Re: [PATCH qemu] Support grant references in mapping

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Jan 07, 2011 at 05:09:40PM -0500, Daniel De Graaf wrote:
> This is untested in qemu, but is the same patch as was applied to the
> server I have tested. It applies to the ioemu-remote that I am using.

I lost track of this patchset. I think we need to first have somebody
familiar with QEMU review these patches.

CC-ing Stefano, Ian, Anthony
> 
> ---
> 
> Request and support using grant references in backends for
> the keyboard and framebuffer.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> 
> ---
> 
> diff --git a/hw/xenfb.c b/hw/xenfb.c
> index 97960ba..c8d7a3e 100644
> --- a/hw/xenfb.c
> +++ b/hw/xenfb.c
> @@ -61,6 +61,7 @@ struct common {
>      struct XenDevice  xendev;  /* must be first */
>      void              *page;
>      DisplayState      *ds;
> +    int               uses_gref;
>  };
>  
>  struct XenInput {
> @@ -100,22 +101,27 @@ struct XenFB {
>  
>  static int common_bind(struct common *c)
>  {
> -    int mfn;
> +    int ref;
>  
> -    if (xenstore_read_fe_int(&c->xendev, "page-ref", &mfn) == -1)
> -	return -1;
>      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,
> -				   XC_PAGE_SIZE,
> -				   PROT_READ | PROT_WRITE, mfn);
> +    if (xenstore_read_fe_int(&c->xendev, "page-gref", &ref) == 0) {
> +	c->page = xc_gnttab_map_grant_ref(xen_xc, c->xendev.gnttabdev, c->xendev.dom, ref, PROT_READ | PROT_WRITE);
> +	c->uses_gref = 1;
> +    } else if (xenstore_read_fe_int(&c->xendev, "page-ref", &ref) == 0) {
> +	xen_pfn_t pfn = ref;
> +	c->page = xc_map_foreign_pages(xen_xc, c->xendev.dom, PROT_READ | PROT_WRITE, &pfn, 1);
> +	c->uses_gref = 0;
> +    } else
> +	return -1;
> +
>      if (c->page == NULL)
>  	return -1;
>  
>      xen_be_bind_evtchn(&c->xendev);
> -    xen_be_printf(&c->xendev, 1, "ring mfn %d, remote-port %d, local-port %d\n",
> -		  mfn, c->xendev.remote_port, c->xendev.local_port);
> +    xen_be_printf(&c->xendev, 1, "ring ref %d, remote-port %d, local-port %d\n",
> +		  ref, c->xendev.remote_port, c->xendev.local_port);
>  
>      return 0;
>  }
> @@ -123,10 +129,12 @@ static int common_bind(struct common *c)
>  static void common_unbind(struct common *c)
>  {
>      xen_be_unbind_evtchn(&c->xendev);
> -    if (c->page) {
> +    if (c->page && c->uses_gref) {
> +	xc_gnttab_munmap(xen_xc, c->xendev.gnttabdev, c->page, 1);
> +    } else if (c->page) {
>  	munmap(c->page, XC_PAGE_SIZE);
> -	c->page = NULL;
>      }
> +    c->page = NULL;
>  }
>  
>  /* -------------------------------------------------------------------- */
> @@ -422,8 +430,6 @@ static int xenfb_map_fb(struct XenFB *xenfb)
>      struct xenfb_page *page = xenfb->c.page;
>      char *protocol = xenfb->c.xendev.protocol;
>      int n_fbdirs;
> -    unsigned long *pgmfns = NULL;
> -    unsigned long *fbmfns = NULL;
>      void *map, *pd;
>      int mode, ret = -1;
>  
> @@ -472,36 +478,72 @@ static int xenfb_map_fb(struct XenFB *xenfb)
>  #endif
>      }
>  
> -    if (xenfb->pixels) {
> +    if (xenfb->pixels && xenfb->c.uses_gref) {
> +	xc_gnttab_munmap(xen_xc, xenfb->c.xendev.gnttabdev, xenfb->pixels, xenfb->fbpages);
> +    } else if (xenfb->pixels) {
>          munmap(xenfb->pixels, xenfb->fbpages * XC_PAGE_SIZE);
> -        xenfb->pixels = NULL;
>      }
> +    xenfb->pixels = NULL;
>  
>      xenfb->fbpages = (xenfb->fb_len + (XC_PAGE_SIZE - 1)) / XC_PAGE_SIZE;
>      n_fbdirs = xenfb->fbpages * mode / 8;
>      n_fbdirs = (n_fbdirs + (XC_PAGE_SIZE - 1)) / XC_PAGE_SIZE;
>  
> -    pgmfns = qemu_mallocz(sizeof(unsigned long) * n_fbdirs);
> -    fbmfns = qemu_mallocz(sizeof(unsigned long) * xenfb->fbpages);
> +    if (xenfb->c.uses_gref) {
> +	uint32_t* domids = qemu_mallocz(sizeof(uint32_t)*n_fbdirs);
> +	uint32_t* refs = qemu_mallocz(sizeof(uint32_t)*n_fbdirs);
> +	int i;
> +	for(i=0; i < n_fbdirs; i++)
> +	{
> +	    domids[i] = xenfb->c.xendev.dom;
> +	    refs[i] = (mode == 32) ? ((uint32_t*)pd)[i] : ((uint64_t*)pd)[i];
> +	}
>  
> -    xenfb_copy_mfns(mode, n_fbdirs, pgmfns, pd);
> -    map = xc_map_foreign_pages(xen_xc, 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);
> +	map = xc_gnttab_map_grant_refs(xen_xc, xenfb->c.xendev.gnttabdev,
> +	                               n_fbdirs, domids, refs, PROT_READ);
> +	qemu_free(domids);
> +	qemu_free(refs);
> +
> +	if (map == NULL)
> +	    goto out;
> +
> +	domids = qemu_mallocz(sizeof(uint32_t)*xenfb->fbpages);
> +	refs = qemu_mallocz(sizeof(uint32_t)*xenfb->fbpages);
> +	for(i=0; i < xenfb->fbpages; i++)
> +	{
> +	    domids[i] = xenfb->c.xendev.dom;
> +	    refs[i] = (mode == 32) ? ((uint32_t*)map)[i] : ((uint64_t*)map)[i];
> +	}
> +
> +	xc_gnttab_munmap(xen_xc, xenfb->c.xendev.gnttabdev, map, n_fbdirs);
> +	xenfb->pixels = xc_gnttab_map_grant_refs(xen_xc, xenfb->c.xendev.gnttabdev,
> +				xenfb->fbpages, domids, refs, PROT_READ);
> +	qemu_free(domids);
> +	qemu_free(refs);
> +    } else {
> +	unsigned long *pgmfns = qemu_mallocz(sizeof(unsigned long) * n_fbdirs);
> +	xenfb_copy_mfns(mode, n_fbdirs, pgmfns, pd);
> +	map = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
> +				   PROT_READ, pgmfns, n_fbdirs);
> +	qemu_free(pgmfns);
> +
> +	if (map == NULL)
> +	    goto out;
> +
> +	unsigned long *fbmfns = qemu_mallocz(sizeof(unsigned long) * xenfb->fbpages);
> +	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,
> +					     PROT_READ | PROT_WRITE, fbmfns, xenfb->fbpages);
> +	qemu_free(fbmfns);
> +    }
>  
> -    xenfb->pixels = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
> -					 PROT_READ | PROT_WRITE, fbmfns, xenfb->fbpages);
>      if (xenfb->pixels == NULL)
>  	goto out;
>  
>      ret = 0; /* all is fine */
>  
>  out:
> -    qemu_free(pgmfns);
> -    qemu_free(fbmfns);
>      return ret;
>  }
>  
> @@ -860,6 +902,8 @@ static int fb_init(struct XenDevice *xendev)
>  #ifdef XENFB_TYPE_RESIZE
>      xenstore_write_be_int(xendev, "feature-resize", 1);
>  #endif
> +    xenstore_write_be_int(xendev, "use-grants", 1);
> +
>      return 0;
>  }
>  
> @@ -913,6 +957,13 @@ static void fb_disconnect(struct XenDevice *xendev)
>  {
>      struct XenFB *fb = container_of(xendev, struct XenFB, c.xendev);
>  
> +    if (fb->pixels && fb->c.uses_gref) {
> +	xc_gnttab_munmap(xen_xc, fb->c.xendev.gnttabdev, fb->pixels, fb->fbpages);
> +    } else if (fb->pixels) {
> +	// Note: not needed if we are doing the mmap() below
> +	// munmap(fb->pixels, fb->fbpages * XC_PAGE_SIZE);
> +    }
> +
>      /*
>       * FIXME: qemu can't un-init gfx display (yet?).
>       *   Replacing the framebuffer with anonymous shared memory
> 
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