Re: [Xen-devel] [PATCH 13/21] xenstored: use grant references instead of map_foreign_range

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-01-20 at 20:47 +0000, Daniel De Graaf wrote:
> From: Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>
> 
> make xenstored use grantref rather than map_foreign_range (which can
> only be used by privileged domains)
> 
> This patch modifies the xenstore daemon to use xc_gnttab_map_grant_ref
> instead of xc_map_foreign_range where available.
> 
> Previous versions of this patch have been sent to xen-devel. See
> http://lists.xensource.com/archives/html/xen-devel/2008-07/msg00610.html
> http://lists.xensource.com/archives/html/xen-devel/2009-03/msg01492.html
> 
> Signed-off-by: Diego Ongaro <diego.ongaro@xxxxxxxxxx>
> Signed-off-by: Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> ---
>  tools/xenstore/xenstored_domain.c |   52 ++++++++++++++++++++++++++++++++----
>  1 files changed, 46 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/xenstore/xenstored_domain.c 
> b/tools/xenstore/xenstored_domain.c
> index 443af82..661d955 100644
> --- a/tools/xenstore/xenstored_domain.c
> +++ b/tools/xenstore/xenstored_domain.c
> @@ -32,8 +32,10 @@
>  #include "xenstored_watch.h"
>  
>  #include <xenctrl.h>
> +#include <xen/grant_table.h>
>  
>  static xc_interface **xc_handle;
> +static xc_gnttab **xcg_handle;
>  static evtchn_port_t virq_port;
>  
>  xc_evtchn *xce_handle = NULL;
> @@ -163,6 +165,26 @@ static int readchn(struct connection *conn, void *data, 
> unsigned int len)
>       return len;
>  }
>  
> +static void *map_interface(domid_t domid, unsigned long mfn)
> +{
> +     if (*xcg_handle >= 0) {
> +             /* this is the preferred method */
> +             return xc_gnttab_map_grant_ref(*xcg_handle, domid,
> +                     GNTTAB_RESERVED_XENSTORE, PROT_READ|PROT_WRITE);
> +     } else {
> +             return xc_map_foreign_range(*xc_handle, domid,
> +                     getpagesize(), PROT_READ|PROT_WRITE, mfn);
> +     }
> +}
> +
> +static void unmap_interface(void *interface)
> +{
> +     if (*xcg_handle >= 0)
> +             xc_gnttab_munmap(*xcg_handle, interface, 1);
> +     else
> +             munmap(interface, getpagesize());
> +}
> +
>  static int destroy_domain(void *_domain)
>  {
>       struct domain *domain = _domain;
> @@ -174,8 +196,12 @@ static int destroy_domain(void *_domain)
>                       eprintf("> Unbinding port %i failed!\n", domain->port);
>       }
>  
> -     if (domain->interface)
> -             munmap(domain->interface, getpagesize());
> +     if (domain->interface) {
> +             if (domain->domid == 0)
> +                     munmap(domain->interface, getpagesize());
> +             else
> +                     unmap_interface(domain->interface);
> +     }
>  
>       fire_watches(NULL, "@releaseDomain", false);
>  
> @@ -344,9 +370,7 @@ void do_introduce(struct connection *conn, struct 
> buffered_data *in)
>       domain = find_domain_by_domid(domid);
>  
>       if (domain == NULL) {
> -             interface = xc_map_foreign_range(
> -                     *xc_handle, domid,
> -                     getpagesize(), PROT_READ|PROT_WRITE, mfn);
> +             interface = map_interface(domid, mfn);
>               if (!interface) {
>                       send_error(conn, errno);
>                       return;
> @@ -354,7 +378,7 @@ void do_introduce(struct connection *conn, struct 
> buffered_data *in)
>               /* Hang domain off "in" until we're finished. */
>               domain = new_domain(in, domid, port);
>               if (!domain) {
> -                     munmap(interface, getpagesize());
> +                     unmap_interface(interface);
>                       send_error(conn, errno);
>                       return;
>               }
> @@ -552,6 +576,12 @@ static int close_xc_handle(void *_handle)
>       return 0;
>  }
>  
> +static int close_xcg_handle(void *_handle)
> +{
> +     xc_gnttab_close(*(xc_gnttab **)_handle);
> +     return 0;
> +}
> +
>  /* Returns the implicit path of a connection (only domains have this) */
>  const char *get_implicit_path(const struct connection *conn)
>  {
> @@ -603,6 +633,16 @@ void domain_init(void)
>  
>       talloc_set_destructor(xc_handle, close_xc_handle);
>  
> +     xcg_handle = talloc(talloc_autofree_context(), xc_gnttab*);
> +     if (!xcg_handle)
> +             barf_perror("Failed to allocate domain gnttab handle");
> +
> +     *xcg_handle = xc_gnttab_open(NULL, 0);
> +     if (*xcg_handle < 0)
> +             xprintf("WARNING: Failed to open connection to gnttab\n");
> +     else
> +             talloc_set_destructor(xcg_handle, close_xcg_handle);
> +
>       xce_handle = xc_evtchn_open(NULL, 0);
>  
>       if (xce_handle == NULL)



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel