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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 956A0CA9EAE for ; Tue, 29 Oct 2019 09:23:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6874120717 for ; Tue, 29 Oct 2019 09:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572341025; bh=/+vM46VmWpHXCwADQhd5+y+nI9Pi8Pytiog6MrqVFXE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=0UzFfq7EowEdDvpcf80u0wdgNgQdz9pDkkiP5Z8VRAjpQDXD2fhwGUZO7YfWgWE9W 2oqhhLDUuJ4KQfWv94QomszzpgGuoPUvJrYq73hU77bdfpj1K24ZIIuSVN7okJtO+s 2j1rsZcvDhUdO11CONC183GldPXJ+crnV7I38WnE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732582AbfJ2JXo (ORCPT ); Tue, 29 Oct 2019 05:23:44 -0400 Received: from inca-roads.misterjones.org ([213.251.177.50]:50926 "EHLO inca-roads.misterjones.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729316AbfJ2JXo (ORCPT ); Tue, 29 Oct 2019 05:23:44 -0400 Received: from [91.217.168.176] (helo=big-swifty.misterjones.org) by cheepnis.misterjones.org with esmtpsa (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.80) (envelope-from ) id 1iPNj0-0005iM-ET; Tue, 29 Oct 2019 10:23:38 +0100 Date: Tue, 29 Oct 2019 09:23:37 +0000 Message-ID: <86mudjykfa.wl-maz@kernel.org> From: Marc Zyngier To: Zenghui Yu Cc: , , , , , , , Subject: Re: [PATCH 3/3] KVM: arm/arm64: vgic: Don't rely on the wrong pending table In-Reply-To: <20191029071919.177-4-yuzenghui@huawei.com> References: <20191029071919.177-1-yuzenghui@huawei.com> <20191029071919.177-4-yuzenghui@huawei.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 91.217.168.176 X-SA-Exim-Rcpt-To: yuzenghui@huawei.com, eric.auger@redhat.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, wanghaibin.wang@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Oct 2019 07:19:19 +0000, 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. > > Signed-off-by: Zenghui Yu > --- > > If this patch has done the right thing, we can even add the: > > Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES") > > 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 pending > 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. > > I think I must have some misunderstanding here... Please fix me. I think you're spot on, and it is the code needs fixing, not you! The problem is that we only read a byte once, irrespective of the vcpu the interrupts is routed to. If we switch to another vcpu for the same byte offset, we must reload it. This can be done by either checking the vcpu, or by tracking the guest address that we read from (just like you do here). A small comment below: > virt/kvm/arm/vgic/vgic-v3.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > 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) > { > struct vgic_dist *dist = &kvm->arch.vgic; > - int last_byte_offset = -1; > struct vgic_irq *irq; > + gpa_t last_ptr = -1; This should be written as gpa_t last_ptr = ~(gpa_t)0; > int ret; > u8 val; > > @@ -384,11 +384,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm) > bit_nr = irq->intid % BITS_PER_BYTE; > ptr = pendbase + byte_offset; > > - if (byte_offset != last_byte_offset) { > + if (ptr != last_ptr) { > ret = kvm_read_guest_lock(kvm, ptr, &val, 1); > if (ret) > return ret; > - last_byte_offset = byte_offset; > + last_ptr = ptr; > } > > stored = val & (1U << bit_nr); Otherwise, this looks good to me (no need to respin for the above nit). Eric, can I get an Ack from you, since you write this code? Thanks, M. -- Jazz is not dead, it just smells funny. 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=-7.0 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 B2675CA9EAE for ; Tue, 29 Oct 2019 09:23:47 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 3EA1520830 for ; Tue, 29 Oct 2019 09:23:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3EA1520830 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B507B4A955; Tue, 29 Oct 2019 05:23:46 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8XbsLipB3pfa; Tue, 29 Oct 2019 05:23:45 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 9D0284A4A4; Tue, 29 Oct 2019 05:23:45 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id CBC7A4A4F6 for ; Tue, 29 Oct 2019 05:23:43 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id yGQ1Co3ryv1Q for ; Tue, 29 Oct 2019 05:23:42 -0400 (EDT) Received: from inca-roads.misterjones.org (inca-roads.misterjones.org [213.251.177.50]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id A3DD14A4A9 for ; Tue, 29 Oct 2019 05:23:42 -0400 (EDT) Received: from [91.217.168.176] (helo=big-swifty.misterjones.org) by cheepnis.misterjones.org with esmtpsa (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.80) (envelope-from ) id 1iPNj0-0005iM-ET; Tue, 29 Oct 2019 10:23:38 +0100 Date: Tue, 29 Oct 2019 09:23:37 +0000 Message-ID: <86mudjykfa.wl-maz@kernel.org> From: Marc Zyngier To: Zenghui Yu Subject: Re: [PATCH 3/3] KVM: arm/arm64: vgic: Don't rely on the wrong pending table In-Reply-To: <20191029071919.177-4-yuzenghui@huawei.com> References: <20191029071919.177-1-yuzenghui@huawei.com> <20191029071919.177-4-yuzenghui@huawei.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 91.217.168.176 X-SA-Exim-Rcpt-To: yuzenghui@huawei.com, eric.auger@redhat.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, wanghaibin.wang@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false Cc: linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tue, 29 Oct 2019 07:19:19 +0000, 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. > > Signed-off-by: Zenghui Yu > --- > > If this patch has done the right thing, we can even add the: > > Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES") > > 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 pending > 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. > > I think I must have some misunderstanding here... Please fix me. I think you're spot on, and it is the code needs fixing, not you! The problem is that we only read a byte once, irrespective of the vcpu the interrupts is routed to. If we switch to another vcpu for the same byte offset, we must reload it. This can be done by either checking the vcpu, or by tracking the guest address that we read from (just like you do here). A small comment below: > virt/kvm/arm/vgic/vgic-v3.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > 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) > { > struct vgic_dist *dist = &kvm->arch.vgic; > - int last_byte_offset = -1; > struct vgic_irq *irq; > + gpa_t last_ptr = -1; This should be written as gpa_t last_ptr = ~(gpa_t)0; > int ret; > u8 val; > > @@ -384,11 +384,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm) > bit_nr = irq->intid % BITS_PER_BYTE; > ptr = pendbase + byte_offset; > > - if (byte_offset != last_byte_offset) { > + if (ptr != last_ptr) { > ret = kvm_read_guest_lock(kvm, ptr, &val, 1); > if (ret) > return ret; > - last_byte_offset = byte_offset; > + last_ptr = ptr; > } > > stored = val & (1U << bit_nr); Otherwise, this looks good to me (no need to respin for the above nit). Eric, can I get an Ack from you, since you write this code? Thanks, M. -- Jazz is not dead, it just smells funny. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 1DC28CA9EC4 for ; Tue, 29 Oct 2019 09:23:46 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DD26520830 for ; 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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iPNj7-0005c2-Ep; Tue, 29 Oct 2019 09:23:45 +0000 Received: from inca-roads.misterjones.org ([213.251.177.50]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iPNj4-0005bJ-4C for linux-arm-kernel@lists.infradead.org; Tue, 29 Oct 2019 09:23:43 +0000 Received: from [91.217.168.176] (helo=big-swifty.misterjones.org) by cheepnis.misterjones.org with esmtpsa (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.80) (envelope-from ) id 1iPNj0-0005iM-ET; Tue, 29 Oct 2019 10:23:38 +0100 Date: Tue, 29 Oct 2019 09:23:37 +0000 Message-ID: <86mudjykfa.wl-maz@kernel.org> From: Marc Zyngier To: Zenghui Yu Subject: Re: [PATCH 3/3] KVM: arm/arm64: vgic: Don't rely on the wrong pending table In-Reply-To: <20191029071919.177-4-yuzenghui@huawei.com> References: <20191029071919.177-1-yuzenghui@huawei.com> <20191029071919.177-4-yuzenghui@huawei.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 91.217.168.176 X-SA-Exim-Rcpt-To: yuzenghui@huawei.com, eric.auger@redhat.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, wanghaibin.wang@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191029_022342_317488_2A0996EB X-CRM114-Status: GOOD ( 23.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: suzuki.poulose@arm.com, linux-kernel@vger.kernel.org, eric.auger@redhat.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, wanghaibin.wang@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 29 Oct 2019 07:19:19 +0000, 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. > > Signed-off-by: Zenghui Yu > --- > > If this patch has done the right thing, we can even add the: > > Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES") > > 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 pending > 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. > > I think I must have some misunderstanding here... Please fix me. I think you're spot on, and it is the code needs fixing, not you! The problem is that we only read a byte once, irrespective of the vcpu the interrupts is routed to. If we switch to another vcpu for the same byte offset, we must reload it. This can be done by either checking the vcpu, or by tracking the guest address that we read from (just like you do here). A small comment below: > virt/kvm/arm/vgic/vgic-v3.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > 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) > { > struct vgic_dist *dist = &kvm->arch.vgic; > - int last_byte_offset = -1; > struct vgic_irq *irq; > + gpa_t last_ptr = -1; This should be written as gpa_t last_ptr = ~(gpa_t)0; > int ret; > u8 val; > > @@ -384,11 +384,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm) > bit_nr = irq->intid % BITS_PER_BYTE; > ptr = pendbase + byte_offset; > > - if (byte_offset != last_byte_offset) { > + if (ptr != last_ptr) { > ret = kvm_read_guest_lock(kvm, ptr, &val, 1); > if (ret) > return ret; > - last_byte_offset = byte_offset; > + last_ptr = ptr; > } > > stored = val & (1U << bit_nr); Otherwise, this looks good to me (no need to respin for the above nit). Eric, can I get an Ack from you, since you write this code? Thanks, M. -- Jazz is not dead, it just smells funny. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel