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Hi,
This patch provides a function which allows a domain to reclaim memory used by the allocate_empty_lowmem_region. It should allow a module to reclaim any memory which was released to Xen for foreign grant table access.
Thanks
Ross
# HG changeset patch
# User rcmcilro@xxxxxxxxxxxxxxxxxxxxx
# Node ID a05f92511a995c6ad48e5d508260edc756d4f327
# Parent 7c05931c1d0b82babd600b7e3e712fc06b899ed9
Functions to allow unallocation of memory regions created by allocate_empty_lowmem_region
Signed-of-by: Ross McIlroy <mcilrorc@xxxxxxxxxxxxx>
diff -r 7c05931c1d0b -r a05f92511a99 linux-2.6-xen-sparse/arch/xen/i386/mm/hypervisor.c
--- a/linux-2.6-xen-sparse/arch/xen/i386/mm/hypervisor.c Thu Aug 18 13:26:50 2005
+++ b/linux-2.6-xen-sparse/arch/xen/i386/mm/hypervisor.c Mon Aug 22 09:50:48 2005
@@ -452,7 +452,50 @@
return vstart;
}
+int unallocate_empty_lowmem_region(unsigned long vstart,
+ unsigned long pages)
+{
+ unsigned long *pfn_array;
+ unsigned long i;
+ unsigned int order = get_order(pages*PAGE_SIZE);
+ int err;
+
+ if (vstart == 0)
+ return -EINVAL;
+
+ pfn_array = vmalloc((1<<order) * sizeof(*pfn_array));
+ BUG_ON(pfn_array == NULL);
+
+ if (err = balloon_get_pages(pfn_array, 1 << order)) {
+ vfree(pfn_array);
+ return err;
+ }
+
+ for (i = 0; i < (1<<order); i++) {
+#ifdef CONFIG_X86_64
+ xen_l1_entry_update(pfn_array[i],
+ (__pa(vstart)>>PAGE_SHIFT)+i);
+#else
+ BUG_ON(HYPERVISOR_update_va_mapping(vstart + (i*PAGE_SIZE),
+ __pte_ma((pfn_array[i]<<PAGE_SHIFT)|__PAGE_KERNEL), 0));
+#endif
+ xen_machphys_update(pfn_array[i],
+ (__pa(vstart)>>PAGE_SHIFT)+i);
+ phys_to_machine_mapping[(__pa(vstart)>>PAGE_SHIFT)+i] =
+ pfn_array[i];
+ }
+
+ flush_tlb_all();
+
+ vfree(pfn_array);
+
+ free_pages(vstart, order);
+
+ return 0;
+}
+
EXPORT_SYMBOL(allocate_empty_lowmem_region);
+EXPORT_SYMBOL(unallocate_empty_lowmem_region);
/*
* Local variables:
diff -r 7c05931c1d0b -r a05f92511a99 linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c
--- a/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c Thu Aug 18 13:26:50 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c Mon Aug 22 09:50:48 2005
@@ -467,5 +467,23 @@
schedule_work(&balloon_worker);
}
+int balloon_get_pages(unsigned long *mfn_list, unsigned long nr_mfns)
+{
+ unsigned long flags;
+
+ balloon_lock(flags);
+ if ( HYPERVISOR_dom_mem_op(MEMOP_increase_reservation,
+ mfn_list, nr_mfns, 0) != nr_mfns ) {
+ WPRINTK("Unable to get memory pages from Balloon Driver");
+ balloon_unlock(flags);
+ return -ENOMEM;
+ }
+ current_pages += nr_mfns; /* non-atomic update */
+ balloon_unlock(flags);
+
+ schedule_work(&balloon_worker);
+}
+
EXPORT_SYMBOL(balloon_update_driver_allowance);
EXPORT_SYMBOL(balloon_put_pages);
+EXPORT_SYMBOL(balloon_get_pages);
diff -r 7c05931c1d0b -r a05f92511a99 linux-2.6-xen-sparse/include/asm-xen/balloon.h
--- a/linux-2.6-xen-sparse/include/asm-xen/balloon.h Thu Aug 18 13:26:50 2005
+++ b/linux-2.6-xen-sparse/include/asm-xen/balloon.h Mon Aug 22 09:50:48 2005
@@ -40,6 +40,9 @@
/* Give up unmapped pages to the balloon driver. */
extern void balloon_put_pages(unsigned long *mfn_list, unsigned long nr_mfns);
+/* Get an unmapped pages from the balloon driver. */
+extern int balloon_get_pages(unsigned long *mfn_list, unsigned long nr_mfns);
+
/*
* Prevent the balloon driver from changing the memory reservation during
* a driver critical region.
diff -r 7c05931c1d0b -r a05f92511a99 linux-2.6-xen-sparse/include/asm-xen/hypervisor.h
--- a/linux-2.6-xen-sparse/include/asm-xen/hypervisor.h Thu Aug 18 13:26:50 2005
+++ b/linux-2.6-xen-sparse/include/asm-xen/hypervisor.h Mon Aug 22 09:50:48 2005
@@ -142,6 +142,9 @@
/* Allocate a contiguous empty region of low memory. Return virtual start. */
unsigned long allocate_empty_lowmem_region(unsigned long pages);
+/* Unallocate a contiguous empty region of low memory which was previously
+ * allocated by allocate_empty_lowmem_region */
+int unallocate_empty_lowmem_region(unsigned long vstart, unsigned long pages);
#include <asm/hypercall.h>
#if defined(CONFIG_X86_64)
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