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Re: [QEMU][PATCH v1 2/7] xen: add pseudo RAM region for grant mappings



On Thu, 5 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>

This patch doesn't apply to staging anymore


> ---
>  hw/i386/xen/xen-hvm.c           |  3 ++
>  hw/xen/xen-hvm-common.c         |  4 +--
>  hw/xen/xen-mapcache.c           | 27 ++++++++++++++
>  include/exec/ram_addr.h         |  1 +
>  include/hw/xen/xen-hvm-common.h |  2 ++
>  include/hw/xen/xen_pvdev.h      |  3 ++
>  include/sysemu/xen-mapcache.h   |  3 ++
>  softmmu/physmem.c               | 62 +++++++++++++++++++++------------
>  8 files changed, 80 insertions(+), 25 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;

It doesn't look like xen_init_grant_ram has anything to do with the
mapcache. It should be in another file. Maybe ./hw/xen/xen-hvm-common.c
or ./hw/i386/xen/xen-hvm.c (but this is x86 specific and we need grants
on ARM too)


> +}
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 90676093f5..c0b5f9a7d0 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -139,6 +139,7 @@ void qemu_ram_free(RAMBlock *block);
>  int qemu_ram_resize(RAMBlock *block, ram_addr_t newsize, Error **errp);
>  
>  void qemu_ram_msync(RAMBlock *block, ram_addr_t start, ram_addr_t length);
> +void ram_block_add_list(RAMBlock *new_block);
>  
>  /* Clear whole block of mem */
>  static inline void qemu_ram_block_writeback(RAMBlock *block)
> 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,
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index 309653c722..e182a2fa07 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c


You might want to split this change out of this patch to make it easier
to get the physmem.c maintainers' attention


> @@ -1803,12 +1803,47 @@ static void dirty_memory_extend(ram_addr_t 
> old_ram_size,
>      }
>  }
>  
> +static void ram_block_add_list_locked(RAMBlock *new_block)
> + {
> +     RAMBlock *block;
> +     RAMBlock *last_block = NULL;
> +
> +    /*
> +     * Keep the list sorted from biggest to smallest block.  Unlike QTAILQ,
> +     * QLIST (which has an RCU-friendly variant) does not have insertion at
> +     * tail, so save the last element in last_block.
> +     */
> +    RAMBLOCK_FOREACH(block) {
> +        last_block = block;
> +        if (block->max_length < new_block->max_length) {
> +            break;
> +        }
> +    }
> +    if (block) {
> +        QLIST_INSERT_BEFORE_RCU(block, new_block, next);
> +    } else if (last_block) {
> +        QLIST_INSERT_AFTER_RCU(last_block, new_block, next);
> +    } else { /* list is empty */
> +        QLIST_INSERT_HEAD_RCU(&ram_list.blocks, new_block, next);
> +    }
> +    ram_list.mru_block = NULL;
> +
> +    /* Write list before version */
> +    smp_wmb();
> +    ram_list.version++;
> +}
> +
> +void ram_block_add_list(RAMBlock *new_block)
> +{
> +    qemu_mutex_lock_ramlist();
> +    ram_block_add_list_locked(new_block);
> +    qemu_mutex_unlock_ramlist();
> +}
> +
>  static void ram_block_add(RAMBlock *new_block, Error **errp)
>  {
>      const bool noreserve = qemu_ram_is_noreserve(new_block);
>      const bool shared = qemu_ram_is_shared(new_block);
> -    RAMBlock *block;
> -    RAMBlock *last_block = NULL;
>      ram_addr_t old_ram_size, new_ram_size;
>      Error *err = NULL;
>  
> @@ -1846,28 +1881,9 @@ static void ram_block_add(RAMBlock *new_block, Error 
> **errp)
>      if (new_ram_size > old_ram_size) {
>          dirty_memory_extend(old_ram_size, new_ram_size);
>      }
> -    /* Keep the list sorted from biggest to smallest block.  Unlike QTAILQ,
> -     * QLIST (which has an RCU-friendly variant) does not have insertion at
> -     * tail, so save the last element in last_block.
> -     */
> -    RAMBLOCK_FOREACH(block) {
> -        last_block = block;
> -        if (block->max_length < new_block->max_length) {
> -            break;
> -        }
> -    }
> -    if (block) {
> -        QLIST_INSERT_BEFORE_RCU(block, new_block, next);
> -    } else if (last_block) {
> -        QLIST_INSERT_AFTER_RCU(last_block, new_block, next);
> -    } else { /* list is empty */
> -        QLIST_INSERT_HEAD_RCU(&ram_list.blocks, new_block, next);
> -    }
> -    ram_list.mru_block = NULL;
>  
> -    /* Write list before version */
> -    smp_wmb();
> -    ram_list.version++;
> +    ram_block_add_list_locked(new_block);
> +
>      qemu_mutex_unlock_ramlist();
>  
>      cpu_physical_memory_set_dirty_range(new_block->offset,
> -- 
> 2.17.1
> 



 


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