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SubjectRe: [patch 4/4] x86: apic_is_clustered_box to indicate unsynched TSC's on multiboard vSMP systems
On Sat, Mar 22, 2008 at 09:02:51PM +0100, Ingo Molnar wrote:
>
>* Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
>
>> OK. Something like this?
>
>yeah.
>
>small nit:
>
>> +int is_vsmp_box(void)
>> +{
>> + if (is_vsmp != -1)
>> + return is_vsmp;
>> + else {
>> + printk("ScaleMP vSMPowered system detection called too early!\n");
>> + return 0;
>> + }
>> }
>
>since this is an "impossible" scenario, just stick in a WARN_ON_ONCE().
>

Sure. Here's the modified patch.

vSMP detection: Access pci config space early in boot to detect if the
system is a vSMPowered box, and cache the result in a flag, so that
is_vsmp_box() retrieves the value of the flag always.

Signed-off-by; Ravikiran Thirumalai <kiran@scalex86.org>

Index: linux.git.trees/arch/x86/kernel/vsmp_64.c
===================================================================
--- linux.git.trees.orig/arch/x86/kernel/vsmp_64.c 2008-03-21 13:15:17.000000000 -0700
+++ linux.git.trees/arch/x86/kernel/vsmp_64.c 2008-03-24 13:57:09.387437626 -0700
@@ -108,25 +108,34 @@ static void __init set_vsmp_pv_ops(void)
#endif

#ifdef CONFIG_PCI
-static int vsmp = -1;
+static int is_vsmp = -1;

-int is_vsmp_box(void)
+static void __init detect_vsmp_box(void)
{
- if (vsmp != -1)
- return vsmp;
+ is_vsmp = 0;

- vsmp = 0;
if (!early_pci_allowed())
- return vsmp;
+ return;

- /* Check if we are running on a ScaleMP vSMP box */
+ /* Check if we are running on a ScaleMP vSMPowered box */
if (read_pci_config(0, 0x1f, 0, PCI_VENDOR_ID) ==
(PCI_VENDOR_ID_SCALEMP | (PCI_DEVICE_ID_SCALEMP_VSMP_CTL << 16)))
- vsmp = 1;
+ is_vsmp = 1;
+}

- return vsmp;
+int is_vsmp_box(void)
+{
+ if (is_vsmp != -1)
+ return is_vsmp;
+ else {
+ WARN_ON_ONCE(1);
+ return 0;
+ }
}
#else
+static int __init detect_vsmp_box(void)
+{
+}
int is_vsmp_box(void)
{
return 0;
@@ -135,6 +144,7 @@ int is_vsmp_box(void)

void __init vsmp_init(void)
{
+ detect_vsmp_box();
if (!is_vsmp_box())
return;


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