Re: [PATCH v4 27/27] hw/virtio/virtio-pci: Remove VIRTIO_PCI_FLAG_PAGE_PER_VQ definition

[Igor Mammedov <imammedo@redhat.com>]

On Thu,  8 May 2025 15:35:50 +0200
Philippe Mathieu-Daudé <philmd@linaro.org> wrote:

> VIRTIO_PCI_FLAG_PAGE_PER_VQ was only used by the hw_compat_2_7[]
> array, via the 'page-per-vq=on' property. We removed all
> machines using that array, lets remove all the code around
> VIRTIO_PCI_FLAG_PAGE_PER_VQ (see commit 9a4c0e220d8 for similar
> VIRTIO_PCI_FLAG_* enum removal).
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
> ---
>  include/hw/virtio/virtio-pci.h |  1 -
>  hw/display/virtio-vga.c        | 10 ----------
>  hw/virtio/virtio-pci.c         |  7 +------
>  3 files changed, 1 insertion(+), 17 deletions(-)
> 
> diff --git a/include/hw/virtio/virtio-pci.h b/include/hw/virtio/virtio-pci.h
> index 9838e8650a6..8abc5f8f20d 100644
> --- a/include/hw/virtio/virtio-pci.h
> +++ b/include/hw/virtio/virtio-pci.h
> @@ -33,7 +33,6 @@ enum {
>      VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT,
>      VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT,
>      VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT,
> -    VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT,

there is also 

/* page per vq flag to be used by split drivers within guests */                 
#define VIRTIO_PCI_FLAG_PAGE_PER_VQ \                                            
    (1 << VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT) 

left behind


nevertheless, I'm not sure if we should remove this at all,
it seems that there are external users
https://bugzilla.redhat.com/show_bug.cgi?id=1925363

>      VIRTIO_PCI_FLAG_ATS_BIT,
>      VIRTIO_PCI_FLAG_INIT_DEVERR_BIT,
>      VIRTIO_PCI_FLAG_INIT_LNKCTL_BIT,
> diff --git a/hw/display/virtio-vga.c b/hw/display/virtio-vga.c
> index 40e60f70fcd..83d01f089b5 100644
> --- a/hw/display/virtio-vga.c
> +++ b/hw/display/virtio-vga.c
> @@ -141,16 +141,6 @@ static void virtio_vga_base_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>                                 VIRTIO_GPU_SHM_ID_HOST_VISIBLE);
>      }
>  
> -    if (!(vpci_dev->flags & VIRTIO_PCI_FLAG_PAGE_PER_VQ)) {
> -        /*
> -         * with page-per-vq=off there is no padding space we can use
> -         * for the stdvga registers.  Make the common and isr regions
> -         * smaller then.
> -         */
> -        vpci_dev->common.size /= 2;
> -        vpci_dev->isr.size /= 2;
> -    }
> -
>      offset = memory_region_size(&vpci_dev->modern_bar);
>      offset -= vpci_dev->notify.size;
>      vpci_dev->notify.offset = offset;
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 7c965771907..4e0d4bda6ed 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -314,12 +314,9 @@ static bool virtio_pci_ioeventfd_enabled(DeviceState *d)
>      return (proxy->flags & VIRTIO_PCI_FLAG_USE_IOEVENTFD) != 0;
>  }
>  
> -#define QEMU_VIRTIO_PCI_QUEUE_MEM_MULT 0x1000
> -
>  static inline int virtio_pci_queue_mem_mult(struct VirtIOPCIProxy *proxy)
>  {
> -    return (proxy->flags & VIRTIO_PCI_FLAG_PAGE_PER_VQ) ?
> -        QEMU_VIRTIO_PCI_QUEUE_MEM_MULT : 4;
> +    return 4;
>  }
>  
>  static int virtio_pci_ioeventfd_assign(DeviceState *d, EventNotifier *notifier,
> @@ -2348,8 +2345,6 @@ static const Property virtio_pci_properties[] = {
>                      VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT, false),
>      DEFINE_PROP_BIT("modern-pio-notify", VirtIOPCIProxy, flags,
>                      VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT, false),
> -    DEFINE_PROP_BIT("page-per-vq", VirtIOPCIProxy, flags,
> -                    VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT, false),
>      DEFINE_PROP_BIT("ats", VirtIOPCIProxy, flags,
>                      VIRTIO_PCI_FLAG_ATS_BIT, false),
>      DEFINE_PROP_BIT("x-ats-page-aligned", VirtIOPCIProxy, flags,