From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793631266; b=4+cu+xKSTknYMpmNCiWNDrOLLrLUO7UreUi1LyfHseNzsbCkVFwMmD5mPDoO94DPL32B S+hsMWlnqyaWIHbyqkv/kF4dk/dFxvohLYFasfggp8n8wyEeKGRyVf5Z3HlV/si3fJxqh yO+WTq/MWYigRpaWNP6jGGNT13l4AgGjAi9Oqpw8teA1T8GJo4RtIkVu1oBf7AOm23CBi bS9ycl5wqLMXLeAcwIvVz/uhI9BUtxFdW+NHiDL1gT2YfcxcsDs2bKEaYTLciffrzaSRn Xhl93u04/eBbR5poWNnrUXa65upzpgdlmPLWRx8+hs5iOwkDUZrqNRRzZshlBgkIaiw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793631266; h=DMARC-Filter:Received:Received:DKIM-Signature:From:To:Cc:Subject: Date:Message-ID:X-Mailer:In-Reply-To:References:MIME-Version: Content-Type:Content-Disposition:Content-Transfer-Encoding; bh=3nu4A7upnl5Om0m7LZNGnD5TdTBPU65hBgFN+c/tzUc=; b=O+MvTh+NY63/JVVbOWHUGS4QUm7HE+3pM6WxolTK7/whNId7MzNb5uTW+Kfk1EQXbStA xJhuJQR8TFogJwpGhsxcweNopKDjmlN4262i4+KWnapKvjSHudA38tZ0d5VXAUDzjfzyt pFE5ED/RJ/YTMYkpxO5oyBV/zsq4NU6Rywkho8RxJTCR7LqQtXXN8T9epxOywB9IMAqD3 ho6C3w8LELPb2C08wYswn2IuHu+a1jPkeG8Tj0cd5F/a7p82v+hJYDtO62Bo8ncWNmSe2 x/4Ke2O8oOI3PwAi4Kyi66z+P919O5zuAVzP03zY2IQ3NQvqMeRvWCHItbQFar6JPmA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=NtQSE6Hg; arc=none smtp.remote-ip=217.140.110.172 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4B261606A589; Mon, 2 Nov 2026 14:54:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 4B261606A589 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=NtQSE6Hg 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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8bit 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