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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 743A7CA1016 for ; Mon, 8 Sep 2025 16:57:17 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uvf8m-0006qp-AT; Mon, 08 Sep 2025 12:54:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uvf8Y-0006e9-2A for qemu-devel@nongnu.org; Mon, 08 Sep 2025 12:54:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uvf8N-0001ag-Q7 for qemu-devel@nongnu.org; Mon, 08 Sep 2025 12:54:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757350465; 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=Yy0UHB5UY3SkW0YZ23dbCFp+M/mYAit6r4Hadl6Hdj8=; b=KtWwaAmPqhwUzm5YWH/lL3fJrBjRvdEObq2GXyeSXupvrJNHd1+t1sNCOh3te1ptZW1reY hUwsGp39zEYnPIByairwAFguw/cBHaMVt8kZpPAff9KkBKgVSvEeBwmMFCnqvDC6Iyb/rz +STWuMMzzHkuL/I4ZV0h2zDyhkmhCzU= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-367-z690hmoZPVWCDC8iA0nOFQ-1; Mon, 08 Sep 2025 12:54:24 -0400 X-MC-Unique: z690hmoZPVWCDC8iA0nOFQ-1 X-Mimecast-MFC-AGG-ID: z690hmoZPVWCDC8iA0nOFQ_1757350463 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6D9BD1800365; Mon, 8 Sep 2025 16:54:23 +0000 (UTC) Received: from corto.redhat.com (unknown [10.44.32.50]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id CBC99300018D; Mon, 8 Sep 2025 16:54:21 +0000 (UTC) From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= To: qemu-devel@nongnu.org Cc: Alex Williamson , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= , Yi Liu Subject: [PULL 08/31] vfio: Report an error when the 'dma_max_mappings' limit is reached Date: Mon, 8 Sep 2025 18:53:31 +0200 Message-ID: <20250908165354.1731444-9-clg@redhat.com> In-Reply-To: <20250908165354.1731444-1-clg@redhat.com> References: <20250908165354.1731444-1-clg@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The VFIO IOMMU Type1 kernel driver enforces a default IOMMU mapping limit of 65535, which is configurable via the 'dma_max_mappings' module parameter. When this limit is reached, QEMU issues a warning and fails the mapping operation, but allows the VM to continue running, potentially causing issues later. This scenario occurs with SEV-SNP guests, which must update all IOMMU mappings during initialization. To address this, update vfio_ram_discard_register_listener() to accept an 'Error **' parameter and propagate the error to the caller. This change will halt the VM immediately, at init time, with the same error message. Additionally, the same behavior will be enforced at runtime. While this might be considered too brutal, the rarity of this case and the planned removal of the dma_max_mappings module parameter make it a reasonable approach. Cc: Alex Williamson Reviewed-by: Yi Liu Reviewed-by: Alex Williamson Link: https://lore.kernel.org/qemu-devel/20250814153419.1643897-1-clg@redhat.com Signed-off-by: Cédric Le Goater --- hw/vfio/listener.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c index 5ebafaa07ea15070dfbe299d3f2c0f265959fb7d..c244be5e218ae60e2b9c8a29d2d4b9dad86fc77a 100644 --- a/hw/vfio/listener.c +++ b/hw/vfio/listener.c @@ -250,8 +250,9 @@ static int vfio_ram_discard_notify_populate(RamDiscardListener *rdl, return 0; } -static void vfio_ram_discard_register_listener(VFIOContainerBase *bcontainer, - MemoryRegionSection *section) +static bool vfio_ram_discard_register_listener(VFIOContainerBase *bcontainer, + MemoryRegionSection *section, + Error **errp) { RamDiscardManager *rdm = memory_region_get_ram_discard_manager(section->mr); int target_page_size = qemu_target_page_size(); @@ -316,13 +317,15 @@ static void vfio_ram_discard_register_listener(VFIOContainerBase *bcontainer, if (vrdl_mappings + max_memslots - vrdl_count > bcontainer->dma_max_mappings) { - warn_report("%s: possibly running out of DMA mappings. E.g., try" + error_setg(errp, "%s: possibly running out of DMA mappings. E.g., try" " increasing the 'block-size' of virtio-mem devies." " Maximum possible DMA mappings: %d, Maximum possible" " memslots: %d", __func__, bcontainer->dma_max_mappings, max_memslots); + return false; } } + return true; } static void vfio_ram_discard_unregister_listener(VFIOContainerBase *bcontainer, @@ -571,7 +574,9 @@ void vfio_container_region_add(VFIOContainerBase *bcontainer, */ if (memory_region_has_ram_discard_manager(section->mr)) { if (!cpr_remap) { - vfio_ram_discard_register_listener(bcontainer, section); + if (!vfio_ram_discard_register_listener(bcontainer, section, &err)) { + goto fail; + } } else if (!vfio_cpr_ram_discard_register_listener(bcontainer, section)) { error_setg(&err, -- 2.51.0