[3.16.y-ckt stable] Patch "efi: Disable interrupts around EFI calls, not in the epilog/prolog calls" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    efi: Disable interrupts around EFI calls, not in the epilog/prolog calls

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt23.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

---8<------------------------------------------------------------

>From 3fc550e9e44b3b82adf983f0a40f1be288230439 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo at kernel.org>
Date: Tue, 3 Mar 2015 07:34:33 +0100
Subject: efi: Disable interrupts around EFI calls, not in the epilog/prolog
 calls

commit 23a0d4e8fa6d3a1d7fb819f79bcc0a3739c30ba9 upstream.

Tapasweni Pathak reported that we do a kmalloc() in efi_call_phys_prolog()
on x86-64 while having interrupts disabled, which is a big no-no, as
kmalloc() can sleep.

Solve this by removing the irq disabling from the prolog/epilog calls
around EFI calls: it's unnecessary, as in this stage we are single
threaded in the boot thread, and we don't ever execute this from
interrupt contexts.

Reported-by: Tapasweni Pathak <tapaswenipathak at gmail.com>
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Matt Fleming <matt.fleming at intel.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/platform/efi/efi.c    |  7 +++++++
 arch/x86/platform/efi/efi_32.c | 11 +++--------
 arch/x86/platform/efi/efi_64.c |  3 ---
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 5bbb477f5c2a..09c8ac286cd5 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -236,12 +236,19 @@ static efi_status_t __init phys_efi_set_virtual_address_map(
 	efi_memory_desc_t *virtual_map)
 {
 	efi_status_t status;
+	unsigned long flags;

 	efi_call_phys_prelog();
+
+	/* Disable interrupts around EFI calls: */
+	local_irq_save(flags);
 	status = efi_call_phys(efi_phys.set_virtual_address_map,
 			       memory_map_size, descriptor_size,
 			       descriptor_version, virtual_map);
+	local_irq_restore(flags);
+
 	efi_call_phys_epilog();
+
 	return status;
 }

diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 9ee3491e31fb..be4e7eb41674 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -33,11 +33,10 @@

 /*
  * To make EFI call EFI runtime service in physical addressing mode we need
- * prelog/epilog before/after the invocation to disable interrupt, to
- * claim EFI runtime service handler exclusively and to duplicate a memory in
- * low memory space say 0 - 3G.
+ * prolog/epilog before/after the invocation to claim the EFI runtime service
+ * handler exclusively and to duplicate a memory mapping in low memory space,
+ * say 0 - 3G.
  */
-static unsigned long efi_rt_eflags;

 void efi_sync_low_kernel_mappings(void) {}
 void __init efi_dump_pagetable(void) {}
@@ -59,8 +58,6 @@ void efi_call_phys_prelog(void)
 {
 	struct desc_ptr gdt_descr;

-	local_irq_save(efi_rt_eflags);
-
 	load_cr3(initial_page_table);
 	__flush_tlb_all();

@@ -79,8 +76,6 @@ void efi_call_phys_epilog(void)

 	load_cr3(swapper_pg_dir);
 	__flush_tlb_all();
-
-	local_irq_restore(efi_rt_eflags);
 }

 void __init efi_runtime_mkexec(void)
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 290d397e1dd9..8139b4858403 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -42,7 +42,6 @@
 #include <asm/time.h>

 static pgd_t *save_pgd __initdata;
-static unsigned long efi_flags __initdata;

 /*
  * We allocate runtime services regions bottom-up, starting from -4G, i.e.
@@ -89,7 +88,6 @@ void __init efi_call_phys_prelog(void)
 		return;

 	early_code_mapping_set_exec(1);
-	local_irq_save(efi_flags);

 	n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
 	save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL);
@@ -117,7 +115,6 @@ void __init efi_call_phys_epilog(void)
 		set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]);
 	kfree(save_pgd);
 	__flush_tlb_all();
-	local_irq_restore(efi_flags);
 	early_code_mapping_set_exec(0);
 }