[xen staging] Revert "EFI: free unused boot mem in at least some cases"

[patchbot@xxxxxxx]

commit 414d22cc092eab4a5b90d2ce594495733b07c77a
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Sep 16 11:16:41 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Sep 16 11:16:41 2020 +0200

    Revert "EFI: free unused boot mem in at least some cases"
    
    This reverts commit a4cbe0f3b47656ea125922fd48d394731a0163fd,
    which breaks PV shim in a not yet analyzed way.
---
 xen/arch/x86/efi/stub.c   |  6 ------
 xen/arch/x86/setup.c      | 26 +++-----------------------
 xen/arch/x86/tboot.c      | 12 ------------
 xen/common/efi/ebmalloc.c | 31 +++++--------------------------
 xen/include/xen/efi.h     |  1 -
 5 files changed, 8 insertions(+), 68 deletions(-)

diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.c
index 0e01e7322b..c578bffc71 100644
--- a/xen/arch/x86/efi/stub.c
+++ b/xen/arch/x86/efi/stub.c
@@ -52,12 +52,6 @@ bool efi_enabled(unsigned int feature)
 
 void __init efi_init_memory(void) { }
 
-bool efi_boot_mem_unused(unsigned long *start, unsigned long *end)
-{
-    *start = *end = (unsigned long)_end;
-    return false;
-}
-
 void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t l4e) { }
 
 bool efi_rs_using_pgtables(void)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 44c04e2735..4b15e067fa 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -830,7 +830,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     module_t *mod;
     unsigned long nr_pages, raw_max_page, modules_headroom, module_map[1];
     int i, j, e820_warn = 0, bytes = 0;
-    unsigned long eb_start, eb_end;
     bool acpi_boot_table_init_done = false, relocated = false;
     int ret;
     struct ns16550_defaults ns16550 = {
@@ -1146,8 +1145,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
         /*
          * This needs to remain in sync with xen_in_range() and the
-         * respective reserve_e820_ram() invocation below. No need to
-         * query efi_boot_mem_unused() here, though.
+         * respective reserve_e820_ram() invocation below.
          */
         mod[mbi->mods_count].mod_start = virt_to_mfn(_stext);
         mod[mbi->mods_count].mod_end = __2M_rwdata_end - _stext;
@@ -1419,18 +1417,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     if ( !xen_phys_start )
         panic("Not enough memory to relocate Xen\n");
 
-    /* FIXME: Putting a hole in .bss would shatter the large page mapping. */
-    if ( using_2M_mapping() )
-        efi_boot_mem_unused(NULL, NULL);
-
     /* This needs to remain in sync with xen_in_range(). */
-    if ( efi_boot_mem_unused(&eb_start, &eb_end) )
-    {
-        reserve_e820_ram(&boot_e820, __pa(_stext), __pa(eb_start));
-        reserve_e820_ram(&boot_e820, __pa(eb_end), __pa(__2M_rwdata_end));
-    }
-    else
-        reserve_e820_ram(&boot_e820, __pa(_stext), __pa(__2M_rwdata_end));
+    reserve_e820_ram(&boot_e820, __pa(_stext), __pa(__2M_rwdata_end));
 
     /* Late kexec reservation (dynamic start address). */
     kexec_reserve_area(&boot_e820);
@@ -1991,7 +1979,7 @@ int __hwdom_init xen_in_range(unsigned long mfn)
     paddr_t start, end;
     int i;
 
-    enum { region_s3, region_ro, region_rw, region_bss, nr_regions };
+    enum { region_s3, region_ro, region_rw, nr_regions };
     static struct {
         paddr_t s, e;
     } xen_regions[nr_regions] __hwdom_initdata;
@@ -2016,14 +2004,6 @@ int __hwdom_init xen_in_range(unsigned long mfn)
         /* hypervisor .data + .bss */
         xen_regions[region_rw].s = __pa(&__2M_rwdata_start);
         xen_regions[region_rw].e = __pa(&__2M_rwdata_end);
-        if ( efi_boot_mem_unused(&start, &end) )
-        {
-            ASSERT(__pa(start) >= xen_regions[region_rw].s);
-            ASSERT(__pa(end) <= xen_regions[region_rw].e);
-            xen_regions[region_rw].e = __pa(start);
-            xen_regions[region_bss].s = __pa(end);
-            xen_regions[region_bss].e = __pa(&__2M_rwdata_end);
-        }
     }
 
     start = (paddr_t)mfn << PAGE_SHIFT;
diff --git a/xen/arch/x86/tboot.c b/xen/arch/x86/tboot.c
index aadcce591f..e66b0940c4 100644
--- a/xen/arch/x86/tboot.c
+++ b/xen/arch/x86/tboot.c
@@ -1,4 +1,3 @@
-#include <xen/efi.h>
 #include <xen/init.h>
 #include <xen/types.h>
 #include <xen/lib.h>
@@ -365,8 +364,6 @@ void tboot_shutdown(uint32_t shutdown_type)
     /* if this is S3 then set regions to MAC */
     if ( shutdown_type == TB_SHUTDOWN_S3 )
     {
-        unsigned long s, e;
-
         /*
          * Xen regions for tboot to MAC. This needs to remain in sync with
          * xen_in_range().
@@ -381,15 +378,6 @@ void tboot_shutdown(uint32_t shutdown_type)
         /* hypervisor .data + .bss */
         g_tboot_shared->mac_regions[2].start = 
(uint64_t)__pa(&__2M_rwdata_start);
         g_tboot_shared->mac_regions[2].size = __2M_rwdata_end - 
__2M_rwdata_start;
-        if ( efi_boot_mem_unused(&s, &e) )
-        {
-            g_tboot_shared->mac_regions[2].size =
-                s - (unsigned long)__2M_rwdata_start;
-            g_tboot_shared->mac_regions[3].start = __pa(e);
-            g_tboot_shared->mac_regions[3].size =
-                (unsigned long)__2M_rwdata_end - e;
-            g_tboot_shared->num_mac_regions = 4;
-        }
 
         /*
          * MAC domains and other Xen memory
diff --git a/xen/common/efi/ebmalloc.c b/xen/common/efi/ebmalloc.c
index 136838eb8e..c65dbd946f 100644
--- a/xen/common/efi/ebmalloc.c
+++ b/xen/common/efi/ebmalloc.c
@@ -1,6 +1,5 @@
 #include "efi.h"
 #include <xen/init.h>
-#include <xen/mm.h>
 
 #ifdef CONFIG_ARM
 /*
@@ -22,7 +21,7 @@
 
 static char __section(".bss.page_aligned") __aligned(PAGE_SIZE)
     ebmalloc_mem[EBMALLOC_SIZE];
-static unsigned long __read_mostly ebmalloc_allocated;
+static unsigned long __initdata ebmalloc_allocated;
 
 /* EFI boot allocator. */
 void __init *ebmalloc(size_t size)
@@ -37,37 +36,17 @@ void __init *ebmalloc(size_t size)
     return ptr;
 }
 
-bool efi_boot_mem_unused(unsigned long *start, unsigned long *end)
-{
-    if ( !start && !end )
-    {
-        ebmalloc_allocated = sizeof(ebmalloc_mem);
-        return false;
-    }
-
-    *start = (unsigned long)ebmalloc_mem + PAGE_ALIGN(ebmalloc_allocated);
-    *end = (unsigned long)ebmalloc_mem + sizeof(ebmalloc_mem);
-
-    return *start < *end;
-}
-
 void __init free_ebmalloc_unused_mem(void)
 {
+#if 0 /* FIXME: Putting a hole in the BSS breaks the IOMMU mappings for dom0. 
*/
     unsigned long start, end;
 
-    if ( !efi_boot_mem_unused(&start, &end) )
-        return;
+    start = (unsigned long)ebmalloc_mem + PAGE_ALIGN(ebmalloc_allocated);
+    end = (unsigned long)ebmalloc_mem + sizeof(ebmalloc_mem);
 
     destroy_xen_mappings(start, end);
-
-#ifdef CONFIG_X86
-    /*
-     * By reserving the space early in the E820 map, it gets freed way before
-     * we make it here. Don't free the range a 2nd time.
-     */
-#else
     init_xenheap_pages(__pa(start), __pa(end));
-#endif
 
     printk(XENLOG_INFO "Freed %lukB unused BSS memory\n", (end - start) >> 10);
+#endif
 }
diff --git a/xen/include/xen/efi.h b/xen/include/xen/efi.h
index 94a7e547f9..44b7d3ec3a 100644
--- a/xen/include/xen/efi.h
+++ b/xen/include/xen/efi.h
@@ -33,7 +33,6 @@ struct compat_pf_efi_runtime_call;
 
 bool efi_enabled(unsigned int feature);
 void efi_init_memory(void);
-bool efi_boot_mem_unused(unsigned long *start, unsigned long *end);
 bool efi_rs_using_pgtables(void);
 unsigned long efi_get_time(void);
 void efi_halt_system(void);
--
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