netdev - [PATCH v3 virtio 1/8] virtio: allow caller to override device id and DMA mask

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Message-ID: <20230322191038.44037-2-shannon.nelson@amd.com>
Date:   Wed, 22 Mar 2023 12:10:31 -0700
From:   Shannon Nelson <shannon.nelson@....com>
To:     <jasowang@...hat.com>, <mst@...hat.com>,
        <virtualization@...ts.linux-foundation.org>,
        <shannon.nelson@....com>, <brett.creeley@....com>,
        <davem@...emloft.net>, <netdev@...r.kernel.org>, <kuba@...nel.org>
CC:     <drivers@...sando.io>
Subject: [PATCH v3 virtio 1/8] virtio: allow caller to override device id and DMA mask

To allow a bit of flexibility with various virtio based devices, allow
the caller to specify a different device id and DMA mask.  This adds
fields to struct XXX to specify an override device id check and a DMA mask.

Signed-off-by: Shannon Nelson <shannon.nelson@....com>
---
 drivers/virtio/virtio_pci_modern_dev.c | 36 +++++++++++++++++---------
 include/linux/virtio_pci_modern.h      |  6 +++++
 2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index 869cb46bef96..6ad1bb9ae8fa 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c
@@ -221,18 +221,25 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 
 	check_offsets();
 
-	/* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
-	if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
-		return -ENODEV;
-
-	if (pci_dev->device < 0x1040) {
-		/* Transitional devices: use the PCI subsystem device id as
-		 * virtio device id, same as legacy driver always did.
-		 */
-		mdev->id.device = pci_dev->subsystem_device;
+	if (mdev->device_id_check_override) {
+		err = mdev->device_id_check_override(pci_dev);
+		if (err)
+			return err;
+		mdev->id.device = pci_dev->device;
 	} else {
-		/* Modern devices: simply use PCI device id, but start from 0x1040. */
-		mdev->id.device = pci_dev->device - 0x1040;
+		/* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
+		if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
+			return -ENODEV;
+
+		if (pci_dev->device < 0x1040) {
+			/* Transitional devices: use the PCI subsystem device id as
+			 * virtio device id, same as legacy driver always did.
+			 */
+			mdev->id.device = pci_dev->subsystem_device;
+		} else {
+			/* Modern devices: simply use PCI device id, but start from 0x1040. */
+			mdev->id.device = pci_dev->device - 0x1040;
+		}
 	}
 	mdev->id.vendor = pci_dev->subsystem_vendor;
 
@@ -260,7 +267,12 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 		return -EINVAL;
 	}
 
-	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
+	if (mdev->dma_mask_override)
+		err = dma_set_mask_and_coherent(&pci_dev->dev,
+						mdev->dma_mask_override);
+	else
+		err = dma_set_mask_and_coherent(&pci_dev->dev,
+						DMA_BIT_MASK(64));
 	if (err)
 		err = dma_set_mask_and_coherent(&pci_dev->dev,
 						DMA_BIT_MASK(32));
diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
index c4eeb79b0139..84765bbd8dc5 100644
--- a/include/linux/virtio_pci_modern.h
+++ b/include/linux/virtio_pci_modern.h
@@ -38,6 +38,12 @@ struct virtio_pci_modern_device {
 	int modern_bars;
 
 	struct virtio_device_id id;
+
+	/* alt. check for vendor virtio device, return 0 or -ERRNO */
+	int (*device_id_check_override)(struct pci_dev *pdev);
+
+	/* alt. mask for devices with limited DMA space */
+	u64 dma_mask_override;
 };
 
 /*
-- 
2.17.1