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authorDan Williams <dan.j.williams@intel.com>2019-11-06 17:43:11 -0800
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-11-07 15:44:08 +0100
commitb617c5266eedbef2ccbb90931bb9175faa4ae0bc (patch)
treecaffea09ec6ac6271f5c3818b1207212a0aa6884 /drivers/firmware
parent6950e31b35fdf4588cbbdec1813091bb02cf8871 (diff)
efi: Common enable/disable infrastructure for EFI soft reservation
UEFI 2.8 defines an EFI_MEMORY_SP attribute bit to augment the interpretation of the EFI Memory Types as "reserved for a specific purpose". The proposed Linux behavior for specific purpose memory is that it is reserved for direct-access (device-dax) by default and not available for any kernel usage, not even as an OOM fallback. Later, through udev scripts or another init mechanism, these device-dax claimed ranges can be reconfigured and hot-added to the available System-RAM with a unique node identifier. This device-dax management scheme implements "soft" in the "soft reserved" designation by allowing some or all of the reservation to be recovered as typical memory. This policy can be disabled at compile-time with CONFIG_EFI_SOFT_RESERVE=n, or runtime with efi=nosoftreserve. As for this patch, define the common helpers to determine if the EFI_MEMORY_SP attribute should be honored. The determination needs to be made early to prevent the kernel from being loaded into soft-reserved memory, or otherwise allowing early allocations to land there. Follow-on changes are needed per architecture to leverage these helpers in their respective mem-init paths. Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/firmware')
-rw-r--r--drivers/firmware/efi/Kconfig21
-rw-r--r--drivers/firmware/efi/efi.c8
-rw-r--r--drivers/firmware/efi/libstub/efi-stub-helper.c19
3 files changed, 48 insertions, 0 deletions
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index b248870a9806..bcc378c19ebe 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -75,6 +75,27 @@ config EFI_MAX_FAKE_MEM
Ranges can be set up to this value using comma-separated list.
The default value is 8.
+config EFI_SOFT_RESERVE
+ bool "Reserve EFI Specific Purpose Memory"
+ depends on EFI && EFI_STUB && ACPI_HMAT
+ default ACPI_HMAT
+ help
+ On systems that have mixed performance classes of memory EFI
+ may indicate specific purpose memory with an attribute (See
+ EFI_MEMORY_SP in UEFI 2.8). A memory range tagged with this
+ attribute may have unique performance characteristics compared
+ to the system's general purpose "System RAM" pool. On the
+ expectation that such memory has application specific usage,
+ and its base EFI memory type is "conventional" answer Y to
+ arrange for the kernel to reserve it as a "Soft Reserved"
+ resource, and set aside for direct-access (device-dax) by
+ default. The memory range can later be optionally assigned to
+ the page allocator by system administrator policy via the
+ device-dax kmem facility. Say N to have the kernel treat this
+ memory as "System RAM" by default.
+
+ If unsure, say Y.
+
config EFI_PARAMS_FROM_FDT
bool
help
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index f8f8e273d809..e1cb915b45c6 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -81,6 +81,11 @@ bool efi_runtime_disabled(void)
return disable_runtime;
}
+bool __pure __efi_soft_reserve_enabled(void)
+{
+ return !efi_enabled(EFI_MEM_NO_SOFT_RESERVE);
+}
+
static int __init parse_efi_cmdline(char *str)
{
if (!str) {
@@ -94,6 +99,9 @@ static int __init parse_efi_cmdline(char *str)
if (parse_option_str(str, "noruntime"))
disable_runtime = true;
+ if (parse_option_str(str, "nosoftreserve"))
+ set_bit(EFI_MEM_NO_SOFT_RESERVE, &efi.flags);
+
return 0;
}
early_param("efi", parse_efi_cmdline);
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 35dbc2791c97..e02579907f2e 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -32,6 +32,7 @@ static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;
static int __section(.data) __nokaslr;
static int __section(.data) __quiet;
static int __section(.data) __novamap;
+static bool __section(.data) efi_nosoftreserve;
int __pure nokaslr(void)
{
@@ -45,6 +46,10 @@ int __pure novamap(void)
{
return __novamap;
}
+bool __pure __efi_soft_reserve_enabled(void)
+{
+ return !efi_nosoftreserve;
+}
#define EFI_MMAP_NR_SLACK_SLOTS 8
@@ -211,6 +216,10 @@ again:
if (desc->type != EFI_CONVENTIONAL_MEMORY)
continue;
+ if (efi_soft_reserve_enabled() &&
+ (desc->attribute & EFI_MEMORY_SP))
+ continue;
+
if (desc->num_pages < nr_pages)
continue;
@@ -305,6 +314,10 @@ efi_status_t efi_low_alloc_above(efi_system_table_t *sys_table_arg,
if (desc->type != EFI_CONVENTIONAL_MEMORY)
continue;
+ if (efi_soft_reserve_enabled() &&
+ (desc->attribute & EFI_MEMORY_SP))
+ continue;
+
if (desc->num_pages < nr_pages)
continue;
@@ -484,6 +497,12 @@ efi_status_t efi_parse_options(char const *cmdline)
__novamap = 1;
}
+ if (IS_ENABLED(CONFIG_EFI_SOFT_RESERVE) &&
+ !strncmp(str, "nosoftreserve", 7)) {
+ str += strlen("nosoftreserve");
+ efi_nosoftreserve = 1;
+ }
+
/* Group words together, delimited by "," */
while (*str && *str != ' ' && *str != ',')
str++;