Re: [Qemu-devel] [PATCH v3 19/29] postcopy: wake shared

[Peter Xu]

On Fri, Feb 16, 2018 at 01:16:15PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> Send a 'wake' request on a userfaultfd for a shared process.
> The address in the clients address space is specified together
> with the RAMBlock it was resolved to.

I think it's "providing a helper to send WAKE to uffd" rather than
really sending it.

Otherwise it looks good to me.  Thanks,

> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  migration/postcopy-ram.c | 26 ++++++++++++++++++++++++++
>  migration/postcopy-ram.h |  6 ++++++
>  migration/trace-events   |  1 +
>  3 files changed, 33 insertions(+)
> 
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 277ff749a0..67deae7e1c 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -534,6 +534,25 @@ static int ram_block_enable_notify(const char 
> *block_name, void *host_addr,
>      return 0;
>  }
>  
> +int postcopy_wake_shared(struct PostCopyFD *pcfd,
> +                         uint64_t client_addr,
> +                         RAMBlock *rb)
> +{
> +    size_t pagesize = qemu_ram_pagesize(rb);
> +    struct uffdio_range range;
> +    int ret;
> +    trace_postcopy_wake_shared(client_addr, qemu_ram_get_idstr(rb));
> +    range.start = client_addr & ~(pagesize - 1);
> +    range.len = pagesize;
> +    ret = ioctl(pcfd->fd, UFFDIO_WAKE, &range);
> +    if (ret) {
> +        error_report("%s: Failed to wake: %zx in %s (%s)",
> +                     __func__, (size_t)client_addr, qemu_ram_get_idstr(rb),
> +                     strerror(errno));
> +    }
> +    return ret;
> +}
> +
>  /*
>   * Callback from shared fault handlers to ask for a page,
>   * the page must be specified by a RAMBlock and an offset in that rb
> @@ -951,6 +970,13 @@ void *postcopy_get_tmp_page(MigrationIncomingState *mis)
>      return NULL;
>  }
>  
> +int postcopy_wake_shared(struct PostCopyFD *pcfd,
> +                         uint64_t client_addr,
> +                         RAMBlock *rb)
> +{
> +    assert(0);
> +    return -1;
> +}
>  #endif
>  
>  /* ------------------------------------------------------------------------- 
> */
> diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> index 4c63f20df4..2e3dd844d5 100644
> --- a/migration/postcopy-ram.h
> +++ b/migration/postcopy-ram.h
> @@ -162,6 +162,12 @@ struct PostCopyFD {
>   */
>  void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
>  void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
> +/* Notify a client ufd that a page is available
> + * Note: The 'client_address' is in the address space of the client
> + * program not QEMU
> + */
> +int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr,
> +                         RAMBlock *rb);
>  /* Callback from shared fault handlers to ask for a page */
>  int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
>                                   uint64_t client_addr, uint64_t offset);
> diff --git a/migration/trace-events b/migration/trace-events
> index 7c910b5479..b0acaaa8a0 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -199,6 +199,7 @@ postcopy_ram_incoming_cleanup_entry(void) ""
>  postcopy_ram_incoming_cleanup_exit(void) ""
>  postcopy_ram_incoming_cleanup_join(void) ""
>  postcopy_request_shared_page(const char *sharer, const char *rb, uint64_t 
> rb_offset) "for %s in %s offset 0x%"PRIx64
> +postcopy_wake_shared(uint64_t client_addr, const char *rb) "at 0x%"PRIx64" 
> in %s"
>  
>  save_xbzrle_page_skipping(void) ""
>  save_xbzrle_page_overflow(void) ""
> -- 
> 2.14.3
> 

-- 
Peter Xu