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 9D754C433EF for ; Mon, 11 Apr 2022 09:37:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233491AbiDKJjl (ORCPT ); Mon, 11 Apr 2022 05:39:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37588 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344552AbiDKJjW (ORCPT ); Mon, 11 Apr 2022 05:39:22 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3BA634090F; Mon, 11 Apr 2022 02:37:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1649669824; x=1681205824; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=j7yxrIW5JHTanE/rqGKH77B25ab5eWBeaxexb2VIdDk=; b=RpLbOXieJnlXFBKLCHkIGiU0K/MXMW/cB6tUYLDF4zquBKyMAEHUO7rU TU+5TVJoNaZdAFucFU4VVrndcxzPXMJ4zzKb98QFYIjvYKHt/dTQqJPjY oZdXtJVa6OOrvRaFBSQdhr0yzNWyaqFbzeEqMZ5PY4uYb5TQI2+fy6RHe eqow5XXErVT1/SLQV89ZwJWtSp1qG/KoPSf5FomqG/4qP5FalvwIBCTr5 pGyxG4vlCSfmdhGcIHSYmKNyzXmeZZXnYND7BrrKEysKDaOKfG9W7Y9Gf T18K3nMNfydpqWWCqsLbKbwsZeHBL1ikWrv93dYJFJyzmbhhLTfd0QgoO g==; X-IronPort-AV: E=McAfee;i="6400,9594,10313"; a="260923505" X-IronPort-AV: E=Sophos;i="5.90,251,1643702400"; d="scan'208";a="260923505" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2022 02:37:04 -0700 X-IronPort-AV: E=Sophos;i="5.90,251,1643702400"; d="scan'208";a="572050545" Received: from arthur-vostro-3668.sh.intel.com ([10.239.13.120]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2022 02:36:57 -0700 From: Zeng Guang To: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, Dave Hansen , Tony Luck , Kan Liang , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Kim Phillips , Jarkko Sakkinen , Jethro Beekman , Kai Huang Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Robert Hu , Gao Chao , Zeng Guang , Maxim Levitsky Subject: [PATCH v8 6/9] KVM: x86: lapic: don't allow to change APIC ID unconditionally Date: Mon, 11 Apr 2022 17:04:44 +0800 Message-Id: <20220411090447.5928-7-guang.zeng@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220411090447.5928-1-guang.zeng@intel.com> References: <20220411090447.5928-1-guang.zeng@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Maxim Levitsky No normal guest has any reason to change physical APIC IDs, and allowing this introduces bugs into APIC acceleration code. And Intel recent hardware just ignores writes to APIC_ID in xAPIC mode. More background can be found at: https://lore.kernel.org/lkml/Yfw5ddGNOnDqxMLs@google.com/ Looks there is no much value to support writable xAPIC ID in guest except supporting some old and crazy use cases which probably would fail on real hardware. So, make xAPIC ID read-only for KVM guests. Signed-off-by: Maxim Levitsky Signed-off-by: Zeng Guang --- arch/x86/kvm/lapic.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 137c3a2f5180..62d5ce4dc0c5 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2047,10 +2047,17 @@ static int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val) switch (reg) { case APIC_ID: /* Local APIC ID */ - if (!apic_x2apic_mode(apic)) - kvm_apic_set_xapic_id(apic, val >> 24); - else + if (apic_x2apic_mode(apic)) { ret = 1; + break; + } + /* Don't allow changing APIC ID to avoid unexpected issues */ + if ((val >> 24) != apic->vcpu->vcpu_id) { + kvm_vm_bugged(apic->vcpu->kvm); + break; + } + + kvm_apic_set_xapic_id(apic, val >> 24); break; case APIC_TASKPRI: @@ -2635,11 +2642,15 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu) static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s, bool set) { - if (apic_x2apic_mode(vcpu->arch.apic)) { - u32 *id = (u32 *)(s->regs + APIC_ID); - u32 *ldr = (u32 *)(s->regs + APIC_LDR); - u64 icr; + u32 *id = (u32 *)(s->regs + APIC_ID); + u32 *ldr = (u32 *)(s->regs + APIC_LDR); + u64 icr; + if (!apic_x2apic_mode(vcpu->arch.apic)) { + /* Don't allow changing APIC ID to avoid unexpected issues */ + if ((*id >> 24) != vcpu->vcpu_id) + return -EINVAL; + } else { if (vcpu->kvm->arch.x2apic_format) { if (*id != vcpu->vcpu_id) return -EINVAL; -- 2.27.0