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-rw-r--r--drivers/firmware/efi/runtime-wrappers.c19
-rw-r--r--drivers/firmware/efi/vars.c47
2 files changed, 66 insertions, 0 deletions
diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index 9694cba665c4..4349206198b2 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -200,6 +200,24 @@ static efi_status_t virt_efi_set_variable(efi_char16_t *name,
return status;
}
+static efi_status_t
+virt_efi_set_variable_nonblocking(efi_char16_t *name, efi_guid_t *vendor,
+ u32 attr, unsigned long data_size,
+ void *data)
+{
+ unsigned long flags;
+ efi_status_t status;
+
+ if (!spin_trylock_irqsave(&efi_runtime_lock, flags))
+ return EFI_NOT_READY;
+
+ status = efi_call_virt(set_variable, name, vendor, attr, data_size,
+ data);
+ spin_unlock_irqrestore(&efi_runtime_lock, flags);
+ return status;
+}
+
+
static efi_status_t virt_efi_query_variable_info(u32 attr,
u64 *storage_space,
u64 *remaining_space,
@@ -287,6 +305,7 @@ void efi_native_runtime_setup(void)
efi.get_variable = virt_efi_get_variable;
efi.get_next_variable = virt_efi_get_next_variable;
efi.set_variable = virt_efi_set_variable;
+ efi.set_variable_nonblocking = virt_efi_set_variable_nonblocking;
efi.get_next_high_mono_count = virt_efi_get_next_high_mono_count;
efi.reset_system = virt_efi_reset_system;
efi.query_variable_info = virt_efi_query_variable_info;
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 1fa724f31b0e..fa3c66bdc1e5 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -595,6 +595,39 @@ int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
}
EXPORT_SYMBOL_GPL(efivar_entry_set);
+/*
+ * efivar_entry_set_nonblocking - call set_variable_nonblocking()
+ *
+ * This function is guaranteed to not block and is suitable for calling
+ * from crash/panic handlers.
+ *
+ * Crucially, this function will not block if it cannot acquire
+ * __efivars->lock. Instead, it returns -EBUSY.
+ */
+static int
+efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
+ u32 attributes, unsigned long size, void *data)
+{
+ const struct efivar_operations *ops = __efivars->ops;
+ unsigned long flags;
+ efi_status_t status;
+
+ if (!spin_trylock_irqsave(&__efivars->lock, flags))
+ return -EBUSY;
+
+ status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
+ if (status != EFI_SUCCESS) {
+ spin_unlock_irqrestore(&__efivars->lock, flags);
+ return -ENOSPC;
+ }
+
+ status = ops->set_variable_nonblocking(name, &vendor, attributes,
+ size, data);
+
+ spin_unlock_irqrestore(&__efivars->lock, flags);
+ return efi_status_to_err(status);
+}
+
/**
* efivar_entry_set_safe - call set_variable() if enough space in firmware
* @name: buffer containing the variable name
@@ -622,6 +655,20 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
if (!ops->query_variable_store)
return -ENOSYS;
+ /*
+ * If the EFI variable backend provides a non-blocking
+ * ->set_variable() operation and we're in a context where we
+ * cannot block, then we need to use it to avoid live-locks,
+ * since the implication is that the regular ->set_variable()
+ * will block.
+ *
+ * If no ->set_variable_nonblocking() is provided then
+ * ->set_variable() is assumed to be non-blocking.
+ */
+ if (!block && ops->set_variable_nonblocking)
+ return efivar_entry_set_nonblocking(name, vendor, attributes,
+ size, data);
+
if (!block) {
if (!spin_trylock_irqsave(&__efivars->lock, flags))
return -EBUSY;