From: Ard Biesheuvel ardb@kernel.org

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 --- drivers/firmware/efi/efi.c | 6 ++++-- drivers/firmware/efi/libstub/randomalloc.c | 3 +++ drivers/firmware/efi/libstub/relocate.c | 3 +++ include/linux/efi.h | 1 + 4 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 8296bf985d1d..7309394b8fc9 100644 --- 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 e5872e38d9a4..5a732018be36 100644 --- 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 99b45d1cd624..d4264bfb6dc1 100644 --- 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 053c57e61869..db293d7de686 100644 --- 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