dom0/pvh: fix processing softirqs during memory map population

Make sure softirqs are processed after every successful call to
guest_physmap_add_page. Even if only a single page is to be added,
it's unknown whether the p2m or the IOMMU will require splitting the
provided page into smaller ones, and thus in case of having to break
a 1G page into 4K entries the amount of time taken by a single of
those additions will be non-trivial. Stay on the safe side and check
for pending softirqs on every successful loop iteration.

Fixes: 5427134eae ('x86: populate PVHv2 Dom0 physical memory map')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index afba6e7dfdf465ddcfc8b42955af312ed990701f..f9e17249dcdaa440cb48cdd28edbad8b5351a13d 100644 (file)
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -113,10 +113,9 @@ static int __init pvh_populate_memory_range(struct domain *d,
         { .align = PFN_DOWN(MB(2)), .order = PAGE_ORDER_2M },
         { .align = PFN_DOWN(KB(4)), .order = PAGE_ORDER_4K },
     };
-    unsigned int max_order = MAX_ORDER, i = 0;
+    unsigned int max_order = MAX_ORDER;
     struct page_info *page;
     int rc;
-#define MAP_MAX_ITER 64
 
     while ( nr_pages != 0 )
     {
@@ -185,12 +184,16 @@ static int __init pvh_populate_memory_range(struct domain *d,
         start += 1UL << order;
         nr_pages -= 1UL << order;
         order_stats[order]++;
-        if ( (++i % MAP_MAX_ITER) == 0 )
-            process_pending_softirqs();
+        /*
+         * Process pending softirqs on every successful loop: it's unknown
+         * whether the p2m/IOMMU code will have split the page into multiple
+         * smaller entries, and thus the time consumed would be much higher
+         * than populating a single entry.
+         */
+        process_pending_softirqs();
     }
 
     return 0;
-#undef MAP_MAX_ITER
 }
 
 /* Steal RAM from the end of a memory region. */