From mboxrd@z Thu Jan  1 00:00:00 1970
From: Razvan Cojocaru <rzvncj@gmail.com>
Subject: Multiple-page mem_event ring buffer?
Date: Tue, 05 Mar 2013 15:21:38 +0200
Message-ID: <5135F162.9060909@gmail.com>
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Hello,

currently my code (and all the examples I could find in the Xen source 
code) uses a single page mem_event ring buffer, using code along the 
lines of:

/* Map the ring page */
unsigned long ring_pfn;
xc_get_hvm_param(xci_, domain_, HVM_PARAM_ACCESS_RING_PFN, &ring_pfn);

unsigned long mmap_pfn = ring_pfn;
ringPage_ = xc_map_foreign_batch(xci_, domain_, PROT_READ | PROT_WRITE,
                                  &mmap_pfn, 1);

if (mmap_pfn & XEN_DOMCTL_PFINFO_XTAB) {

     /* Map failed, populate ring page */
     if (xc_domain_populate_physmap_exact(xci_, domain_,
                                          1, 0, 0, &ring_pfn))
         return SOME_ERROR;

     mmap_pfn = ring_pfn;
     ringPage = xc_map_foreign_batch(xci_, domain_,
                                     PROT_READ | PROT_WRITE,
                                     &mmap_pfn, 1);

     if (mmap_pfn & XEN_DOMCTL_PFINFO_XTAB)
         return SOME_OTHER ERROR;
}

Could I safely use more than one page for the ring buffer (passing '2' 
as the last parameter of xc_map_foreign_batch(), and so on), or am I 
limited to 1 page by design?


Thanks,
Razvan Cojocaru