Re: [QEMU][PATCHv2 3/8] xen: add pseudo RAM region for grant mappings

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 25 Oct 2023, Vikram Garhwal wrote:
> From: Juergen Gross <jgross@xxxxxxxx>
> 
> Add a memory region which can be used to automatically map granted
> memory. It is starting at 0x8000000000000000ULL in order to be able to
> distinguish it from normal RAM.
> 
> For this reason the xen.ram memory region is expanded, which has no
> further impact as it is used just as a container of the real RAM
> regions and now the grant region.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  hw/i386/xen/xen-hvm.c           |  3 +++
>  hw/xen/xen-hvm-common.c         |  4 ++--
>  hw/xen/xen-mapcache.c           | 27 +++++++++++++++++++++++++++
>  include/hw/xen/xen-hvm-common.h |  2 ++
>  include/hw/xen/xen_pvdev.h      |  3 +++
>  include/sysemu/xen-mapcache.h   |  3 +++
>  6 files changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
> index f42621e674..67a55558a6 100644
> --- a/hw/i386/xen/xen-hvm.c
> +++ b/hw/i386/xen/xen-hvm.c
> @@ -172,6 +172,9 @@ static void xen_ram_init(PCMachineState *pcms,
>                                   x86ms->above_4g_mem_size);
>          memory_region_add_subregion(sysmem, 0x100000000ULL, &ram_hi);
>      }
> +
> +    /* Add grant mappings as a pseudo RAM region. */
> +    ram_grants = *xen_init_grant_ram();
>  }
>  
>  static XenPhysmap *get_physmapping(hwaddr start_addr, ram_addr_t size)
> diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
> index 565dc39c8f..b7255977a5 100644
> --- a/hw/xen/xen-hvm-common.c
> +++ b/hw/xen/xen-hvm-common.c
> @@ -9,7 +9,7 @@
>  #include "hw/boards.h"
>  #include "hw/xen/arch_hvm.h"
>  
> -MemoryRegion ram_memory;
> +MemoryRegion ram_memory, ram_grants;
>  
>  void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr,
>                     Error **errp)
> @@ -26,7 +26,7 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, 
> MemoryRegion *mr,
>          return;
>      }
>  
> -    if (mr == &ram_memory) {
> +    if (mr == &ram_memory || mr == &ram_grants) {
>          return;
>      }
>  
> diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
> index f7d974677d..8115c44c00 100644
> --- a/hw/xen/xen-mapcache.c
> +++ b/hw/xen/xen-mapcache.c
> @@ -14,7 +14,9 @@
>  
>  #include <sys/resource.h>
>  
> +#include "hw/xen/xen-hvm-common.h"
>  #include "hw/xen/xen_native.h"
> +#include "hw/xen/xen_pvdev.h"
>  #include "qemu/bitmap.h"
>  
>  #include "sysemu/runstate.h"
> @@ -597,3 +599,28 @@ uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
>      mapcache_unlock();
>      return p;
>  }
> +
> +MemoryRegion *xen_init_grant_ram(void)
> +{
> +    RAMBlock *block;
> +
> +    memory_region_init(&ram_grants, NULL, "xen.grants",
> +                       XEN_MAX_VIRTIO_GRANTS * XC_PAGE_SIZE);
> +    block = g_malloc0(sizeof(*block));
> +    block->mr = &ram_grants;
> +    block->used_length = XEN_MAX_VIRTIO_GRANTS * XC_PAGE_SIZE;
> +    block->max_length = XEN_MAX_VIRTIO_GRANTS * XC_PAGE_SIZE;
> +    block->fd = -1;
> +    block->page_size = XC_PAGE_SIZE;
> +    block->host = (void *)XEN_GRANT_ADDR_OFF;
> +    block->offset = XEN_GRANT_ADDR_OFF;
> +    block->flags = RAM_PREALLOC;
> +    ram_grants.ram_block = block;
> +    ram_grants.ram = true;
> +    ram_grants.terminates = true;
> +    ram_block_add_list(block);
> +    memory_region_add_subregion(get_system_memory(), XEN_GRANT_ADDR_OFF,
> +                                &ram_grants);
> +
> +    return &ram_grants;
> +}
> diff --git a/include/hw/xen/xen-hvm-common.h b/include/hw/xen/xen-hvm-common.h
> index 4e9904f1a6..0d300ba898 100644
> --- a/include/hw/xen/xen-hvm-common.h
> +++ b/include/hw/xen/xen-hvm-common.h
> @@ -17,6 +17,8 @@
>  #include <xen/hvm/ioreq.h>
>  
>  extern MemoryRegion ram_memory;
> +
> +extern MemoryRegion ram_grants;
>  extern MemoryListener xen_io_listener;
>  extern DeviceListener xen_device_listener;
>  
> diff --git a/include/hw/xen/xen_pvdev.h b/include/hw/xen/xen_pvdev.h
> index ddad4b9f36..0f1b5edfa9 100644
> --- a/include/hw/xen/xen_pvdev.h
> +++ b/include/hw/xen/xen_pvdev.h
> @@ -80,4 +80,7 @@ int xen_pv_send_notify(struct XenLegacyDevice *xendev);
>  void xen_pv_printf(struct XenLegacyDevice *xendev, int msg_level,
>                     const char *fmt, ...)  G_GNUC_PRINTF(3, 4);
>  
> +#define XEN_GRANT_ADDR_OFF    0x8000000000000000ULL
> +#define XEN_MAX_VIRTIO_GRANTS 65536
> +
>  #endif /* QEMU_HW_XEN_PVDEV_H */
> diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h
> index c8e7c2f6cf..f4bedb1c11 100644
> --- a/include/sysemu/xen-mapcache.h
> +++ b/include/sysemu/xen-mapcache.h
> @@ -10,6 +10,7 @@
>  #define XEN_MAPCACHE_H
>  
>  #include "exec/cpu-common.h"
> +#include "exec/ram_addr.h"
>  
>  typedef hwaddr (*phys_offset_to_gaddr_t)(hwaddr phys_offset,
>                                           ram_addr_t size);
> @@ -25,6 +26,8 @@ void xen_invalidate_map_cache(void);
>  uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
>                                   hwaddr new_phys_addr,
>                                   hwaddr size);
> +MemoryRegion *xen_init_grant_ram(void);
> +
>  #else
>  
>  static inline void xen_map_cache_init(phys_offset_to_gaddr_t f,
> -- 
> 2.17.1
>