[PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary_cpu

[PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary_cpu

[Cyrill Gorcunov]

We should check if we have ESR register before writting to it.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---

Please review!
it seems the same nit in do_boot_cpu - checking now.

Index: linux-2.6.git/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
+++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
@@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
 	 * Give the other CPU some time to accept the IPI.
 	 */
 	udelay(200);
-	maxlvt = lapic_get_maxlvt();
-	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
-		apic_write(APIC_ESR, 0);
-	accept_status = (apic_read(APIC_ESR) & 0xEF);
+	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
+		maxlvt = lapic_get_maxlvt();
+		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
+			apic_write(APIC_ESR, 0);
+		accept_status = (apic_read(APIC_ESR) & 0xEF);
+	}
 	pr_debug("NMI sent.\n");
 
 	if (send_status)

Re: [PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary_cpu

[Ingo Molnar]

* Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> We should check if we have ESR register before writting to it.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> ---
> 
> Please review!
> it seems the same nit in do_boot_cpu - checking now.
> 
> Index: linux-2.6.git/arch/x86/kernel/smpboot.c
> ===================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
> +++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
> @@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
>  	 * Give the other CPU some time to accept the IPI.
>  	 */
>  	udelay(200);
> -	maxlvt = lapic_get_maxlvt();
> -	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
> -		apic_write(APIC_ESR, 0);
> -	accept_status = (apic_read(APIC_ESR) & 0xEF);
> +	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
> +		maxlvt = lapic_get_maxlvt();
> +		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
> +			apic_write(APIC_ESR, 0);
> +		accept_status = (apic_read(APIC_ESR) & 0xEF);
> +	}
>  	pr_debug("NMI sent.\n");

hm, is there any non-integrated lapic that has more than 3 lvts? iirc 
lvts were introduced with the integrated lapic.

	Ingo

Re: [PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary_cpu

[Cyrill Gorcunov]

[Ingo Molnar - Mon, Sep 15, 2008 at 09:56:55AM +0200]
| 
| * Cyrill Gorcunov <gorcunov@gmail.com> wrote:
| 
| > We should check if we have ESR register before writting to it.
| > 
| > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
| > ---
| > 
| > Please review!
| > it seems the same nit in do_boot_cpu - checking now.
| > 
| > Index: linux-2.6.git/arch/x86/kernel/smpboot.c
| > ===================================================================
| > --- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
| > +++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
| > @@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
| >  	 * Give the other CPU some time to accept the IPI.
| >  	 */
| >  	udelay(200);
| > -	maxlvt = lapic_get_maxlvt();
| > -	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| > -		apic_write(APIC_ESR, 0);
| > -	accept_status = (apic_read(APIC_ESR) & 0xEF);
| > +	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
| > +		maxlvt = lapic_get_maxlvt();
| > +		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| > +			apic_write(APIC_ESR, 0);
| > +		accept_status = (apic_read(APIC_ESR) & 0xEF);
| > +	}
| >  	pr_debug("NMI sent.\n");
| 
| hm, is there any non-integrated lapic that has more than 3 lvts? iirc 
| lvts were introduced with the integrated lapic.
| 
| 	Ingo
| 

Yes Ingo, but don't forget the next line in former

	accept_status = (apic_read(APIC_ESR) & 0xEF);

so we're protected in writting but _not_ in reading - which
is buggy a bit :-)

		- Cyrill -

Re: [PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary_cpu

[Cyrill Gorcunov]

[Cyrill Gorcunov - Mon, Sep 15, 2008 at 02:01:19PM +0400]
| [Ingo Molnar - Mon, Sep 15, 2008 at 09:56:55AM +0200]
| | 
| | * Cyrill Gorcunov <gorcunov@gmail.com> wrote:
| | 
| | > We should check if we have ESR register before writting to it.
| | > 
| | > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
| | > ---
| | > 
| | > Please review!
| | > it seems the same nit in do_boot_cpu - checking now.
| | > 
| | > Index: linux-2.6.git/arch/x86/kernel/smpboot.c
| | > ===================================================================
| | > --- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
| | > +++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
| | > @@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
| | >  	 * Give the other CPU some time to accept the IPI.
| | >  	 */
| | >  	udelay(200);
| | > -	maxlvt = lapic_get_maxlvt();
| | > -	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| | > -		apic_write(APIC_ESR, 0);
| | > -	accept_status = (apic_read(APIC_ESR) & 0xEF);
| | > +	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
| | > +		maxlvt = lapic_get_maxlvt();
| | > +		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| | > +			apic_write(APIC_ESR, 0);
| | > +		accept_status = (apic_read(APIC_ESR) & 0xEF);
| | > +	}
| | >  	pr_debug("NMI sent.\n");
| | 
| | hm, is there any non-integrated lapic that has more than 3 lvts? iirc 
| | lvts were introduced with the integrated lapic.
| | 
| | 	Ingo
| | 
| 
| Yes Ingo, but don't forget the next line in former
| 
| 	accept_status = (apic_read(APIC_ESR) & 0xEF);
| 
| so we're protected in writting but _not_ in reading - which
| is buggy a bit :-)
|
| 		- Cyrill -

Ingo - could you replace in this patch message and subject -
writting to reading - it will be more correct.

		- Cyrill -

Re: [PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary_cpu

[Cyrill Gorcunov]

[Ingo Molnar - Mon, Sep 15, 2008 at 09:56:55AM +0200]
| 
| * Cyrill Gorcunov <gorcunov@gmail.com> wrote:
| 
| > We should check if we have ESR register before writting to it.
| > 
| > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
| > ---
| > 
| > Please review!
| > it seems the same nit in do_boot_cpu - checking now.
| > 
| > Index: linux-2.6.git/arch/x86/kernel/smpboot.c
| > ===================================================================
| > --- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
| > +++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
| > @@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
| >  	 * Give the other CPU some time to accept the IPI.
| >  	 */
| >  	udelay(200);
| > -	maxlvt = lapic_get_maxlvt();
| > -	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| > -		apic_write(APIC_ESR, 0);
| > -	accept_status = (apic_read(APIC_ESR) & 0xEF);
| > +	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
| > +		maxlvt = lapic_get_maxlvt();
| > +		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| > +			apic_write(APIC_ESR, 0);
| > +		accept_status = (apic_read(APIC_ESR) & 0xEF);
| > +	}
| >  	pr_debug("NMI sent.\n");
| 
| hm, is there any non-integrated lapic that has more than 3 lvts? iirc 
| lvts were introduced with the integrated lapic.
| 
| 	Ingo
| 

Ingo, here is an updated version of patch - only subject
and patch message updated (not patch body)

		- Cyrill -
---
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: x86: wakeup_secondary_cpu - check if we have ESR register to read

We shouldn't read ESR register on discrete APIC.
Check it first.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---

Index: linux-2.6.git/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
+++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
@@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
 	 * Give the other CPU some time to accept the IPI.
 	 */
 	udelay(200);
-	maxlvt = lapic_get_maxlvt();
-	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
-		apic_write(APIC_ESR, 0);
-	accept_status = (apic_read(APIC_ESR) & 0xEF);
+	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
+		maxlvt = lapic_get_maxlvt();
+		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
+			apic_write(APIC_ESR, 0);
+		accept_status = (apic_read(APIC_ESR) & 0xEF);
+	}
 	pr_debug("NMI sent.\n");
 
 	if (send_status)