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Subject[PATCH V3 1/3] x86/efi: Call efi_delete_dummy_variable() after creating efi_rts_wq
Date
From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

Create a workqueue named efi_rts_wq (efi runtime services workqueue), so
that all efi_runtime_services() are executed in kthread context.

Invoking efi_runtime_services() through efi_rts_wq means all accesses to
efi_runtime_services() should be done after efi_rts_wq has been created.
efi_delete_dummy_variable() calls set_variable(), hence
efi_delete_dummy_variable() should be called after efi_rts_wq has been
created.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Suggested-by: Andy Lutomirski <luto@kernel.org>
Cc: Lee Chun-Yi <jlee@suse.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Naresh Bhat <naresh.bhat@linaro.org>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
---
arch/x86/platform/efi/efi.c | 15 +++++++++------
drivers/firmware/efi/arm-runtime.c | 3 +++
drivers/firmware/efi/efi.c | 25 +++++++++++++++++++++++++
include/linux/efi.h | 4 ++++
4 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 9061babfbc83..adcc55cd25ce 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -893,9 +893,6 @@ static void __init kexec_enter_virtual_mode(void)

if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
runtime_code_page_mkexec();
-
- /* clean DUMMY object */
- efi_delete_dummy_variable();
#endif
}

@@ -1015,9 +1012,6 @@ static void __init __efi_enter_virtual_mode(void)
* necessary relocation fixups for the new virtual addresses.
*/
efi_runtime_update_mappings();
-
- /* clean DUMMY object */
- efi_delete_dummy_variable();
}

void __init efi_enter_virtual_mode(void)
@@ -1031,6 +1025,15 @@ void __init efi_enter_virtual_mode(void)
__efi_enter_virtual_mode();

efi_dump_pagetable();
+
+ if (!efi_create_rts_wq())
+ return;
+
+ /*
+ * Clean DUMMY object calls EFI Runtime Service, set_variable(), so
+ * it should be invoked only after efi_rts_wq is ready.
+ */
+ efi_delete_dummy_variable();
}

static int __init arch_parse_efi_cmdline(char *str)
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 5889cbea60b8..6fb06130b53f 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -139,6 +139,9 @@ static int __init arm_enable_runtime_services(void)
return -ENOMEM;
}

+ if (!efi_create_rts_wq())
+ return 0;
+
/* Set up runtime services function pointers */
efi_native_runtime_setup();
set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 232f4915223b..b9103caa03b4 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -84,6 +84,8 @@ struct mm_struct efi_mm = {
.mmlist = LIST_HEAD_INIT(efi_mm.mmlist),
};

+struct workqueue_struct *efi_rts_wq;
+
static bool disable_runtime;
static int __init setup_noefi(char *arg)
{
@@ -337,6 +339,13 @@ static int __init efisubsys_init(void)
if (!efi_enabled(EFI_BOOT))
return 0;

+ /*
+ * If we failed to create efi_rts_wq, EFI_RUNTIME_SERVICES would
+ * have been be cleared, check for that condition.
+ */
+ if (!efi_enabled(EFI_RUNTIME_SERVICES))
+ return 0;
+
/* We register the efi directory at /sys/firmware/efi */
efi_kobj = kobject_create_and_add("efi", firmware_kobj);
if (!efi_kobj) {
@@ -971,3 +980,19 @@ static int register_update_efi_random_seed(void)
}
late_initcall(register_update_efi_random_seed);
#endif
+
+bool __init efi_create_rts_wq(void)
+{
+ /*
+ * Since we process only one efi_runtime_service() at a time, an
+ * ordered workqueue (which creates only one execution context)
+ * should suffice all our needs.
+ */
+ efi_rts_wq = alloc_ordered_workqueue("efi_rts_wq", 0);
+ if (!efi_rts_wq) {
+ pr_err("Creating efi_rts_wq failed, EFI runtime services disabled.\n");
+ clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+ return false;
+ }
+ return true;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 3016d8c456bc..565955010b18 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -987,6 +987,7 @@ extern void efi_map_pal_code (void);
extern void efi_memmap_walk (efi_freemem_callback_t callback, void *arg);
extern void efi_gettimeofday (struct timespec64 *ts);
extern void efi_enter_virtual_mode (void); /* switch EFI to virtual mode, if possible */
+extern bool __init efi_create_rts_wq(void);
#ifdef CONFIG_X86
extern void efi_late_init(void);
extern void efi_free_boot_services(void);
@@ -1651,4 +1652,7 @@ struct linux_efi_tpm_eventlog {

extern int efi_tpm_eventlog_init(void);

+/* Workqueue to queue EFI Runtime Services */
+extern struct workqueue_struct *efi_rts_wq;
+
#endif /* _LINUX_EFI_H */
--
2.7.4
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