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Commit b91688f5 authored by Renat Valiullin's avatar Renat Valiullin Committed by Thomas Gleixner
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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: default avatarRenat Valiullin <rvaliullin@vmware.com>
Acked-by: default avatarAlok N Kataria <akataria@vmware.com>
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20161004201148.GA1421@uu64vm


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 2df0e78b

arch/x86/kernel/cpu/vmware.c

+10 −2
Original line number Diff line number Diff line
@@ -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
@@ -82,11 +83,18 @@ 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");

	}

}



/*

 * While checking the dmi string information, just checking the product