{"id":2219886,"url":"http://patchwork.ozlabs.org/api/1.2/patches/2219886/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260405072857.66484-2-scottjgo@gmail.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.2/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260405072857.66484-2-scottjgo@gmail.com>","list_archive_url":null,"date":"2026-04-05T07:28:45","name":"[RFC,01/10] vfio/pci: Use the write side of EventNotifier for IRQ signaling","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"90f1afaaa053ab6afad7c3137510cf2be1ad1d16","submitter":{"id":93060,"url":"http://patchwork.ozlabs.org/api/1.2/people/93060/?format=json","name":"Scott J. Goldman","email":"scottjgo@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260405072857.66484-2-scottjgo@gmail.com/mbox/","series":[{"id":498765,"url":"http://patchwork.ozlabs.org/api/1.2/series/498765/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=498765","date":"2026-04-05T07:28:44","name":"vfio: PCI device passthrough on Apple Silicon Macs","version":1,"mbox":"http://patchwork.ozlabs.org/series/498765/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2219886/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2219886/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=RiNQvrvx;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fpPJq4SHjz1y2d\n\tfor ; Sun, 05 Apr 2026 17:31:07 +1000 (AEST)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1w9HvI-0003uO-Ks; Sun, 05 Apr 2026 03:29:32 -0400","from eggs.gnu.org ([2001:470:142:3::10])\n by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from )\n id 1w9HvG-0003ta-DK\n for qemu-devel@nongnu.org; Sun, 05 Apr 2026 03:29:30 -0400","from mail-dy1-x1330.google.com ([2607:f8b0:4864:20::1330])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128)\n (Exim 4.90_1) (envelope-from )\n id 1w9HvE-0007EY-LM\n for qemu-devel@nongnu.org; Sun, 05 Apr 2026 03:29:30 -0400","by mail-dy1-x1330.google.com with SMTP id\n 5a478bee46e88-2c54c68db4dso6147454eec.0\n for ; Sun, 05 Apr 2026 00:29:28 -0700 (PDT)","from localhost.localdomain ([2601:645:8200:47:41e4:ff2b:ff70:4d75])\n by smtp.gmail.com with ESMTPSA id\n 5a478bee46e88-2cb92ea0ef1sm7636502eec.21.2026.04.05.00.29.24\n (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256);\n Sun, 05 Apr 2026 00:29:25 -0700 (PDT)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed;\n d=gmail.com; s=20251104; t=1775374167; x=1775978967; darn=nongnu.org;\n h=content-transfer-encoding:mime-version:references:in-reply-to\n :message-id:date:subject:cc:to:from:from:to:cc:subject:date\n :message-id:reply-to;\n bh=o/AIm7dcgDves1AjHp0rGGsirlJpDLatrdTujVTNwp8=;\n b=RiNQvrvxM434JDdJoPHd1ljF5moiN3w0vLR/XMRwe149bL+yq35jB+VIz7ijyPJznt\n rlrDnrRRi0yAiJQ+fFV3QrHXAQ+8lNjNLvgZ9hgCUUCnCshaasXzwRFiQLYIZLrYCYFm\n dssnZwd5ZEDUidM13YhQTXyLgxRxuoTgX0AKqL0BqYJl3yWKpjevsZRjB7pfuLl+mav4\n 8utkZEaaz8RTYE6S3OmuQmlvvBaaEFdnBrKazcMNkJYxpbEMZ0MKcyWj0XpCiPhLcVCd\n OdfZI4RmmXPBlk6kX5wRZcw6OPdSNgFpm1gK3MAbCBZrZHA70R8vEhG3yJEIip0pJC42\n WTPA==","X-Google-DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed;\n d=1e100.net; s=20251104; t=1775374167; x=1775978967;\n h=content-transfer-encoding:mime-version:references:in-reply-to\n :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from\n :to:cc:subject:date:message-id:reply-to;\n bh=o/AIm7dcgDves1AjHp0rGGsirlJpDLatrdTujVTNwp8=;\n b=F+8bomq4UVfkLqBq2RdU89ycX6aW8j9lWG7IZk59A2MN86UGtJa12TON3uOd2uFBMY\n 4D5x85+X4ZGsphQqS8UfUAxRqygS/UlGrKltndqNjM6rMuB/tx70BuT1OpH21/QDwqV8\n pk/fJden+pzRJMmrwnk6/PrNbbMgiLAi7T2A2SO0FBxr4Twa145qJVxC8ayVR1FTrf4q\n q+utD1A/K48ynkaOfCGEDWCXmQSEGTYguSZxE239M3ANkQfV0NviR7QNAOW8pj18Vrqc\n /zb3QgtkuRFUKPTiI/0F6KEQhaRCuO5gxY+aPMhHFgCl0MKIBb6PVS79FniWsqEooS+v\n Dffg==","X-Gm-Message-State":"AOJu0YzqQJ1NNgH2NjyMl2V2E2mYJmxxhe/QSfYv0iSwZDP1gkFmfade\n pWoQm9MldPJro+ZTbxhe4cOTC77/h2CTKtIHmJnrv0Jx/g+Ohsu2vkvj9BvPvPWXQXQ=","X-Gm-Gg":"AeBDieuadQxAPfWjamKDQr98rz0Mk6vApArOeIjYmtFfOir0WApIfYh7YkqduKhgfar\n idBFHL/hlaSfeIIRKSmXBHe+yTR6RoV8rsa4sH1CXVme+q1142dFTXc3KglRPg3VnnoxfZVuMgo\n OYoTsh3WQK3rGC1AQq8eUSipMHVpvsHrC8FlNnFJgGA/E7/DZy7b9rH05vPrSxK4+3T7dMFWAX2\n 5McKCFyk88B83V6PYnA3jqoHrOHBliGoMEWPCgxSrpCfEgAdU1Tdlom3+OmvDzKE3RIcJ4kuHy+\n +kDwLaasrf4+XxvvxeZutUmRvoQzDZaP8KzizhaMAGHlTw2HqHboY0PxntNvKGnMlIo3Ho6Js70\n P/fGRdoqy56tKZ1nGLESShttt+92GoDP5yN2I/OuYs7FXjR5x8iA7tzLXG3kE00KzJHNZdtGqW2\n VFUYOY1d9wiD93IVKFt04geKa7CHw7rSqSBw2S6JxG9+qURN8gpNtb0MSPh9LQ54WEOseAcEj7g\n lcol44CmzZr9UnANj0BEec018I=","X-Received":"by 2002:a05:7300:571e:b0:2c4:4276:709f with SMTP id\n 5a478bee46e88-2cbf9afdabfmr4594191eec.1.1775374166740;\n Sun, 05 Apr 2026 00:29:26 -0700 (PDT)","From":"\"Scott J. Goldman\" ","To":"qemu-devel@nongnu.org","Cc":"alex@shazbot.org, clg@redhat.com, pbonzini@redhat.com, rbolshakov@ddn.com,\n phil@philjordan.eu, mst@redhat.com, john.levon@nutanix.com,\n thanos.makatos@nutanix.com, qemu-s390x@nongnu.org,\n \"Scott J. Goldman\" ","Subject":"[RFC PATCH 01/10] vfio/pci: Use the write side of EventNotifier for\n IRQ signaling","Date":"Sun, 5 Apr 2026 00:28:45 -0700","Message-ID":"<20260405072857.66484-2-scottjgo@gmail.com>","X-Mailer":"git-send-email 2.50.1","In-Reply-To":"<20260405072857.66484-1-scottjgo@gmail.com>","References":"<20260405072857.66484-1-scottjgo@gmail.com>","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","Received-SPF":"pass client-ip=2607:f8b0:4864:20::1330;\n envelope-from=scottjgo@gmail.com; helo=mail-dy1-x1330.google.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, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"When passing an fd to a vfio-user server for interrupt signaling, the\nwrite side of the EventNotifier must be used. For eventfd-backed\nnotifiers the read and write descriptors are the same, so the existing\nkernel VFIO path is unchanged. However, on hosts that emulate\nEventNotifier with a pipe pair (e.g. macOS), event_notifier_get_fd()\nreturns the read side, which the vfio-user server cannot write to.\n\nIntroduce vfio_irq_signal_fd() which returns event_notifier_get_wfd()\nand use it at every site in vfio/pci that hands an fd to\nvfio_device_irq_set_signaling() or the bulk IRQ path. The\nqemu_set_fd_handler() calls continue to use the read fd as before.\n\nSigned-off-by: Scott J. Goldman \n---\n hw/vfio/pci.c | 33 +++++++++++++++++++++++++--------\n 1 file changed, 25 insertions(+), 8 deletions(-)","diff":"diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c\nindex 1945751ffd..ee1a42e7e0 100644\n--- a/hw/vfio/pci.c\n+++ b/hw/vfio/pci.c\n@@ -80,6 +80,17 @@ static bool vfio_notifier_init(VFIOPCIDevice *vdev, EventNotifier *e,\n return true;\n }\n \n+/*\n+ * Return the fd that the vfio kernel driver or vfio-user server should\n+ * write to in order to signal an interrupt. For eventfd-backed notifiers\n+ * this is the same descriptor QEMU reads, but on hosts that emulate\n+ * EventNotifier with a pipe pair the write side must be used instead.\n+ */\n+static int vfio_irq_signal_fd(EventNotifier *e)\n+{\n+ return event_notifier_get_wfd(e);\n+}\n+\n static void vfio_notifier_cleanup(VFIOPCIDevice *vdev, EventNotifier *e,\n const char *name, int nr)\n {\n@@ -378,7 +389,9 @@ static bool vfio_intx_enable(VFIOPCIDevice *vdev, Error **errp)\n }\n \n if (!vfio_device_irq_set_signaling(&vdev->vbasedev, VFIO_PCI_INTX_IRQ_INDEX, 0,\n- VFIO_IRQ_SET_ACTION_TRIGGER, fd, errp)) {\n+ VFIO_IRQ_SET_ACTION_TRIGGER,\n+ vfio_irq_signal_fd(&vdev->intx.interrupt),\n+ errp)) {\n qemu_set_fd_handler(fd, NULL, NULL, vdev);\n vfio_notifier_cleanup(vdev, &vdev->intx.interrupt, \"intx-interrupt\", 0);\n return false;\n@@ -548,9 +561,9 @@ static int vfio_enable_vectors(VFIOPCIDevice *vdev, bool msix)\n if (vdev->msi_vectors[i].use) {\n if (vdev->msi_vectors[i].virq < 0 ||\n (msix && msix_is_masked(pdev, i))) {\n- fd = event_notifier_get_fd(&vdev->msi_vectors[i].interrupt);\n+ fd = vfio_irq_signal_fd(&vdev->msi_vectors[i].interrupt);\n } else {\n- fd = event_notifier_get_fd(&vdev->msi_vectors[i].kvm_interrupt);\n+ fd = vfio_irq_signal_fd(&vdev->msi_vectors[i].kvm_interrupt);\n }\n }\n \n@@ -628,9 +641,9 @@ static void set_irq_signalling(VFIODevice *vbasedev, VFIOMSIVector *vector,\n int32_t fd;\n \n if (vector->virq >= 0) {\n- fd = event_notifier_get_fd(&vector->kvm_interrupt);\n+ fd = vfio_irq_signal_fd(&vector->kvm_interrupt);\n } else {\n- fd = event_notifier_get_fd(&vector->interrupt);\n+ fd = vfio_irq_signal_fd(&vector->interrupt);\n }\n \n if (!vfio_device_irq_set_signaling(vbasedev, VFIO_PCI_MSIX_IRQ_INDEX, nr,\n@@ -770,7 +783,7 @@ static void vfio_msix_vector_release(PCIDevice *pdev, unsigned int nr)\n * be re-asserted on unmask. Nothing to do if already using QEMU mode.\n */\n if (vector->virq >= 0) {\n- int32_t fd = event_notifier_get_fd(&vector->interrupt);\n+ int32_t fd = vfio_irq_signal_fd(&vector->interrupt);\n Error *err = NULL;\n \n if (!vfio_device_irq_set_signaling(&vdev->vbasedev, VFIO_PCI_MSIX_IRQ_INDEX,\n@@ -3181,7 +3194,9 @@ void vfio_pci_register_err_notifier(VFIOPCIDevice *vdev)\n }\n \n if (!vfio_device_irq_set_signaling(&vdev->vbasedev, VFIO_PCI_ERR_IRQ_INDEX, 0,\n- VFIO_IRQ_SET_ACTION_TRIGGER, fd, &err)) {\n+ VFIO_IRQ_SET_ACTION_TRIGGER,\n+ vfio_irq_signal_fd(&vdev->err_notifier),\n+ &err)) {\n error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);\n qemu_set_fd_handler(fd, NULL, NULL, vdev);\n vfio_notifier_cleanup(vdev, &vdev->err_notifier, \"err_notifier\", 0);\n@@ -3254,7 +3269,9 @@ void vfio_pci_register_req_notifier(VFIOPCIDevice *vdev)\n }\n \n if (!vfio_device_irq_set_signaling(&vdev->vbasedev, VFIO_PCI_REQ_IRQ_INDEX, 0,\n- VFIO_IRQ_SET_ACTION_TRIGGER, fd, &err)) {\n+ VFIO_IRQ_SET_ACTION_TRIGGER,\n+ vfio_irq_signal_fd(&vdev->req_notifier),\n+ &err)) {\n error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);\n qemu_set_fd_handler(fd, NULL, NULL, vdev);\n vfio_notifier_cleanup(vdev, &vdev->req_notifier, \"req_notifier\", 0);\n","prefixes":["RFC","01/10"]}