[Xen-devel] [PATCH] x86: fix memory cut-off when using PFN compression

["Jan Beulich" <JBeulich@xxxxxxxx>]

For one setup_max_pdx(), when invoked a second time (after SRAT got
parsed), needs to start from the original max_page value again (using
the already adjusted one from the first invocation would not allow the
cut-off boundary to be moved up).

Second, _if_ we need to cut off some part of memory, we must not allow
this to also propagate into the NUMA accounting. Otherwise
cutoff_node() results in nodes_cover_memory() to find some parts of
memory apparently not having a PXM association, causing all SRAT info
to be ignored.

The only possibly problematic consumer of node_spanned_pages (the
meaning of which gets altered here in that it now also includes memory
Xen can't actively make use of) is XEN_SYSCTL_numainfo: At a first
glance the potentially larger reported memory size shouldn't confuse
tool stacks.

And finally we must not put our boot time modules at addresses which
(at that time) can't be guaranteed to be accessible later. This applies
to both the EFI boot loader and the module relocation code.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/efi/boot.c
+++ b/xen/arch/x86/efi/boot.c
@@ -459,7 +459,8 @@ static bool_t __init read_file(EFI_FILE_
         what = what ?: L"Seek";
     else
     {
-        file->addr = (EFI_PHYSICAL_ADDRESS)1 << (32 + PAGE_SHIFT);
+        file->addr = min(1UL << (32 + PAGE_SHIFT),
+                         HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START);
         ret = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
                                     PFN_UP(size), &file->addr);
     }
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -378,9 +378,9 @@ static uint64_t __init consider_modules(
     return e;
 }
 
-static void __init setup_max_pdx(void)
+static void __init setup_max_pdx(unsigned long top_page)
 {
-    max_pdx = pfn_to_pdx(max_page - 1) + 1;
+    max_pdx = pfn_to_pdx(top_page - 1) + 1;
 
     if ( max_pdx > (DIRECTMAP_SIZE >> PAGE_SHIFT) )
         max_pdx = DIRECTMAP_SIZE >> PAGE_SHIFT;
@@ -548,7 +548,7 @@ void __init __start_xen(unsigned long mb
     unsigned int initrdidx;
     multiboot_info_t *mbi = __va(mbi_p);
     module_t *mod = (module_t *)__va(mbi->mods_addr);
-    unsigned long nr_pages, modules_headroom, *module_map;
+    unsigned long nr_pages, raw_max_page, modules_headroom, *module_map;
     int i, j, e820_warn = 0, bytes = 0;
     bool_t acpi_boot_table_init_done = 0;
     struct ns16550_defaults ns16550 = {
@@ -752,7 +752,7 @@ void __init __start_xen(unsigned long mb
     }
 
     /* Sanitise the raw E820 map to produce a final clean version. */
-    max_page = init_e820(memmap_type, e820_raw, &e820_raw_nr);
+    max_page = raw_max_page = init_e820(memmap_type, e820_raw, &e820_raw_nr);
 
     /* Create a temporary copy of the E820 map. */
     memcpy(&boot_e820, &e820, sizeof(e820));
@@ -821,7 +821,10 @@ void __init __start_xen(unsigned long mb
                              (end - s) >> PAGE_SHIFT, PAGE_HYPERVISOR);
         }
 
-        e = min_t(uint64_t, e, 1ULL << (PAGE_SHIFT + 32));
+        if ( e > min(HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START,
+                     1UL << (PAGE_SHIFT + 32)) )
+            e = min(HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START,
+                    1UL << (PAGE_SHIFT + 32));
 #define reloc_size ((__pa(&_end) + mask) & ~mask)
         /* Is the region suitable for relocating Xen? */
         if ( !xen_phys_start && e <= limit )
@@ -970,7 +973,7 @@ void __init __start_xen(unsigned long mb
     /* Late kexec reservation (dynamic start address). */
     kexec_reserve_area(&boot_e820);
 
-    setup_max_pdx();
+    setup_max_pdx(raw_max_page);
     if ( highmem_start )
         xenheap_max_mfn(PFN_DOWN(highmem_start));
 
@@ -996,7 +999,7 @@ void __init __start_xen(unsigned long mb
         {
             acpi_boot_table_init_done = 1;
             srat_parse_regions(s);
-            setup_max_pdx();
+            setup_max_pdx(raw_max_page);
         }
 
         if ( pfn_to_pdx((e - 1) >> PAGE_SHIFT) >= max_pdx )
@@ -1134,7 +1137,7 @@ void __init __start_xen(unsigned long mb
 
     acpi_numa_init();
 
-    numa_initmem_init(0, max_page);
+    numa_initmem_init(0, raw_max_page);
 
     end_boot_allocator();
     system_state = SYS_STATE_boot;

Attachment: x86-memory-cut-off.patch
Description: Text document

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