm +NhLV8Coiwt9RC4yA/CS0/SKJdo0uLQ4mTXaoF1mhDIqzqeggA+E4OEh7WDxiMV+bdJP mf65OHpmgVeUkUD4cI5d7vfDK5mE716MY9Ht7uBxgIxKPgxG09bL/QeGVvV6PtiDIjC/ gj9ieXovnqugF++L0n96dqu0gNLBEKpG1/UhGo37rjjht1KmyZ+HqUsbtP2leT1y4Pp4 RyMA== X-Gm-Message-State: ACgBeo25fLu3KUdo0xS1QkunHxUna7kBFylXaCpLvk2udp0JCEIoLSpL wleYKa4aSbwxtGD4pzpbZzLOZlOtwSE= X-Google-Smtp-Source: AA6agR5SmoOabESqzgeL3XbiGJ9fl5e/kwquZZibIowi2wwuplpE/2byG8fZNALDzoNTqoiF00GnDVhNngc= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:6b0c:b0:171:325a:364e with SMTP id o12-20020a1709026b0c00b00171325a364emr22929892plk.150.1661901384910; Tue, 30 Aug 2022 16:16:24 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 30 Aug 2022 23:15:52 +0000 In-Reply-To: <20220830231614.3580124-1-seanjc@google.com> Mime-Version: 1.0 References: <20220830231614.3580124-1-seanjc@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220830231614.3580124-6-seanjc@google.com> Subject: [PATCH v5 05/27] KVM: x86: Suppress code #DBs on Intel if MOV/POP SS blocking is active From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jim Mattson , Maxim Levitsky , Oliver Upton , Peter Shier Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Suppress code breakpoints if MOV/POP SS blocking is active and the guest CPU is Intel, i.e. if the guest thinks it's running on an Intel CPU. Intel CPUs inhibit code #DBs when MOV/POP SS blocking is active, whereas AMD (and its descendents) do not. Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7403221c868e..013580c355d7 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8542,6 +8542,23 @@ int kvm_skip_emulated_instruction(struct kvm_vcpu *v= cpu) } EXPORT_SYMBOL_GPL(kvm_skip_emulated_instruction); =20 +static bool kvm_is_code_breakpoint_inhibited(struct kvm_vcpu *vcpu) +{ + u32 shadow; + + if (kvm_get_rflags(vcpu) & X86_EFLAGS_RF) + return true; + + /* + * Intel CPUs inhibit code #DBs when MOV/POP SS blocking is active, + * but AMD CPUs do not. MOV/POP SS blocking is rare, check that first + * to avoid the relatively expensive CPUID lookup. + */ + shadow =3D static_call(kvm_x86_get_interrupt_shadow)(vcpu); + return (shadow & KVM_X86_SHADOW_INT_MOV_SS) && + guest_cpuid_is_intel(vcpu); +} + static bool kvm_vcpu_check_code_breakpoint(struct kvm_vcpu *vcpu, int emulation_type, int *r) { @@ -8584,7 +8601,7 @@ static bool kvm_vcpu_check_code_breakpoint(struct kvm= _vcpu *vcpu, } =20 if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK) && - !(kvm_get_rflags(vcpu) & X86_EFLAGS_RF)) { + !kvm_is_code_breakpoint_inhibited(vcpu)) { unsigned long eip =3D kvm_get_linear_rip(vcpu); u32 dr6 =3D kvm_vcpu_check_hw_bp(eip, 0, vcpu->arch.dr7, --=20 2.37.2.672.g94769d06f0-goog