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=-8.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 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 E9B78C43331 for ; Tue, 31 Mar 2020 08:07:21 +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 C0284206F6 for ; Tue, 31 Mar 2020 08:07:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ix5p3ihq"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="UpShdRnj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0284206F6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jdOY3N3uPNsDhVOnNhO2T07D6acCDirkPOr3XPShUKg=; b=ix5p3ihq1dr/yt LnCRZxYUimOUjfub/ssGFwxIS0Z3a5iAloe/PBuputJNkqS/duQLxUaqAHREC5ske1mQM7fNvZ83b guADXpWE2KWHcKXK21au0YgEkscOV44PgmUUsRsVjHcFHcI8/YnIYlemH+qr0KvKm7OCkTEzyhOHu bHoVHYSoMYmy2r6r95b+Wa/T0PQcQrKEtPwrGSL7bqtGKmhATl26cT/61h58GsndQfwVOYpR3l0V3 HHYu3ksFb9iSmizG2L7CXdqkNeBfLlVdJm1XCAaskVp7S4M23gEZvXm5YEYEnJm+8ef+aX7BVd9TQ BxP8Bl5lcRH1od85fv5A==; 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 1jJBva-0005yi-Jp; Tue, 31 Mar 2020 08:07:18 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jJBvX-0005xk-DS for linux-arm-kernel@lists.infradead.org; Tue, 31 Mar 2020 08:07:16 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B7D09206F6; Tue, 31 Mar 2020 08:07:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585642033; bh=pR3KtS9JqxSwtoxlI+XX4Uem3z/HcC5CN+Wr9J/Rekc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=UpShdRnjDu/kmIuKs89/r7lQiwaTpOxhwEmaJs7lpMZHTQnNgqbdTu6hLdxMd5cSf rUrj1KwPVPB8loOZlZxt13HURDwSwcZL+jZ6qisDn4NvI4BpFecTIzKjtbRk+Fp4xi ojOj2Y/dah/9X7NNozyrA7rzRnLRfZzniOmHE+W8= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jJBvT-00H774-TH; Tue, 31 Mar 2020 09:07:12 +0100 Date: Tue, 31 Mar 2020 09:07:09 +0100 From: Marc Zyngier To: Zenghui Yu Subject: Re: [PATCH] KVM: arm64: vgic-v3: Clear pending bit in guest memory after synchronization Message-ID: <20200331090709.17d2087d@why> In-Reply-To: <20200331031245.1562-1-yuzenghui@huawei.com> References: <20200331031245.1562-1-yuzenghui@huawei.com> Organization: Approximate X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: yuzenghui@huawei.com, kvmarm@lists.cs.columbia.edu, eric.auger@redhat.com, andre.przywara@arm.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, wanghaibin.wang@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200331_010715_491647_CC6C09A0 X-CRM114-Status: GOOD ( 21.67 ) 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, andre.przywara@arm.com, linux-kernel@vger.kernel.org, eric.auger@redhat.com, james.morse@arm.com, linux-arm-kernel@lists.infradead.org, wanghaibin.wang@huawei.com, kvmarm@lists.cs.columbia.edu, julien.thierry.kdev@gmail.com 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 Hi Zenghui, On Tue, 31 Mar 2020 11:12:45 +0800 Zenghui Yu wrote: > When LPI support is enabled at redistributor level, VGIC will potentially > load the correspond LPI penging table and sync it into the pending_latch. > To avoid keeping the 'consumed' pending bits lying around in guest memory > (though they're not used), let's clear them after synchronization. > > The similar work had been done in vgic_v3_lpi_sync_pending_status(). > > Signed-off-by: Zenghui Yu > --- > virt/kvm/arm/vgic/vgic-its.c | 23 +++++++++++++++++------ > 1 file changed, 17 insertions(+), 6 deletions(-) > > diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c > index d53d34a33e35..905760bfa404 100644 > --- a/virt/kvm/arm/vgic/vgic-its.c > +++ b/virt/kvm/arm/vgic/vgic-its.c > @@ -435,6 +435,7 @@ static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu) > > for (i = 0; i < nr_irqs; i++) { > int byte_offset, bit_nr; > + bool status; > > byte_offset = intids[i] / BITS_PER_BYTE; > bit_nr = intids[i] % BITS_PER_BYTE; > @@ -447,22 +448,32 @@ static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu) > ret = kvm_read_guest_lock(vcpu->kvm, > pendbase + byte_offset, > &pendmask, 1); > - if (ret) { > - kfree(intids); > - return ret; > - } > + if (ret) > + goto out; > last_byte_offset = byte_offset; > } > > + status = pendmask & (1 << bit_nr); > + > irq = vgic_get_irq(vcpu->kvm, NULL, intids[i]); > raw_spin_lock_irqsave(&irq->irq_lock, flags); > - irq->pending_latch = pendmask & (1U << bit_nr); > + irq->pending_latch = status; > vgic_queue_irq_unlock(vcpu->kvm, irq, flags); > vgic_put_irq(vcpu->kvm, irq); > + > + if (status) { > + /* clear consumed data */ > + pendmask &= ~(1 << bit_nr); > + ret = kvm_write_guest_lock(vcpu->kvm, > + pendbase + byte_offset, > + &pendmask, 1); > + if (ret) > + goto out; > + } > } > > +out: > kfree(intids); > - > return ret; > } > I've been thinking about this, and I wonder why we don't simply clear the whole pending table instead of carefully wiping it one bit at a time. My reasoning is that if a LPI isn't mapped, then it cannot be made pending the first place. And I think there is a similar issue in vgic_v3_lpi_sync_pending_status(). Why sync something back from the pending table when the LPI wasn't mapped yet? This seems pretty bizarre, as the GITS_TRANSLATER spec says that the write to this register is ignored when: "- The EventID is mapped to an Interrupt Translation Table and the EventID is within the range specified by MAPD on page 5-107, but the EventID is unmapped." (with the added bonus in the form of a type: the first instance of "EventID" here should obviously be "DeviceID"). What do you think? 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