linux-kernel - [PATCH] x86, ucode-amd: Ensure ucode update on suspend/resume after CPU off/online cycle

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Date:	Wed, 11 Nov 2009 20:03:29 +0100
From:	Andreas Herrmann <herrmann.der.user@...glemail.com>
To:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, dimm <dmitry.adamushko@...il.com>
Subject: [PATCH] x86, ucode-amd: Ensure ucode update on suspend/resume
 after CPU off/online cycle

When switching a CPU offline/online and then doing suspend/resume,
ucode is not updated on this CPU.

This is due to the microcode_fini_cpu() call which frees uci->mc
when setting the CPU offline:

  static void microcode_fini_cpu_amd(int cpu)
  {
          struct ucode_cpu_info *uci = ucode_cpu_info + cpu;

          vfree(uci->mc);
          uci->mc = NULL;
  }

When the CPU is set online uci->mc is still NULL because no ucode
update is required.

Finally this prevents ucode update when resuming after suspend:

  static enum ucode_state microcode_resume_cpu(int cpu)
  {
        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;

        if (!uci->mc)
                return UCODE_NFOUND;

        ...
  }

Fix is to check whether uci->mc is valid before microcode_resume_cpu()
is called.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
---
 arch/x86/kernel/microcode_core.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index 230fb09..e68aae3 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -391,7 +391,7 @@ static enum ucode_state microcode_update_cpu(int cpu)
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	enum ucode_state ustate;
 
-	if (uci->valid)
+	if (uci->valid && uci->mc)
 		ustate = microcode_resume_cpu(cpu);
 	else
 		ustate = microcode_init_cpu(cpu);
-- 
1.6.5.2

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