Re: [PATCH 2/2] hyperv/synic: Allocate as ram_device

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jan 08, 2020 at 01:53:53PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Mark the synic pages as ram_device so that they won't be visible
> to vhost.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


I think I disagree with this one.
 * A RAM device represents a mapping to a physical device, such as to a PCI
 * MMIO BAR of an vfio-pci assigned device.  The memory region may be mapped
 * into the VM address space and access to the region will modify memory
 * directly.  However, the memory region should not be included in a memory
 * dump (device may not be enabled/mapped at the time of the dump), and
 * operations incompatible with manipulating MMIO should be avoided.  Replaces
 * skip_dump flag.

Looks like an abuse of notation.



> ---
>  hw/hyperv/hyperv.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
> index da8ce82725..4de3ec411d 100644
> --- a/hw/hyperv/hyperv.c
> +++ b/hw/hyperv/hyperv.c
> @@ -95,12 +95,14 @@ static void synic_realize(DeviceState *dev, Error **errp)
>      msgp_name = g_strdup_printf("synic-%u-msg-page", vp_index);
>      eventp_name = g_strdup_printf("synic-%u-event-page", vp_index);
>  
> -    memory_region_init_ram(&synic->msg_page_mr, obj, msgp_name,
> -                           sizeof(*synic->msg_page), &error_abort);
> -    memory_region_init_ram(&synic->event_page_mr, obj, eventp_name,
> -                           sizeof(*synic->event_page), &error_abort);
> -    synic->msg_page = memory_region_get_ram_ptr(&synic->msg_page_mr);
> -    synic->event_page = memory_region_get_ram_ptr(&synic->event_page_mr);
> +    synic->msg_page = qemu_memalign(qemu_real_host_page_size,
> +                                    sizeof(*synic->msg_page));
> +    synic->event_page = qemu_memalign(qemu_real_host_page_size,
> +                                      sizeof(*synic->event_page));
> +    memory_region_init_ram_device_ptr(&synic->msg_page_mr, obj, msgp_name,
> +                           sizeof(*synic->msg_page), synic->msg_page);
> +    memory_region_init_ram_device_ptr(&synic->event_page_mr, obj, eventp_name,
> +                           sizeof(*synic->event_page), synic->event_page);
>  
>      g_free(msgp_name);
>      g_free(eventp_name);
> -- 
> 2.24.1