efi: Avoid cold plugged memory for placing the kernel

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>

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 8296bf985d1d12778d904fde2a74705eae6e8b26..7309394b8fc98cf7a3424af209b752f0251c8c89 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -934,13 +934,15 @@ 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 e5872e38d9a46900c7c63050336b8bed08282763..5a732018be36dacbd61805acf49cfa37e7551764 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 99b45d1cd62462ea0e8ff8d94b982fd62afeb593..d4264bfb6dc1749f4c02e84f3551b5e13a240ca3 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 053c57e61869806723c25c459c6213b3eae2330a..db293d7de6864ed4853096e4563530fd8bd5e9c8 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -128,6 +128,7 @@ 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