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[2.214.8.136]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47fd458ab61sm25607861f8f.25.2026.08.02.10.41.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 Aug 2026 10:41:09 -0700 (PDT) From: Abhin Parekadan Jose To: mst@redhat.com, jasowangio@gmail.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Abhin Parekadan Jose Subject: [PATCH 1/2] virtio_pci_modern_dev: warn once on invalid status Date: Sun, 2 Aug 2026 17:40:58 +0000 Message-ID: <20260802174059.4082-2-abhinjoses@gmail.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20260802174059.4082-1-abhinjoses@gmail.com> References: <20260802174059.4082-1-abhinjoses@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" vp_modern_get_status() returns the raw device_status byte as read from the common configuration structure (struct virtio_pci_common_cfg, mapped via the VIRTIO_PCI_CAP_COMMON_CFG capability). That byte should only ever contain some combination of the status bits defined by the virtio spec (bits 0-3, 6-7); bits 4 and 5 are reserved and a spec-compliant device must never set them. A value with any other bit set means either the device is violating the spec, or the read never reached real device state at all -- e.g. because a write of 0x0000 to the PCI_COMMAND register (config space offset 4) clears the Memory Space Enable bit, causing the device to stop responding to memory-mapped register accesses -- effectively simulating an unresponsive/removed device without a real hot-unplug. In that case the MMIO read returns the bus's synthesized all-ones response instead of real device state. Add VIRTIO_STATUS_ERROR() to the uapi header to recognize such values, and warn once from vp_modern_get_status() when it sees one, so the bogus status is visible at its source rather than only showing up as confusing behavior in callers. Signed-off-by: Abhin Parekadan Jose --- drivers/virtio/virtio_pci_modern_dev.c | 8 +++++++- include/uapi/linux/virtio_config.h | 16 ++++++++++++++++ 2 files changed, 23 insertions(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio= _pci_modern_dev.c index 413a8c353463..60dd8acf1c28 100644 --- a/drivers/virtio/virtio_pci_modern_dev.c +++ b/drivers/virtio/virtio_pci_modern_dev.c @@ -480,8 +480,14 @@ EXPORT_SYMBOL_GPL(vp_modern_generation); u8 vp_modern_get_status(struct virtio_pci_modern_device *mdev) { struct virtio_pci_common_cfg __iomem *cfg =3D mdev->common; + u8 status =3D vp_ioread8(&cfg->device_status); =20 - return vp_ioread8(&cfg->device_status); + if (VIRTIO_STATUS_ERROR(status)) { + WARN_ONCE(1, "virtio: device returned error status: %#x\n", + status); + } + + return status; } EXPORT_SYMBOL_GPL(vp_modern_get_status); =20 diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio= _config.h index 2445f365bce7..6f458914c0ba 100644 --- a/include/uapi/linux/virtio_config.h +++ b/include/uapi/linux/virtio_config.h @@ -45,6 +45,22 @@ /* We've given up on this device. */ #define VIRTIO_CONFIG_S_FAILED 0x80 =20 +/* + * Check if a status value indicates an error + * All device_status bits currently defined by the virtio spec (bits + * 0,1,2,3,6,7). Bits 4 and 5 (0x10, 0x20) are reserved/undefined -- a + * real device must never set them. A status byte with any bit outside + * this mask set cannot be a legitimate value: either the device is + * violating the spec, or the read never actually reached it (e.g. + * PCI_COMMAND memory decode is disabled and this is a synthesized + * all-ones bus response instead of real device state). + */ +#define VIRTIO_STATUS_ERROR(val) \ + (((u8)(val)) & \ + ~(VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER | \ + VIRTIO_CONFIG_S_DRIVER_OK | VIRTIO_CONFIG_S_FEATURES_OK | \ + VIRTIO_CONFIG_S_NEEDS_RESET | VIRTIO_CONFIG_S_FAILED)) + /* * Virtio feature bits VIRTIO_TRANSPORT_F_START through * VIRTIO_TRANSPORT_F_END are reserved for the transport --=20 2.51.1 From nobody Fri Oct 2 10:07:34 2026 Received: from mail-wm1-f42.google.com (mail-wm1-f42.google.com [209.85.128.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 43D2130C177 for ; Sun, 2 Aug 2026 17:41:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.42 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785692477; cv=none; b=W1Wn+YJ79tECN0pqQ6872dY8cPYfFeAyGm4TWjpXPpGnUXQCBXACsqqaoOv5tqdWUV2PVfy8jDA/pNwyns2sE3Bfi9diJJgdUXVLJteqIY/AxKpMYcMYGXUxA7xjIc7bhqnTkQbJvg3y0wjEEqcNMPyWKCg+f4sGUzJ1UHI/BfA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785692477; c=relaxed/simple; bh=YTfmMGELnFD1PSu159ETFqwFo7TIsfNjR6vA/8zppps=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=incAbi7VZ06hU/V+MaGnknD6BCr2cASUCqTFKgN3DQyCXnklDcXQzdSzba7yTP0CZKQqwSNHHFqfGmshzAUJ4tYXGll8trJCQ0h/ZgcSZAn/McdnJByBpX5/9V1VEfDDJVlFl14r4GKlfpLBG9fqQo4PCtSkhZo/qTjQSuzOw/g= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=jyU3sA1R; arc=none smtp.client-ip=209.85.128.42 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jyU3sA1R" Received: by mail-wm1-f42.google.com with SMTP id 5b1f17b1804b1-49554ebb87dso11029385e9.3 for ; Sun, 02 Aug 2026 10:41:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785692474; x=1786297274; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=OhSlk96+XMRumlCtLR/Ln1APQ5h4yT2HFyCrvso93oY=; b=jyU3sA1RPVzNtp9InMar+DJP5rYkE+8eGmIoVFilBCm4bRwilMlc35K0DwdzjRWLSF Kp8VqbULsCt8HJ1mZs+5URsh9PavPU1DKBYUr04BHNOwaykculDys9Fx22bdyo0GryyA +NVJZwqdOXU0jvzC9Jqg1RpaRmAObuzxoVObSgmNswrKfdMvZxDfMcgRgkG5bYs8LnX2 coYTKwCjrK+8DqYJNDTCziLCBhNdUgaJ8w8CZB1AUSqtCRjlvLQYhXjKS9OW8Q/y5UHr TcQBbD1r7VDhupYXl1fZfsnVtvdoGtxoztFwHuzAJYlDzMt/IqguPKX0PRZTbZGImtn2 mHkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785692474; x=1786297274; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=OhSlk96+XMRumlCtLR/Ln1APQ5h4yT2HFyCrvso93oY=; b=GTP5HQfrIXAkXVMQgQVoEwGu+c3/lIYQ+9b4UQNQ2jImO5bSs8+JADpEzFfCT2YKAw 2KmhfUz14S3nLlb1FWi5azhGoqOJ7O6sLpA93k28Nu/knwpl6c3SQv271lj0bVZJNQ5u OEIHcB+dB/kDFpFx7FaK4ARVDBWJjTHlO9JDPZVLd42fSDN8CKVmlbfMDiinLbdSQ+Bc 4/CJ9KKU0izF1X/G8cHHmQ/v1mWJM60N0Z8s3/02e7FbwMWC+wWoCt8sLdm8qVZnvPoD hS4xNDXWOMABgjbhUdBYTODaKquRaJMzM+fVGpI8nVfKQEFpnVWFT4XoYO1xcskYclTS +0Fw== X-Forwarded-Encrypted: i=1; AHgh+Rqq5/4Bp4dkHJF9i1q2bTSOec2w8MaIE4fIlv2grfq3qlCdlgYBupCKDxL8Itt9aHkD14FnnrSv1wIlEzI=@vger.kernel.org X-Gm-Message-State: AOJu0Ywu9hgMtA2Vi13PqseHakEPFvcciMx3cce4NaQPH0OTZBJP48zr +FarseWg5GhD3xDFrkYAiTiBmtsRF8FqES7vTdYmebZE2jnCsV1Mcp16oOyRLveP X-Gm-Gg: AR+sD12Vysjrloj35OX0OeSH0SQZHT7hZp5p9tLfu3tsnEK4T6F94/B4NlGHNmofopV eVjuTNFgR9mI4eoaZmfOu4xVH9ECRl5u85Rc/Zd8sO+bs6tNBgWl8hURu7G/F7q66tPKHtXBVA3 eAUW+jZe4Bv8sI2/G/1KvnDhNBsTsfLTehYb9dD3puL3F3bJ6hPAxqgqZqUsM8gNTphLNEbrs+C QW8lNlpl5A805W9eiDyxgb26VI92PDC81QZlXu7kWCJaUueQ/s/UKxlD5TZ8f+wn25L3PCbYOV/ rRCn9s7cAUQHdyCX2El/S43VovBnM2vJS0v4pnysvyUvkklpYuATwGMAflO6his8kvJCk78Q8C9 Xe3VPPpieNoajVreIIufhgxUq1aJ8Lpx9rlCS3xyBtf9vCxaessJew4G6eNjH3/YPdRwlP95zGu tn6NG1FL3PkaQqZEhz0nOQ5jGWmMcz7TUIBTgnAtOtHCOv9XpJ9LbC/qOVIdn2+12MQ5qIZWCM8 uWwoj1CnfSUBkTMTyZ+ZiapCzWgKO2DZ3wLwm99tK78mBsDAbSdrDrWbWie/inX4VQ= X-Received: by 2002:a05:600c:354a:b0:495:4e89:3f30 with SMTP id 5b1f17b1804b1-4980c673874mr153659615e9.15.1785692474347; Sun, 02 Aug 2026 10:41:14 -0700 (PDT) Received: from a9d4faf53c34.fritz.box (dynamic-002-214-008-136.2.214.pool.telefonica.de. [2.214.8.136]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47fd458ab61sm25607861f8f.25.2026.08.02.10.41.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 Aug 2026 10:41:14 -0700 (PDT) From: Abhin Parekadan Jose To: mst@redhat.com, jasowangio@gmail.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Abhin Parekadan Jose Subject: [PATCH 2/2] virtio_pci_modern: avoid infinite loop in vp_reset() on invalid status Date: Sun, 2 Aug 2026 17:40:59 +0000 Message-ID: <20260802174059.4082-3-abhinjoses@gmail.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20260802174059.4082-1-abhinjoses@gmail.com> References: <20260802174059.4082-1-abhinjoses@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" vp_reset() polls device_status in a tight loop, waiting for it to read back as 0 after the reset write. device_status is read via MMIO from the common configuration structure, which requires the PCI_COMMAND Memory Space Enable bit to be set. If that bit is cleared while the device is bound -- e.g. by writing 0x0000 to PCI_COMMAND (config space offset 4) -- the MMIO read no longer reaches the device and returns the bus's synthesized all-ones response instead. Since that value can never legitimately clear to 0, the loop spins forever and hangs the caller. Use VIRTIO_STATUS_ERROR() to recognize such values and bail out of the poll loop instead of looping indefinitely. Signed-off-by: Abhin Parekadan Jose --- drivers/virtio/virtio_pci_modern.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci= _modern.c index 6d8ae2a6a8ca..209fa3b36c90 100644 --- a/drivers/virtio/virtio_pci_modern.c +++ b/drivers/virtio/virtio_pci_modern.c @@ -547,6 +547,7 @@ static void vp_reset(struct virtio_device *vdev) { struct virtio_pci_device *vp_dev =3D to_vp_device(vdev); struct virtio_pci_modern_device *mdev =3D &vp_dev->mdev; + u8 status; =20 /* 0 status means a reset. */ vp_modern_set_status(mdev, 0); @@ -555,8 +556,11 @@ static void vp_reset(struct virtio_device *vdev) * This will flush out the status write, and flush in device writes, * including MSI-X interrupts, if any. */ - while (vp_modern_get_status(mdev)) + while ((status =3D vp_modern_get_status(mdev))) { + if (VIRTIO_STATUS_ERROR(status)) + break; msleep(1); + } =20 vp_modern_avq_cleanup(vdev); =20 --=20 2.51.1