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From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 01/16] x86/microcode/intel: Drop stashed AP patch pointer optimization
Date: Fri, 20 Jan 2017 21:29:40 +0100	[thread overview]
Message-ID: <20170120202955.4091-2-bp@alien8.de> (raw)
In-Reply-To: <20170120202955.4091-1-bp@alien8.de>

From: Borislav Petkov <bp@suse.de>

This was meant to save us the scanning of the microcode containter in
the initrd since the first AP had already done that but it can also hurt
us:

Imagine a single hyperthreaded CPU (Intel(R) Atom(TM) CPU N270, for
example) which updates the microcode on the BSP but since the microcode
engine is shared between the two threads, the update on CPU1 doesn't
happen because it has already happened on CPU0 and we don't find a newer
microcode revision on CPU1.

Which doesn't set the intel_ucode_patch pointer and at initrd
jettisoning time we don't save the microcode patch for later
application.

Now, when we suspend to RAM, the loaded microcode gets cleared so we
need to reload but there's no patch saved in the cache.

Removing the optimization fixes this issue and all is fine and dandy.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Fixes: 06b8534cb728 ("x86/microcode: Rework microcode loading")
---
 arch/x86/kernel/cpu/microcode/intel.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 3f329b74e040..8325d8a09ab0 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -41,7 +41,7 @@
 
 static const char ucode_path[] = "kernel/x86/microcode/GenuineIntel.bin";
 
-/* Current microcode patch used in early patching */
+/* Current microcode patch used in early patching on the APs. */
 struct microcode_intel *intel_ucode_patch;
 
 static inline bool cpu_signatures_match(unsigned int s1, unsigned int p1,
@@ -607,12 +607,6 @@ int __init save_microcode_in_initrd_intel(void)
 	struct ucode_cpu_info uci;
 	struct cpio_data cp;
 
-	/*
-	 * AP loading didn't find any microcode patch, no need to save anything.
-	 */
-	if (!intel_ucode_patch || IS_ERR(intel_ucode_patch))
-		return 0;
-
 	if (!load_builtin_intel_microcode(&cp))
 		cp = find_microcode_in_initrd(ucode_path, false);
 
@@ -628,7 +622,6 @@ int __init save_microcode_in_initrd_intel(void)
 	return 0;
 }
 
-
 /*
  * @res_patch, output: a pointer to the patch we found.
  */
-- 
2.11.0

  reply	other threads:[~2017-01-20 20:31 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-20 20:29 [PATCH 00/16 v2] x86/microcode: 4.11 queue Borislav Petkov
2017-01-20 20:29 ` Borislav Petkov [this message]
2017-01-23  9:07   ` [tip:x86/mce] x86/microcode/intel: Drop stashed AP patch pointer optimization tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 02/16] x86/MSR: Carve out bare minimum accessors Borislav Petkov
2017-01-23  9:07   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 03/16] x86/microcode: Convert to bare minimum MSR accessors Borislav Petkov
2017-01-23  9:08   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 04/16] x86/microcode/AMD: Clean up find_equiv_id() Borislav Petkov
2017-01-23  9:08   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 05/16] x86/microcode/AMD: Shorten function parameter's name Borislav Petkov
2017-01-23  9:09   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 06/16] x86/microcode/AMD: Extend the container struct Borislav Petkov
2017-01-23  9:09   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 07/16] x86/microcode/AMD: Rework container parsing Borislav Petkov
2017-01-23  9:10   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 08/16] x86/microcode: Decrease CPUID use Borislav Petkov
2017-01-23  9:10   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 09/16] x86/microcode/AMD: Get rid of global this_equiv_id Borislav Petkov
2017-01-23  9:11   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 10/16] x86/microcode/AMD: Use find_microcode_in_initrd() Borislav Petkov
2017-01-23  9:11   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 11/16] x86/microcode: Remove local vendor variable Borislav Petkov
2017-01-23  9:12   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 12/16] x86/microcode/AMD: Check patch level only on the BSP Borislav Petkov
2017-01-23  9:12   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 13/16] x86/microcode/AMD: Unify load_ucode_amd_ap() Borislav Petkov
2017-01-23  9:13   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 14/16] x86/microcode/AMD: Simplify saving from initrd Borislav Petkov
2017-01-23  9:13   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 15/16] x86/microcode/AMD: Remove AP scanning optimization Borislav Petkov
2017-01-23  9:14   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 16/16] x86/microcode/AMD: Remove struct cont_desc.eq_id Borislav Petkov
2017-01-23  9:14   ` [tip:x86/mce] " tip-bot for Borislav Petkov

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