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    SubjectRe: [RFC PATCH 1/2] Add a new register offset let interrupt reason available
    On Sat, Oct 25, 2014 at 04:24:53PM +0800, john.liuli wrote:
    > From: Li Liu <john.liuli@huawei.com>
    >
    > Add a new register offset VIRTIO_MMIO_ISRMEM which help to
    > estblish a shared memory region between virtio-mmio driver
    > and qemu with two purposes:
    >
    > 1.Guest virtio-mmio driver can get the interrupt reason.
    > 2.Check irqfd enabled or not to register different irq handler.
    >
    > Signed-off-by: Li Liu <john.liuli@huawei.com>
    > ---
    > drivers/virtio/virtio_mmio.c | 21 ++++++++++++++++++++-
    > include/linux/virtio_mmio.h | 3 +++
    > 2 files changed, 23 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
    > index ef9a165..28ddb55 100644
    > --- a/drivers/virtio/virtio_mmio.c
    > +++ b/drivers/virtio/virtio_mmio.c
    > @@ -122,6 +122,8 @@ struct virtio_mmio_device {
    > /* a list of queues so we can dispatch IRQs */
    > spinlock_t lock;
    > struct list_head virtqueues;
    > +
    > + uint8_t *isr_mem;
    > };
    >
    > struct virtio_mmio_vq_info {
    > @@ -443,6 +445,7 @@ static int virtio_mmio_probe(struct platform_device *pdev)
    > struct virtio_mmio_device *vm_dev;
    > struct resource *mem;
    > unsigned long magic;
    > + int err;
    >
    > mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    > if (!mem)
    > @@ -481,6 +484,15 @@ static int virtio_mmio_probe(struct platform_device *pdev)
    > return -ENXIO;
    > }
    >
    > + vm_dev->isr_mem = alloc_pages_exact(PAGE_SIZE, GFP_KERNEL|__GFP_ZERO);
    > + if (vm_dev->isr_mem == NULL) {
    > + dev_err(&pdev->dev, "Allocate isr memory failed!\n");
    > + return -ENOMEM;
    > + }
    > +
    > + writel(virt_to_phys(vm_dev->isr_mem),
    > + vm_dev->base + VIRTIO_MMIO_ISRMEM);
    > +

    What happens to existing devices?
    then might not expect writes at this address.

    > vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);
    > vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);
    >
    > @@ -488,13 +500,20 @@ static int virtio_mmio_probe(struct platform_device *pdev)
    >
    > platform_set_drvdata(pdev, vm_dev);
    >
    > - return register_virtio_device(&vm_dev->vdev);
    > + err = register_virtio_device(&vm_dev->vdev);
    > + if (err) {
    > + free_pages_exact(vm_dev->isr_mem, PAGE_SIZE);
    > + vm_dev->isr_mem = NULL;
    > + }
    > +
    > + return err;
    > }
    >
    > static int virtio_mmio_remove(struct platform_device *pdev)
    > {
    > struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
    >
    > + free_pages_exact(vm_dev->isr_mem, PAGE_SIZE);
    > unregister_virtio_device(&vm_dev->vdev);
    >
    > return 0;
    > diff --git a/include/linux/virtio_mmio.h b/include/linux/virtio_mmio.h
    > index 5c7b6f0..b1e3ec7 100644
    > --- a/include/linux/virtio_mmio.h
    > +++ b/include/linux/virtio_mmio.h
    > @@ -95,6 +95,9 @@
    > /* Device status register - Read Write */
    > #define VIRTIO_MMIO_STATUS 0x070
    >
    > +/* Allocate ISRMEM for interrupt reason - Write Only */
    > +#define VIRTIO_MMIO_ISRMEM 0x080
    > +
    > /* The config space is defined by each driver as
    > * the per-driver configuration space - Read Write */
    > #define VIRTIO_MMIO_CONFIG 0x100
    > --
    > 1.7.9.5
    >


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