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Preset lpj values when on VMware.

PATCH In review Alok Kataria 1 participant 2 messages Aug 2, 2010 – Aug 3, 2010

Subsystems (2)
x86 VMware hypervisor interface
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Alok Kataria

author
#0 lore raw

PATCH 1/1 Preset lpj values when on VMware.

Please consider the patch below for the tip tree. Thanks !

--
When running on VMware's platform, we have seen situations where the AP's try to calibrate the lpj values and fail to get good calibration runs becasue of timing issues. As a result delays don't work correctly on all cpus.
The solutions is to set preset_lpj value based on the current tsc frequency value. This is similar to what KVM does as well.

Signed-off-by Alok N Kataria <[email protected]>
arch/x86/kernel/cpu/vmware.c +8 -1
Index: linux-x86-tree.git/arch/x86/kernel/cpu/vmware.c
===================================================================
@@ -51,7 +51,7 @@ static inline int __vmware_platform(void
 
 static unsigned long vmware_get_tsc_khz(void)
 {
-	uint64_t tsc_hz;
+	uint64_t tsc_hz, lpj;
 	uint32_t eax, ebx, ecx, edx;
 
 	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);

@@ -62,6 +62,13 @@ static unsigned long vmware_get_tsc_khz(
 	printk(KERN_INFO "TSC freq read from hypervisor : %lu.%03lu MHz\n",
 			 (unsigned long) tsc_hz / 1000,
 			 (unsigned long) tsc_hz % 1000);
+
+	if (!preset_lpj) {
+		lpj = ((u64)tsc_hz * 1000);
+		do_div(lpj, HZ);
+		preset_lpj = lpj;
+	}
+
 	return tsc_hz;
 }
author
#1 lore raw

[tip:x86/vmware] x86, vmware: Preset lpj values when on VMware.

Commit-ID:  9f242dc10e0c3c1eb32d8c83c18650a35fd7f80d
Gitweb:     http://git.kernel.org/tip/9f242dc10e0c3c1eb32d8c83c18650a35fd7f80d
Author:     Alok Kataria <[email protected]>
AuthorDate: Mon, 2 Aug 2010 16:10:37 -0700
Committer:  H. Peter Anvin <[email protected]>
CommitDate: Mon, 2 Aug 2010 17:16:30 -0700

x86, vmware: Preset lpj values when on VMware.

When running on VMware's platform, we have seen situations where the AP's try to calibrate the lpj values and fail to get good calibration runs becasue of timing issues. As a result delays don't work correctly on all cpus.

The solutions is to set preset_lpj value based on the current tsc frequency value. This is similar to what KVM does as well.

Signed-off-by Alok N Kataria <[email protected]>

LKML-Reference: <[email protected]>

Signed-off-by H. Peter Anvin <[email protected]>
---
 arch/x86/kernel/cpu/vmware.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
arch/x86/kernel/cpu/vmware.c +8 -1
index b9d1ff5..227b044 100644
@@ -51,7 +51,7 @@ static inline int __vmware_platform(void)
 
 static unsigned long vmware_get_tsc_khz(void)
 {
-	uint64_t tsc_hz;
+	uint64_t tsc_hz, lpj;
 	uint32_t eax, ebx, ecx, edx;
 
 	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);

@@ -62,6 +62,13 @@ static unsigned long vmware_get_tsc_khz(void)
 	printk(KERN_INFO "TSC freq read from hypervisor : %lu.%03lu MHz\n",
 			 (unsigned long) tsc_hz / 1000,
 			 (unsigned long) tsc_hz % 1000);
+
+	if (!preset_lpj) {
+		lpj = ((u64)tsc_hz * 1000);
+		do_div(lpj, HZ);
+		preset_lpj = lpj;
+	}
+
 	return tsc_hz;
 }