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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60F24CA9EAE for ; Tue, 29 Oct 2019 12:17:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25D0F20717 for ; Tue, 29 Oct 2019 12:17:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gCso8YSQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731485AbfJ2MRU (ORCPT ); Tue, 29 Oct 2019 08:17:20 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:26750 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727082AbfJ2MRU (ORCPT ); Tue, 29 Oct 2019 08:17:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572351439; 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: in-reply-to:in-reply-to:references:references; bh=c5TVCYf2MyQ5m7UVpCqBCLIUTH2CBfxMSLxMHSp3UXw=; b=gCso8YSQKB2mbv431nmp+frf4w9LlzMZOobkUSCWl3MDrh8dZ8jzJxlCx38AK+/WbY4K0I edSxoWzpf/Ej+aGgACN58tAQ116KAEnbpXiQ0oGIZvXtOB3H2ibQTFppiyOS/mOAKek5mm IAv7a/tgOu48TGpjonSmZeoABPGyF8I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-14-1I3Ni04hMhG__5_pXeNLHQ-1; Tue, 29 Oct 2019 08:17:15 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 29E9C107AD28; Tue, 29 Oct 2019 12:17:14 +0000 (UTC) Received: from [10.36.118.15] (unknown [10.36.118.15]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 728CC600C4; Tue, 29 Oct 2019 12:17:10 +0000 (UTC) Subject: Re: [PATCH 3/3] KVM: arm/arm64: vgic: Don't rely on the wrong pending table To: Zenghui Yu , maz@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com Cc: wanghaibin.wang@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20191029071919.177-1-yuzenghui@huawei.com> <20191029071919.177-4-yuzenghui@huawei.com> From: Auger Eric Message-ID: <5e4d1a2f-7107-efe3-9dde-626662e31ac5@redhat.com> Date: Tue, 29 Oct 2019 13:17:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20191029071919.177-4-yuzenghui@huawei.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: 1I3Ni04hMhG__5_pXeNLHQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Zenghui, Marc, On 10/29/19 8:19 AM, Zenghui Yu wrote: > It's possible that two LPIs locate in the same "byte_offset" but target > two different vcpus, where their pending status are indicated by two > different pending tables. In such a scenario, using last_byte_offset > optimization will lead KVM relying on the wrong pending table entry. > Let us use last_ptr instead, which can be treated as a byte index into > a pending table and also, can be vcpu specific. >=20 > Signed-off-by: Zenghui Yu > --- >=20 > If this patch has done the right thing, we can even add the: >=20 > Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_= TABLES") >=20 > But to be honest, I'm not clear about what has this patch actually fixed. > Pending tables should contain all zeros before we flush vgic_irq's pendin= g > status into guest's RAM (thinking that guest should never write anything > into it). So the pending table entry we've read from the guest memory > seems always be zero. And we will always do the right thing even if we > rely on the wrong pending table entry. >=20 > I think I must have some misunderstanding here... Please fix me. >=20 > virt/kvm/arm/vgic/vgic-v3.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) >=20 > diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c > index 5ef93e5041e1..7cd2e2f81513 100644 > --- a/virt/kvm/arm/vgic/vgic-v3.c > +++ b/virt/kvm/arm/vgic/vgic-v3.c > @@ -363,8 +363,8 @@ int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, = struct vgic_irq *irq) > int vgic_v3_save_pending_tables(struct kvm *kvm) > { > =09struct vgic_dist *dist =3D &kvm->arch.vgic; > -=09int last_byte_offset =3D -1; > =09struct vgic_irq *irq; > +=09gpa_t last_ptr =3D -1; > =09int ret; > =09u8 val; > =20 > @@ -384,11 +384,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm) > =09=09bit_nr =3D irq->intid % BITS_PER_BYTE; > =09=09ptr =3D pendbase + byte_offset; > =20 > -=09=09if (byte_offset !=3D last_byte_offset) { > +=09=09if (ptr !=3D last_ptr) { > =09=09=09ret =3D kvm_read_guest_lock(kvm, ptr, &val, 1); > =09=09=09if (ret) > =09=09=09=09return ret; > -=09=09=09last_byte_offset =3D byte_offset; > +=09=09=09last_ptr =3D ptr; > =09=09} > =20 > =09=09stored =3D val & (1U << bit_nr); >=20 Acked-by: Eric Auger Thanks for fixing this. Eric