Re: [PATCH v2 2/3] Mutually exclude cpu online and suspend/hibernate

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

On 10/13/2011 10:31 PM, Borislav Petkov wrote:
> On Thu, Oct 13, 2011 at 12:06:02PM -0400, Tejun Heo wrote:
>> I hate to sound like a broken recorder but the above patch isn't
>> strictly correct for hot-swap cases, right?
> 
> hpa is working on a ucode loading solution which will take care of your
> hotswap case too.
> 

Tejun, I have written a patch below (untested) that does what you said.
So Boris, hpa's work would make such a patch unnecessary is it?

Thanks,
Srivatsa S. Bhat

---

 arch/x86/kernel/microcode_core.c |   33 +++++++++++++++++++++++++++++++++
 1 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index f924280..849ae2d 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -155,6 +155,27 @@ static int collect_cpu_info(int cpu)
 	return ret;
 }
 
+/*
+ * Compare the microcode revision that the kernel has in memory
+ * for this cpu and the microcode revision that we need to apply
+ * on this cpu. If they match, return 0, else return -1.
+ */
+static int compare_cpu_with_microcode(int cpu)
+{
+	struct ucode_cpu_info *uci_mem = ucode_cpu_info + cpu;
+	struct ucode_cpu_info uci_cpu;
+	int ret;
+
+	ret = collect_cpu_info_on_target(cpu, &uci_cpu->cpu_sig);
+	if(!ret) {
+		if (!(uci_mem->cpu_sig->sig == uci_cpu->cpu_sig->sig &&
+		      uci_mem->cpu_sig->pf == uci_cpu->cpu_sig->pf &&
+		      uci_mem->cpu_sig->rev == uci_cpu->cpu_sig->rev))
+			ret = -1;
+	}
+	return ret;
+}
+
 struct apply_microcode_ctx {
 	int err;
 };
@@ -397,6 +418,18 @@ static enum ucode_state microcode_update_cpu(int cpu)
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	enum ucode_state ustate;
 
+	/*
+	 * If the CPU on which we are going to update the
+	 * microcode and the microcode which we currently
+	 * have in kernel memory are incompatible, then
+	 * invalidate the microcode that we have (and also
+	 * free its memory), so that we can get the required
+	 * microcode afresh.
+	 */
+	if (compare_cpu_with_microcode(cpu)) {
+		microcode_fini_cpu(cpu);
+	}
+
 	if (uci->valid)
 		ustate = microcode_resume_cpu(cpu);
 	else