x86/setup: Consolidate early memory reservations

The early reservations of memory areas used by the firmware, bootloader,
kernel text and data are spread over setup_arch(). Moreover, some of them
happen *after* memblock allocations, e.g trim_platform_memory_ranges() and
trim_low_memory_range() are called after reserve_real_mode() that allocates
memory.

There was no corruption of these memory regions because memblock always
allocates memory either from the end of memory (in top-down mode) or above
the kernel image (in bottom-up mode). However, the bottom up mode is going
to be updated to span the entire memory [1] to avoid limitations caused by
KASLR.

Consolidate early memory reservations in a dedicated function to improve
robustness against future changes. Having the early reservations in one
place also makes it clearer what memory must be reserved before memblock
allocations are allowed.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Baoquan He <bhe@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Link: [1] https://lore.kernel.org/lkml/20201217201214.3414100-2-guro@fb.com
Link: https://lkml.kernel.org/r/20210302100406.22059-2-rppt@kernel.org

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index d883176ef2ce04c1f86465b433d4a3b8ec74549e..3e3c6036b023251f654084f38a30e704eb49f916 100644 (file)
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -645,18 +645,6 @@ static void __init trim_snb_memory(void)
        }
 }
 
-/*
- * Here we put platform-specific memory range workarounds, i.e.
- * memory known to be corrupt or otherwise in need to be reserved on
- * specific platforms.
- *
- * If this gets used more widely it could use a real dispatch mechanism.
- */
-static void __init trim_platform_memory_ranges(void)
-{
-       trim_snb_memory();
-}
-
 static void __init trim_bios_range(void)
 {
        /*
@@ -729,7 +717,38 @@ static void __init trim_low_memory_range(void)
 {
        memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));
 }
-       
+
+static void __init early_reserve_memory(void)
+{
+       /*
+        * Reserve the memory occupied by the kernel between _text and
+        * __end_of_kernel_reserve symbols. Any kernel sections after the
+        * __end_of_kernel_reserve symbol must be explicitly reserved with a
+        * separate memblock_reserve() or they will be discarded.
+        */
+       memblock_reserve(__pa_symbol(_text),
+                        (unsigned long)__end_of_kernel_reserve - (unsigned long)_text);
+
+       /*
+        * Make sure page 0 is always reserved because on systems with
+        * L1TF its contents can be leaked to user processes.
+        */
+       memblock_reserve(0, PAGE_SIZE);
+
+       early_reserve_initrd();
+
+       if (efi_enabled(EFI_BOOT))
+               efi_memblock_x86_reserve_range();
+
+       memblock_x86_reserve_range_setup_data();
+
+       reserve_ibft_region();
+       reserve_bios_regions();
+
+       trim_snb_memory();
+       trim_low_memory_range();
+}
+
 /*
  * Dump out kernel offset information on panic.
  */
@@ -764,29 +783,6 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
 
 void __init setup_arch(char **cmdline_p)
 {
-       /*
-        * Reserve the memory occupied by the kernel between _text and
-        * __end_of_kernel_reserve symbols. Any kernel sections after the
-        * __end_of_kernel_reserve symbol must be explicitly reserved with a
-        * separate memblock_reserve() or they will be discarded.
-        */
-       memblock_reserve(__pa_symbol(_text),
-                        (unsigned long)__end_of_kernel_reserve - (unsigned long)_text);
-
-       /*
-        * Make sure page 0 is always reserved because on systems with
-        * L1TF its contents can be leaked to user processes.
-        */
-       memblock_reserve(0, PAGE_SIZE);
-
-       early_reserve_initrd();
-
-       /*
-        * At this point everything still needed from the boot loader
-        * or BIOS or kernel text should be early reserved or marked not
-        * RAM in e820. All other memory is free game.
-        */
-
 #ifdef CONFIG_X86_32
        memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
 
@@ -910,8 +906,18 @@ void __init setup_arch(char **cmdline_p)
 
        parse_early_param();
 
-       if (efi_enabled(EFI_BOOT))
-               efi_memblock_x86_reserve_range();
+       /*
+        * Do some memory reservations *before* memory is added to
+        * memblock, so memblock allocations won't overwrite it.
+        * Do it after early param, so we could get (unlikely) panic from
+        * serial.
+        *
+        * After this point everything still needed from the boot loader or
+        * firmware or kernel text should be early reserved or marked not
+        * RAM in e820. All other memory is free game.
+        */
+       early_reserve_memory();
+
 #ifdef CONFIG_MEMORY_HOTPLUG
        /*
         * Memory used by the kernel cannot be hot-removed because Linux
@@ -938,9 +944,6 @@ void __init setup_arch(char **cmdline_p)
 
        x86_report_nx();
 
-       /* after early param, so could get panic from serial */
-       memblock_x86_reserve_range_setup_data();
-
        if (acpi_mps_check()) {
 #ifdef CONFIG_X86_LOCAL_APIC
                disable_apic = 1;
@@ -1032,8 +1035,6 @@ void __init setup_arch(char **cmdline_p)
         */
        find_smp_config();
 
-       reserve_ibft_region();
-
        early_alloc_pgt_buf();
 
        /*
@@ -1054,8 +1055,6 @@ void __init setup_arch(char **cmdline_p)
         */
        sev_setup_arch();
 
-       reserve_bios_regions();
-
        efi_fake_memmap();
        efi_find_mirror();
        efi_esrt_init();
@@ -1081,9 +1080,6 @@ void __init setup_arch(char **cmdline_p)
 
        reserve_real_mode();
 
-       trim_platform_memory_ranges();
-       trim_low_memory_range();
-
        init_mem_mapping();
 
        idt_setup_early_pf();