From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1BCAA607B454 for ; Mon, 2 Nov 2026 14:54:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=k/0scAPB; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=NtQSE6Hg DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=3nu4A7upnl5Om0m7LZNGnD5TdTBPU65hBgFN+c/tzUc=; b=k/0scAPBhGyrHE tyKpLn6r+qVMxfl32bedazfD4g1lfQFvfHTFA4CzJ83pSdslouvYgao+1WxldhwkKok2+wBE4lmKJ jRFChDhNujr6EHU9xg8JobxN8d/LYksvOcYPEEuq+DIwCg/wwlWBWluOtinFUNJmcRRGdmjAzMIxy Jle7Z9V7/lsUwEW4/dW7LPNwIrpweNyXRouhhwDx9QO95btLWfNUuZJe4ZsDKavxD5P1hc4YvN09y vBVHsH7L6ey1z9LAa1+CWCwf6oHyVOq6Haulr/O/tkKnd/lRW0v91J1G/FjY9stLwX+zR1zWT6x0p bcvMiQ0NT7Lv5PQIezKg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xNtQe-0000000GvYH-0iUV; Mon, 02 Nov 2026 14:54:32 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xNtQY-0000000GvW1-33oy for linux-arm-kernel@lists.infradead.org; Mon, 02 Nov 2026 14:54:28 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7E35B1576; Mon, 2 Nov 2026 06:54:22 -0800 (PST) Received: from LeoBrasDK.cambridge.arm.com (LeoBrasDK.cambridge.arm.com [10.2.212.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E92D63F871; Mon, 2 Nov 2026 06:54:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793631265; bh=pe+eF55ZtCt9EK50Q3JeMHIuu3r98fGvy4S7dN+6afo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NtQSE6Hg4NZPFXQ1EiNFOU1PmKa4H+Hf6xPJvfcB7KdwuZLbI457GZl+8mrCNBtNo 2PyrOqZhuMSPZNmfOZxZdtkgpZkjgebncw8Do9WE4zg2AeHLkFeYCskOC/ovLTR/p3 5sUzDS++27WFhdVSSUC8oDy0ouhPtxEMyn5zal3U= From: Leonardo Bras To: Tian Zheng Cc: Leonardo Bras , maz@kernel.org, oupton@kernel.org, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, pbonzini@redhat.com, yuzenghui@huawei.com, wangzhou1@hisilicon.com, yangjinqian1@huawei.com, caijian11@h-partners.com, liuyonglong@huawei.com, tangchengchang@huawei.com, yezhenyu2@huawei.com, yubihong@huawei.com, linuxarm@huawei.com, joey.gouly@arm.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, seiden@linux.ibm.com, suzuki.poulose@arm.com, fuad.tabba@linux.dev, mark.rutland@arm.com, seanjc@google.com, rdunlap@infradead.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, skhan@linuxfoundation.org Subject: Re: [PATCH v5 11/15] KVM: arm64: Reserve dirty ring space for the HDBSS buffer Date: Mon, 2 Nov 2026 14:54:19 +0000 Message-ID: X-Mailer: git-send-email 2.56.0 In-Reply-To: <20260929103655.85107-12-zhengtian10@huawei.com> References: <20260929103655.85107-1-zhengtian10@huawei.com> <20260929103655.85107-12-zhengtian10@huawei.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261102_065426_825852_7D59C472 X-CRM114-Status: GOOD ( 19.13 ) X-Spam-Score: -4.4 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Sep 29, 2026 at 06:36:51PM +0800, Tian Zheng wrote: > The dirty ring reserves room for CPU-side dirty buffers via > kvm_cpu_dirty_log_size(). Report the HDBSS buffer entry count > through it, so a full buffer flush always fits in the ring. > > Pin the HDBSS buffer size to PAGE_SIZE when dirty-ring is enabled, > via kvm_arch_dirty_ring_size_updated(): a larger buffer only > shrinks the soft_limit and forces more frequent userspace drains. > > Signed-off-by: Tian Zheng > --- > arch/arm64/kvm/arm.c | 8 ++++++++ > arch/arm64/kvm/mmu.c | 8 ++++++++ > 2 files changed, 16 insertions(+) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 9d7bdece149a..5a7046acb62e 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -215,6 +215,14 @@ static int kvm_arm_default_max_vcpus(void) > return vgic_present ? kvm_vgic_get_max_vcpus() : KVM_MAX_VCPUS; > } > > +void kvm_arch_dirty_ring_size_updated(struct kvm *kvm) > +{ > + if (!system_supports_hdbss()) > + return; > + > + kvm->arch.hdbss_buffer_size = KVM_ARM_HDBSS_DEFAULT_SIZE; > +} > + On the same subject as a previous patch: I don't think this is the best approach, on top of adding a new weak function to take care. Maybe during the dirty-ring allocation, on vcpu creation, we could take into account the requested dirty-ring size, and just allocate the HDBSS buffer taking that into account. That would make it simpler, don't you agree? Thanks! Leo