Re: Linux Stubdom Problem

[Jiageng Yu <yujiageng734@gmail.com>]

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2011/7/29 Stefano Stabellini <stefano.stabellini@eu.citrix.com>

> On Fri, 29 Jul 2011, Jiageng Yu wrote:
> > I have noticed the mistake. In fact, we shall stop the map_foreign_pages
> of xen_console and xenfb devices in qemu. Because
> > the front drivers in stubdom has already map the memories. This is my new
> patch. But it is not stable, I am testing it.
> >
> > We use xc_handle to map foreign pages in xenfb and xen_console devices.
> If qemu running on stubdom, the xc_handle is
> > invalid.
> >
> >
> > diff --git a/hw/xen_backend.c b/hw/xen_backend.c
> > index cfb53c8..11c53fe 100644
> > --- a/hw/xen_backend.c
> > +++ b/hw/xen_backend.c
> > @@ -47,6 +47,7 @@ XenXC xen_xc = XC_HANDLER_INITIAL_VALUE;
> >  XenGnttab xen_xcg = XC_HANDLER_INITIAL_VALUE;
> >  struct xs_handle *xenstore = NULL;
> >  const char *xen_protocol;
> > +XenXC xc_handle = XC_HANDLER_INITIAL_VALUE;
> >
> >  /* private */
> >  static QTAILQ_HEAD(XenDeviceHead, XenDevice) xendevs =
> QTAILQ_HEAD_INITIALIZER(xendevs);
> > @@ -655,6 +656,7 @@ static void xen_be_evtchn_event(void *opaque)
> >
> >  int xen_be_init(void)
> >  {
> > +#ifndef CONFIG_STUBDOM
> >      xenstore = xs_daemon_open();
> >      if (!xenstore) {
> >          xen_be_printf(NULL, 0, "can't connect to xenstored\n");
> > @@ -665,10 +667,16 @@ int xen_be_init(void)
> >          goto err;
> >      }
> >
> > +    if (xc_handle == XC_HANDLER_INITIAL_VALUE) {
> > +        goto err;
> > +    }
> > +#endif
> > +
> >      if (xen_xc == XC_HANDLER_INITIAL_VALUE) {
> >          /* Check if xen_init() have been called */
> >          goto err;
> >      }
> > +
> >      return 0;
> >
> >  err:
> > diff --git a/hw/xen_backend.h b/hw/xen_backend.h
> > index 9d36df3..bc5a157 100644
> > --- a/hw/xen_backend.h
> > +++ b/hw/xen_backend.h
> > @@ -59,6 +59,9 @@ extern XenXC xen_xc;
> >  extern struct xs_handle *xenstore;
> >  extern const char *xen_protocol;
> >
> > +/* invalid in linux stubdom */
> > +extern XenXC xc_handle;
> > +
> >  /* xenstore helper functions */
> >  int xenstore_write_str(const char *base, const char *node, const char
> *val);
> >  int xenstore_write_int(const char *base, const char *node, int ival);
> > diff --git a/hw/xen_console.c b/hw/xen_console.c
> > index c6c8163..66b6dd7 100644
> > --- a/hw/xen_console.c
> > +++ b/hw/xen_console.c
> > @@ -213,7 +213,7 @@ static int con_connect(struct XenDevice *xendev)
> >      if (xenstore_read_int(con->console, "limit", &limit) == 0)
> >   con->buffer.max_capacity = limit;
> >
> > -    con->sring = xc_map_foreign_range(xen_xc, con->xendev.dom,
> > +   con->sring = xc_map_foreign_range(xc_handle, con->xendev.dom,
> >            XC_PAGE_SIZE,
> >            PROT_READ|PROT_WRITE,
> >            con->ring_ref);
> > diff --git a/hw/xenfb.c b/hw/xenfb.c
> > index 039076a..278fa60 100644
> > --- a/hw/xenfb.c
> > +++ b/hw/xenfb.c
> > @@ -104,7 +104,7 @@ static int common_bind(struct common *c)
> >      if (xenstore_read_fe_int(&c->xendev, "event-channel",
> &c->xendev.remote_port) == -1)
> >   return -1;
> >
> > -    c->page = xc_map_foreign_range(xen_xc, c->xendev.dom,
> > +   c->page = xc_map_foreign_range(xc_handle, c->xendev.dom,
> >         XC_PAGE_SIZE,
> >         PROT_READ | PROT_WRITE, mfn);
> >      if (c->page == NULL)
> > @@ -482,14 +482,14 @@ static int xenfb_map_fb(struct XenFB *xenfb)
> >      fbmfns = qemu_mallocz(sizeof(unsigned long) * xenfb->fbpages);
> >
> >      xenfb_copy_mfns(mode, n_fbdirs, pgmfns, pd);
> > -    map = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
> > +   map = xc_map_foreign_pages(xc_handle, xenfb->c.xendev.dom,
> >            PROT_READ, pgmfns, n_fbdirs);
> >      if (map == NULL)
> >   goto out;
> >      xenfb_copy_mfns(mode, xenfb->fbpages, fbmfns, map);
> >      munmap(map, n_fbdirs * XC_PAGE_SIZE);
> >
> > -    xenfb->pixels = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
> > +   xenfb->pixels = xc_map_foreign_pages(xc_handle, xenfb->c.xendev.dom,
> >        PROT_READ | PROT_WRITE, fbmfns, xenfb->fbpages);
> >      if (xenfb->pixels == NULL)
> >   goto out;
> > diff --git a/xen-all.c b/xen-all.c
> > index b73fc43..04dfb51 100644
> > --- a/xen-all.c
> > +++ b/xen-all.c
> > @@ -527,12 +534,22 @@ int xen_init(void)
> >          return -1;
> >      }
> >
> > +#ifdef CONFIG_STUBDOM
> > +    return 0;
> > +#endif
> > +
> > +    xc_handle = xen_xc_interface_open(0, 0, 0);
> > +    if (xc_handle == XC_HANDLER_INITIAL_VALUE) {
> > +        xen_be_printf(NULL, 0, "can't open xen interface\n");
> > +        return -1;
> > +    }
> > +
> >      return 0;
> >  }
> >
> >
>
> I think that the backends shouldn't be initialized at all when running
> in the stubdom, so I would do something like this instead:
>
> diff --git a/xen-all.c b/xen-all.c
> index 167bed6..e3f630b 100644
> --- a/xen-all.c
> +++ b/xen-all.c
> @@ -922,6 +922,7 @@ int xen_hvm_init(void)
>     cpu_register_phys_memory_client(&state->client);
>     state->log_for_dirtybit = NULL;
>
> +#ifndef CONFIG_STUBDOM
>     /* Initialize backend core & drivers */
>     if (xen_be_init() != 0) {
>         fprintf(stderr, "%s: xen backend core setup failed\n",
> __FUNCTION__);
> @@ -930,7 +931,7 @@ int xen_hvm_init(void)
>     xen_be_register("console", &xen_console_ops);
>     xen_be_register("vkbd", &xen_kbdmouse_ops);
>     xen_be_register("qdisk", &xen_blkdev_ops);
> -
> +#endif
>     return 0;
>  }
>



Yes. this implementation of stubdom is more closer to the old qemu's
implementation. Which branch this patch works on? The qemu-dm-v15 would not
so lucky.

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