linux-kernel - [PATCH 3.14 015/130] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls

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Date:	Tue, 01 Mar 2016 23:51:01 +0000
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	<linux-kernel@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<stable@...r.kernel.org>,
	Tapasweni Pathak <tapaswenipathak@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt.fleming@...el.com>
Subject: [PATCH 3.14 015/130] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls

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

------------------

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

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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(-)

--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -248,12 +248,19 @@ static efi_status_t __init phys_efi_set_
 	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;
 }
 
--- 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)
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -41,7 +41,6 @@
 #include <asm/realmode.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.
@@ -87,7 +86,6 @@ 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);
@@ -115,7 +113,6 @@ 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);
 }