Re: [Xen-devel] [PATCH V3 4/8] xen: Delay invalidating extra memory

[Juergen Gross]

On 11/12/2014 11:10 PM, Konrad Rzeszutek Wilk wrote:

@@ -376,12 +374,14 @@ void __init xen_build_dynamic_phys_to_machine(void)
        unsigned long max_pfn;
        unsigned long pfn;

-        if (xen_feature(XENFEAT_auto_translated_physmap))
+       if (xen_feature(XENFEAT_auto_translated_physmap))

Spurious change.

I'll remove it.

.. snip..

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 0e5f9b6..8d5985b 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -75,7 +75,6 @@ static unsigned long xen_remap_mfn __initdata = 
INVALID_P2M_ENTRY;

  static void __init xen_add_extra_mem(u64 start, u64 size)
  {
-       unsigned long pfn;
        int i;

        for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
@@ -95,17 +94,74 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
                printk(KERN_WARNING "Warning: not enough extra memory 
regions\n");

        memblock_reserve(start, size);
+}

-       xen_max_p2m_pfn = PFN_DOWN(start + size);
-       for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
-               unsigned long mfn = pfn_to_mfn(pfn);
+static void __init xen_del_extra_mem(u64 start, u64 size)
+{
+       int i;
+       u64 start_r, size_r;

-               if (WARN_ONCE(mfn == pfn, "Trying to over-write 1-1 mapping (pfn: 
%lx)\n", pfn))
-                       continue;
-               WARN_ONCE(mfn != INVALID_P2M_ENTRY, "Trying to remove %lx which has 
%lx mfn!\n",
-                         pfn, mfn);
+       for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+               start_r = xen_extra_mem[i].start;
+               size_r = xen_extra_mem[i].size;
+
+               /* Start of region. */
+               if (start_r == start) {
+                       BUG_ON(size > size_r);
+                       xen_extra_mem[i].start += size;
+                       xen_extra_mem[i].size -= size;
+                       break;
+               }
+               /* End of region. */
+               if (start_r + size_r == start + size) {
+                       BUG_ON(size > size_r);
+                       xen_extra_mem[i].size -= size;
+                       break;
+               }
+               /* Mid of region. */
+               if (start > start_r && start < start_r + size_r) {
+                       BUG_ON(start + size > start_r + size_r);
+                       xen_extra_mem[i].size = start - start_r;
+                       xen_add_extra_mem(start + size, start_r + size_r -
+                                         (start + size));

Which ends up calling 'memblock_reserve' for an region it already has
reserved. Should we call memblock_free(start_r, size_r - size) before calling 
this?

Or is that not neccessary as memblock_* is pretty smart about this sort of 
thing?

Regions marked via memblock_reserve() are allowed to overlap. I can add
a comment.


Juergen


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