Commit 6bdbfe99 authored Nov 03, 2008 by Alok Kataria Committed by H. Peter Anvin Nov 03, 2008

x86: VMware: Fix vmware_get_tsc code



Impact: Fix possible failure to calibrate the TSC on Vmware near 4 GHz

The current version of the code to get the tsc frequency from
the VMware hypervisor, will be broken on processor with frequency
(4G-1) HZ, because on such processors eax will have UINT_MAX
and that would be legitimate.
We instead check that EBX did change to decide if we were able to
read the frequency from the hypervisor.

Signed-off-by: Alok N Kataria <akataria@vmware.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

parent 395628ef

arch/x86/kernel/cpu/vmware.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -36,7 +36,7 @@
		"=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) : \
		"0"(VMWARE_HYPERVISOR_MAGIC), \
		"1"(VMWARE_PORT_CMD_##cmd), \
		"2"(VMWARE_HYPERVISOR_PORT), "3"(0) : \
		"2"(VMWARE_HYPERVISOR_PORT), "3"(UINT_MAX) : \
		"memory");

		static inline int __vmware_platform(void)
		@@ -53,7 +53,7 @@ static unsigned long __vmware_get_tsc_khz(void)

		VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);

		if (eax == (uint32_t)-1)
		if (ebx == UINT_MAX)
		return 0;
		tsc_hz = eax \| (((uint64_t)ebx) << 32);
		do_div(tsc_hz, 1000);