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>
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 2ac4394..a0905ec 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -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 @@
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);