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x86/vmware: Skip lapic calibration on VMware.

PATCH New Renat Valiullin 2 participants 2 messages Oct 4, 2016 – Oct 5, 2016

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x86 virtio core VMware hypervisor interface
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Renat Valiullin

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PATCH 1/1 x86/vmware: Skip lapic calibration on VMware.

In virtualized environment the APIC timer calibration could go wrong when the host is overcommitted or the guest is running nested, this would result in the APIC timers operating at an incorrect frequency. Since VMware supports a mechanism to retrieve the local APIC frequency we can ask the hypervisor for it and skip this APIC calibration loop.

Signed-off-by Renat Valiullin <[email protected]>
Acked-by Alok N Kataria <[email protected]>
---
 arch/x86/kernel/cpu/vmware.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
arch/x86/kernel/cpu/vmware.c +10 -2
index 1ff0598..8116057 100644
@@ -27,6 +27,7 @@
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
+#include <asm/apic.h>
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868

@@ -82,10 +83,17 @@ static void __init vmware_platform_setup(void)
 
 	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
 
-	if (ebx != UINT_MAX)
+	if (ebx != UINT_MAX) {
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
-	else
+#ifdef CONFIG_X86_LOCAL_APIC
+		/* Skip lapic calibration since we know the bus frequency. */
+		lapic_timer_frequency = ecx / HZ;
+		pr_info("Host bus clock speed read from hypervisor : %u Hz\n",
+			ecx);
+#endif
+	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
+	}
 }
 
 /*
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#1 lore raw

[tip:x86/urgent] x86/vmware: Skip lapic calibration on VMware

x86/vmware: Skip lapic calibration on VMware
Commit-ID:  b91688f528fe96e09d17e6d87c1b2805eb0c445e
Gitweb:     http://git.kernel.org/tip/b91688f528fe96e09d17e6d87c1b2805eb0c445e
Author:     Renat Valiullin <[email protected]>
AuthorDate: Tue, 4 Oct 2016 13:11:48 -0700
Committer:  Thomas Gleixner <[email protected]>
CommitDate: Wed, 5 Oct 2016 11:43:30 +0200

x86/vmware: Skip lapic calibration on VMware

In a virtualized environment the APIC timer calibration can go wrong when the host is overcommitted or the guest is running nested. This results in the APIC timers operating at an incorrect frequency.

Since VMware supports a mechanism to retrieve the local APIC frequency we can ask the hypervisor for it and skip the APIC calibration loop.

Signed-off-by Renat Valiullin <[email protected]>
Acked-by Alok N Kataria <[email protected]>
Cc [email protected]
Link http://lkml.kernel.org/r/20161004201148.GA1421@uu64vm open here
Signed-off-by Thomas Gleixner <[email protected]>
---
 arch/x86/kernel/cpu/vmware.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
arch/x86/kernel/cpu/vmware.c +10 -2
index 1ff0598..8116057 100644
@@ -27,6 +27,7 @@
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
+#include <asm/apic.h>
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868

@@ -82,10 +83,17 @@ static void __init vmware_platform_setup(void)
 
 	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
 
-	if (ebx != UINT_MAX)
+	if (ebx != UINT_MAX) {
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
-	else
+#ifdef CONFIG_X86_LOCAL_APIC
+		/* Skip lapic calibration since we know the bus frequency. */
+		lapic_timer_frequency = ecx / HZ;
+		pr_info("Host bus clock speed read from hypervisor : %u Hz\n",
+			ecx);
+#endif
+	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
+	}
 }
 
 /*