efi: Avoid cold plugged memory for placing the kernel

commit ba69e0750b0362870294adab09339a0c39c3beaf upstream.

UEFI 2.11 introduced EFI_MEMORY_HOT_PLUGGABLE to annotate system memory
regions that are 'cold plugged' at boot, i.e., hot pluggable memory that
is available from early boot, and described as system RAM by the
firmware.

Existing loaders and EFI applications running in the boot context will
happily use this memory for allocating data structures that cannot be
freed or moved at runtime, and this prevents the memory from being
unplugged. Going forward, the new EFI_MEMORY_HOT_PLUGGABLE attribute
should be tested, and memory annotated as such should be avoided for
such allocations.

In the EFI stub, there are a couple of occurrences where, instead of the
high-level AllocatePages() UEFI boot service, a low-level code sequence
is used that traverses the EFI memory map and carves out the requested
number of pages from a free region. This is needed, e.g., for allocating
as low as possible, or for allocating pages at random.

While AllocatePages() should presumably avoid special purpose memory and
cold plugged regions, this manual approach needs to incorporate this
logic itself, in order to prevent the kernel itself from ending up in a
hot unpluggable region, preventing it from being unplugged.

So add the EFI_MEMORY_HOTPLUGGABLE macro definition, and check for it
where appropriate.

Cc: stable@vger.kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 28d4defc5d0cd23bd9059ad2ec22fc269c5b06f1..9786dfff9f840f97ea079edab75cbff16b1a0084 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -835,13 +835,15 @@ char * __init efi_md_typeattr_format(char *buf, size_t size,
                     EFI_MEMORY_WB | EFI_MEMORY_UCE | EFI_MEMORY_RO |
                     EFI_MEMORY_WP | EFI_MEMORY_RP | EFI_MEMORY_XP |
                     EFI_MEMORY_NV | EFI_MEMORY_SP | EFI_MEMORY_CPU_CRYPTO |
-                    EFI_MEMORY_RUNTIME | EFI_MEMORY_MORE_RELIABLE))
+                    EFI_MEMORY_MORE_RELIABLE | EFI_MEMORY_HOT_PLUGGABLE |
+                    EFI_MEMORY_RUNTIME))
                snprintf(pos, size, "|attr=0x%016llx]",
                         (unsigned long long)attr);
        else
                snprintf(pos, size,
-                        "|%3s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]",
+                        "|%3s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]",
                         attr & EFI_MEMORY_RUNTIME              ? "RUN" : "",
+                        attr & EFI_MEMORY_HOT_PLUGGABLE        ? "HP"  : "",
                         attr & EFI_MEMORY_MORE_RELIABLE        ? "MR"  : "",
                         attr & EFI_MEMORY_CPU_CRYPTO           ? "CC"  : "",
                         attr & EFI_MEMORY_SP                   ? "SP"  : "",

diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
index fff826f56728ccd85628dac969f85a3d1fd4ff93..5d88a5a46b09410176bbe2de8b7f7219cb7fc130 100644 (file)
--- a/drivers/firmware/efi/libstub/randomalloc.c
+++ b/drivers/firmware/efi/libstub/randomalloc.c
@@ -25,6 +25,9 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
        if (md->type != EFI_CONVENTIONAL_MEMORY)
                return 0;
 
+       if (md->attribute & EFI_MEMORY_HOT_PLUGGABLE)
+               return 0;
+
        if (efi_soft_reserve_enabled() &&
            (md->attribute & EFI_MEMORY_SP))
                return 0;

diff --git a/drivers/firmware/efi/libstub/relocate.c b/drivers/firmware/efi/libstub/relocate.c
index bf6fbd5d22a1a53af196be2a15f5593468f78da4..713ee2de02cf3f4edbf9aecaf1f78741a8fcbc81 100644 (file)
--- a/drivers/firmware/efi/libstub/relocate.c
+++ b/drivers/firmware/efi/libstub/relocate.c
@@ -53,6 +53,9 @@ efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
                if (desc->type != EFI_CONVENTIONAL_MEMORY)
                        continue;
 
+               if (desc->attribute & EFI_MEMORY_HOT_PLUGGABLE)
+                       continue;
+
                if (efi_soft_reserve_enabled() &&
                    (desc->attribute & EFI_MEMORY_SP))
                        continue;

diff --git a/include/linux/efi.h b/include/linux/efi.h
index a849b533be5b176656198648d1f55a6aaf37b1c0..1d73c77051c09b57b24d7ae38246e26fb567ba33 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -125,6 +125,7 @@ typedef     struct {
 #define EFI_MEMORY_RO          ((u64)0x0000000000020000ULL)    /* read-only */
 #define EFI_MEMORY_SP          ((u64)0x0000000000040000ULL)    /* soft reserved */
 #define EFI_MEMORY_CPU_CRYPTO  ((u64)0x0000000000080000ULL)    /* supports encryption */
+#define EFI_MEMORY_HOT_PLUGGABLE       BIT_ULL(20)     /* supports unplugging at runtime */
 #define EFI_MEMORY_RUNTIME     ((u64)0x8000000000000000ULL)    /* range requires runtime mapping */
 #define EFI_MEMORY_DESCRIPTOR_VERSION  1