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

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Message-ID: <4E972001.3080204@linux.vnet.ibm.com>
Date:	Thu, 13 Oct 2011 22:59:37 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Tejun Heo <tj@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"pavel@....cz" <pavel@....cz>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"suresh.b.siddha@...el.com" <suresh.b.siddha@...el.com>,
	"lucas.demarchi@...fusion.mobi" <lucas.demarchi@...fusion.mobi>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"rdunlap@...otime.net" <rdunlap@...otime.net>,
	"vatsa@...ux.vnet.ibm.com" <vatsa@...ux.vnet.ibm.com>,
	"ashok.raj@...el.com" <ashok.raj@...el.com>,
	"tigran@...azian.fsnet.co.uk" <tigran@...azian.fsnet.co.uk>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] Mutually exclude cpu online and suspend/hibernate

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

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