On 04/16/2013 04:09 AM, Matthew Garrett wrote:
EFI implementations distinguish between space that is actively used by a
variable and space that merely hasn't been garbage collected yet. Space
that hasn't yet been garbage collected isn't available for use and so isn't
counted in the remaining_space field returned by QueryVariableInfo().
Combined with commit 68d9298 this can cause problems. Some implementations
don't garbage collect until the remaining space is smaller than the maximum
variable size, and as a result check_var_size() will always fail once more
than 50% of the variable store has been used even if most of that space is
marked as available for garbage collection. The user is unable to create
new variables, and deleting variables doesn't increase the remaining space.
The problem that 68d9298 was attempting to avoid was one where certain
platforms fail if the actively used space is greater than 50% of the
available storage space. We should be able to calculate that by simply
summing the size of each available variable and subtracting that from
the total storage space. With luck this will fix the problem described in
https://bugzilla.kernel.org/show_bug.cgi?id=55471 without permitting
damage to occur to the machines 68d9298 was attempting to fix.
Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
---
arch/x86/platform/efi/efi.c | 109 +++++++++++++++++++++++++++++++++++++++++---
1 file changed, 102 insertions(+), 7 deletions(-)
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index e844d82..a3f03cd 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -41,6 +41,7 @@
#include <linux/io.h>
#include <linux/reboot.h>
#include <linux/bcd.h>
+#include <linux/ucs2_string.h>
#include <asm/setup.h>
#include <asm/efi.h>
@@ -51,6 +52,13 @@
#define EFI_DEBUG 1
+/*
+ * There's some additional metadata associated with each
+ * variable. Intel's reference implementation is 60 bytes - bump that
+ * to account for potential alignment constraints
+ */
+#define VAR_METADATA_SIZE 64
+
struct efi __read_mostly efi = {
.mps = EFI_INVALID_TABLE_ADDR,
.acpi = EFI_INVALID_TABLE_ADDR,
@@ -72,6 +80,9 @@ static efi_system_table_t efi_systab __initdata;
static u64 efi_var_store_size;
static u64 efi_var_remaining_size;
static u64 efi_var_max_var_size;
+static u64 boot_used_size;
+static u64 boot_var_size;
+static u64 active_size;
unsigned long x86_efi_facility;
@@ -166,8 +177,53 @@ static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
efi_char16_t *name,
efi_guid_t *vendor)
{
- return efi_call_virt3(get_next_variable,
- name_size, name, vendor);
+ efi_status_t status;
+ static bool finished = false;
+ static u64 var_size;
+
+ status = efi_call_virt3(get_next_variable,
+ name_size, name, vendor);
+
+ if (status == EFI_NOT_FOUND) {
+ finished = true;
+ if (var_size < boot_used_size) {
+ boot_var_size = boot_used_size - var_size;
+ active_size += boot_var_size;
Doesn't work sometimes. Here, if garbage is not collected, then
boot_used_size will contain the size of garbage, and get added into
active_size. This defeats the purpose of active_size.
I added a big printk before "return EFI_OUT_OF_RESOURCES", here are the
results (Dell XPS 8500, Secure Boot capable):
Failed to create variables in efivarfs, printk:
size=22
storage_size=131072
remaining_size=5230
max_size=5204
efi_var_store_size=131072
efi_var_remaining_size=5378
efi_var_max_var_size=5352
boot_used_size=125694
boot_var_size=125694
active_size=125694
After a few reboots,
EFI shell, QueryVariableInfo.efi:
MaximumVariableStorageSize=131072
RemainingVariableStorageSize=102113
MaximumVariableSize=65509
After several more pstore crash dumps, printk:
size=22
storage_size=131072
remaining_size=53064
max_size=53038
efi_var_store_size=131072
efi_var_remaining_size=53212
efi_var_max_var_size=53186
boot_used_size=77860
boot_var_size=77860
active_size=77860
After reboot, EFI shell, QueryVariableInfo.efi:
MaximumVariableStorageSize=131072
RemainingVariableStorageSize=50456
MaximumVariableSize=50430
-> reset ...
RemainingVariableStorageSize=47922
MaximumVariableSize=47896
-> reset ...
RemainingVariableStorageSize=45462
MaximumVariableSize=45436
-> reset ...
RemainingVariableStorageSize=43002
MaximumVariableSize=42976
-> reset ...
RemainingVariableStorageSize=40542
MaximumVariableSize=40516
Each reboot will consume some nvram? This is consistent with
http://article.gmane.org/gmane.linux.kernel.stable/47156
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