linux-kernel - [PATCH 3.12 01/39] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls

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Date:	Mon, 25 Jan 2016 12:49:42 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Luis Henriques <luis.henriques@...onical.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 01/39] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls

From: Ingo Molnar <mingo@...nel.org>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Matt Fleming <matt.fleming@...el.com>
[ luis: backported to 3.10: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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 f19284d87dfe..9167de031e47 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -250,12 +250,19 @@ 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_phys4(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 40e446941dd7..bebbee05e331 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -33,19 +33,16 @@
 
 /*
  * 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_call_phys_prelog(void)
 {
 	struct desc_ptr gdt_descr;
 
-	local_irq_save(efi_rt_eflags);
-
 	load_cr3(initial_page_table);
 	__flush_tlb_all();
 
@@ -64,6 +61,4 @@ void efi_call_phys_epilog(void)
 
 	load_cr3(swapper_pg_dir);
 	__flush_tlb_all();
-
-	local_irq_restore(efi_rt_eflags);
 }
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 39a0e7f1f0a3..2f6c1a9734c8 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -40,7 +40,6 @@
 #include <asm/fixmap.h>
 
 static pgd_t *save_pgd __initdata;
-static unsigned long efi_flags __initdata;
 
 static void __init early_code_mapping_set_exec(int executable)
 {
@@ -66,7 +65,6 @@ void __init efi_call_phys_prelog(void)
 	int n_pgds;
 
 	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);
@@ -90,7 +88,6 @@ 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);
 }
 
-- 
2.7.0