Re: [Xen-devel] [PATCH 4/5] libxc/arm: allocate xenstore and console pages

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 27 Jun 2012, Ian Campbell wrote:
> On Tue, 2012-06-26 at 19:05 +0100, Stefano Stabellini wrote:
> > On Tue, 26 Jun 2012, Ian Campbell wrote:
> > > On Fri, 2012-06-22 at 17:09 +0100, Stefano Stabellini wrote:
> > > > Allocate two additional pages at the end of the guest physical memory
> > > > for xenstore and console.
> > > > Set HVM_PARAM_STORE_PFN and HVM_PARAM_CONSOLE_PFN to the corresponding
> > > > values.
> > > > 
> > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > > ---
> > > >  tools/libxc/xc_dom_arm.c |   32 ++++++++++++++++++++++----------
> > > >  1 files changed, 22 insertions(+), 10 deletions(-)
> > > > 
> > > > diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
> > > > index bb86139..df2eefe 100644
> > > > --- a/tools/libxc/xc_dom_arm.c
> > > > +++ b/tools/libxc/xc_dom_arm.c
> > > > @@ -25,6 +25,10 @@
> > > >  #include "xg_private.h"
> > > >  #include "xc_dom.h"
> > > >  
> > > > +#define NR_MAGIC_PAGES 2
> > > > +#define CONSOLE_PFN_OFFSET 0
> > > > +#define XENSTORE_PFN_OFFSET 1
> > > > +
> > > >  /* 
> > > > ------------------------------------------------------------------------
> > > >  */
> > > >  /*
> > > >   * arm guests are hybrid and start off with paging disabled, therefore 
> > > > no
> > > > @@ -47,12 +51,6 @@ static int setup_pgtables_arm(struct xc_dom_image 
> > > > *dom)
> > > >  static int alloc_magic_pages(struct xc_dom_image *dom)
> > > >  {
> > > >      DOMPRINTF_CALLED(dom->xch);
> > > > -    /* XXX
> > > > -     *   dom->p2m_guest
> > > > -     *   dom->start_info_pfn
> > > > -     *   dom->xenstore_pfn
> > > > -     *   dom->console_pfn
> > > > -     */
> > > >      return 0;
> > > >  }
> > > >  
> > > > @@ -127,18 +125,19 @@ int arch_setup_meminit(struct xc_dom_image *dom)
> > > >  {
> > > >      int rc;
> > > >      xen_pfn_t pfn, allocsz, i;
> > > > +    xen_pfn_t store_pfn, console_pfn;
> > > >  
> > > >      fprintf(stderr, "%s: tot pages %"PRI_xen_pfn" rambase 
> > > > %"PRI_xen_pfn"\n", __func__,
> > > >              dom->total_pages, dom->rambase_pfn);
> > > >  
> > > >      dom->shadow_enabled = 1;
> > > >  
> > > > -    dom->p2m_host = xc_dom_malloc(dom, sizeof(xen_pfn_t) * 
> > > > dom->total_pages);
> > > > +    dom->p2m_host = xc_dom_malloc(dom, sizeof(xen_pfn_t) * 
> > > > (dom->total_pages + NR_MAGIC_PAGES));
> > > >  
> > > >      fprintf(stderr, "%s: setup p2m from %"PRI_xen_pfn" for 
> > > > %"PRI_xen_pfn" pages\n", __func__,
> > > >              dom->rambase_pfn, dom->total_pages );
> > > >      /* setup initial p2m */
> > > > -    for ( pfn = 0; pfn < dom->total_pages; pfn++ )
> > > > +    for ( pfn = 0; pfn < (dom->total_pages + NR_MAGIC_PAGES); pfn++ )
> > > >          dom->p2m_host[pfn] = pfn + dom->rambase_pfn;
> > > >  
> > > >      fprintf(stderr, "%s: init'd p2m_host[0] = %"PRI_xen_pfn"\n", 
> > > > __func__, dom->p2m_host[0]);
> > > > @@ -148,10 +147,10 @@ int arch_setup_meminit(struct xc_dom_image *dom)
> > > >  
> > > >      /* allocate guest memory */
> > > >      for ( i = rc = allocsz = 0;
> > > > -          (i < dom->total_pages) && !rc;
> > > > +          (i < dom->total_pages + NR_MAGIC_PAGES) && !rc;
> > > >            i += allocsz )
> > > >      {
> > > > -        allocsz = dom->total_pages - i;
> > > > +        allocsz = (dom->total_pages + NR_MAGIC_PAGES) - i;
> > > 
> > > All these "+ NR_MAGIC_PAGES" are a bit troublesome looking.
> > > 
> > > Do these pages need to be in p2m_host or would it be fine to just insert
> > > them into the guest p2m individually outside the main allocation logic?
> > 
> > I think it makes sense for them to be in p2m_host. In fact if we try to
> > allocate them later, wouldn't we have the problem of having to extend
> > the guest p2m? We might as well do it here.
> 
> The actual guest p2m is internal to the hypervisor so we never see it at
> the tools layer.
> 
> I'm unsure if we need these magic pages in p2m_host. If we remember the
> gfn of the magic pages that's just as useful as remembering the offset
> in p2m_host and using p2m_host[offset]?

I think that you are right: it is better not to add them to p2m_host.

---

libxc/arm: allocate xenstore and console pages

Allocate two additional pages at the end of the guest physical memory
for xenstore and console.
Set HVM_PARAM_STORE_PFN and HVM_PARAM_CONSOLE_PFN to the corresponding
values.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
index bb86139..724e7ad 100644
--- a/tools/libxc/xc_dom_arm.c
+++ b/tools/libxc/xc_dom_arm.c
@@ -25,6 +25,10 @@
 #include "xg_private.h"
 #include "xc_dom.h"
 
+#define NR_MAGIC_PAGES 2
+#define CONSOLE_PFN_OFFSET 0
+#define XENSTORE_PFN_OFFSET 1
+
 /* ------------------------------------------------------------------------ */
 /*
  * arm guests are hybrid and start off with paging disabled, therefore no
@@ -46,13 +50,33 @@ static int setup_pgtables_arm(struct xc_dom_image *dom)
 
 static int alloc_magic_pages(struct xc_dom_image *dom)
 {
+    int rc, i, allocsz;
+    xen_pfn_t store_pfn, console_pfn, p2m[NR_MAGIC_PAGES];
+
     DOMPRINTF_CALLED(dom->xch);
-    /* XXX
-     *   dom->p2m_guest
-     *   dom->start_info_pfn
-     *   dom->xenstore_pfn
-     *   dom->console_pfn
-     */
+
+    for (i = 0; i < NR_MAGIC_PAGES; i++)
+        p2m[i] = dom->rambase_pfn + dom->total_pages + i;
+
+    for ( i = rc = allocsz = 0;
+          (i < NR_MAGIC_PAGES) && !rc;
+          i += allocsz) {
+        allocsz = NR_MAGIC_PAGES - i;
+        rc = xc_domain_populate_physmap_exact(
+                dom->xch, dom->guest_domid, allocsz,
+                0, 0, &p2m[i]);
+    }
+
+    console_pfn = dom->rambase_pfn + dom->total_pages + CONSOLE_PFN_OFFSET;
+    store_pfn = dom->rambase_pfn + dom->total_pages + XENSTORE_PFN_OFFSET;
+
+    xc_clear_domain_page(dom->xch, dom->guest_domid, console_pfn);
+    xc_clear_domain_page(dom->xch, dom->guest_domid, store_pfn);
+    xc_set_hvm_param(dom->xch, dom->guest_domid, HVM_PARAM_CONSOLE_PFN,
+            console_pfn);
+    xc_set_hvm_param(dom->xch, dom->guest_domid, HVM_PARAM_STORE_PFN,
+            store_pfn);
+
     return 0;
 }
 

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