Re: [Xen-devel] [PATCH] qemu-xen-traditionnal, Fix dirty logging during migration.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 20 Jul 2012, Anthony PERARD wrote:
> This moves the xen_modified_memory call from cpu_physical_memory_map to
> cpu_physical_memory_unmap because the memory could be migrated before the
> device model have written to it.
> 
> The xen_ram_addr_from_mapcache function is imported from QEMU.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> 
> ---
>  hw/xen_machine_fv.c |   39 +++++++++++++++++++++++++++++++++++++++
>  i386-dm/exec-dm.c   |   10 ++++++----
>  qemu-xen.h          |    1 +
>  3 files changed, 46 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/xen_machine_fv.c b/hw/xen_machine_fv.c
> index fdad42a..c358944 100644
> --- a/hw/xen_machine_fv.c
> +++ b/hw/xen_machine_fv.c
> @@ -223,6 +223,45 @@ void qemu_invalidate_entry(uint8_t *buffer)
>      qemu_free(entry);
>  }
>  
> +target_phys_addr_t xen_ram_addr_from_mapcache(void *ptr)
> +{
> +    struct map_cache *entry = NULL;
> +    struct map_cache_rev *reventry;
> +    target_phys_addr_t paddr_index;
> +    int found = 0;
> +
> +    TAILQ_FOREACH(reventry, &locked_entries, next) {
> +        if (reventry->vaddr_req == ptr) {
> +            paddr_index = reventry->paddr_index;
> +            found = 1;
> +            break;
> +        }
> +    }
> +    if (!found) {
> +        fprintf(stderr, "%s, could not find %p\n", __func__, ptr);
> +        TAILQ_FOREACH(reventry, &locked_entries, next) {
> +            fprintf(stderr, "   %#10lx -> %p is present\n",
> +                    reventry->paddr_index,
> +                    reventry->vaddr_req);
> +        }
> +        abort();
> +        return 0;
> +    }
> +
> +    entry = &mapcache_entry[paddr_index % nr_buckets];
> +    while (entry && (entry->paddr_index != paddr_index)) {
> +        entry = entry->next;
> +    }
> +    if (!entry) {
> +        fprintf(stderr,
> +                "Trying to find address %p that is not in the mapcache!\n",
> +                ptr);
> +        return 0;
> +    }
> +    return (reventry->paddr_index << MCACHE_BUCKET_SHIFT) +
> +        ((unsigned long) ptr - (unsigned long) entry->vaddr_base);
> +}
> +
>  void qemu_invalidate_map_cache(void)
>  {
>      unsigned long i;
> diff --git a/i386-dm/exec-dm.c b/i386-dm/exec-dm.c
> index 96274d9..bf27a6a 100644
> --- a/i386-dm/exec-dm.c
> +++ b/i386-dm/exec-dm.c
> @@ -820,10 +820,6 @@ void *cpu_physical_memory_map(target_phys_addr_t addr,
>      if ((*plen) > l)
>          *plen = l;
>  #endif
> -    if (xen_logdirty_enable)
> -        xc_hvm_modified_memory(xc_handle, domid, addr >> TARGET_PAGE_BITS,
> -                ((addr + l + TARGET_PAGE_SIZE - 1) >> TARGET_PAGE_BITS)
> -                    - (addr >> TARGET_PAGE_BITS));
>  
>      return qemu_map_cache(addr, 1);
>  }
> @@ -835,6 +831,12 @@ void *cpu_physical_memory_map(target_phys_addr_t addr,
>  void cpu_physical_memory_unmap(void *buffer, target_phys_addr_t len,
>                                 int is_write, target_phys_addr_t access_len)
>  {
> +    if (xen_logdirty_enable && is_write) {
> +        target_phys_addr_t addr = xen_ram_addr_from_mapcache(buffer);
> +        xc_hvm_modified_memory(xc_handle, domid, addr >> TARGET_PAGE_BITS,
> +            ((addr + access_len + TARGET_PAGE_SIZE - 1) >> TARGET_PAGE_BITS)
> +                - (addr >> TARGET_PAGE_BITS));
> +    }
>      qemu_invalidate_entry(buffer);
>      cpu_notify_map_clients();
>  }

Considering that on qemu-xen-traditional there is just one caller of
qemu_invalidate_entry, that is cpu_physical_memory_unmap, we can just
add the xc_hvm_modified_memory call there and avoid introducing
xen_ram_addr_from_mapcache.

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