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6bdbfe9991
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>
107 lines
3.3 KiB
C
107 lines
3.3 KiB
C
/*
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* VMware Detection code.
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*
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* Copyright (C) 2008, VMware, Inc.
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* Author : Alok N Kataria <akataria@vmware.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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*/
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#include <linux/dmi.h>
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#include <asm/div64.h>
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#define CPUID_VMWARE_INFO_LEAF 0x40000000
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#define VMWARE_HYPERVISOR_MAGIC 0x564D5868
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#define VMWARE_HYPERVISOR_PORT 0x5658
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#define VMWARE_PORT_CMD_GETVERSION 10
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#define VMWARE_PORT_CMD_GETHZ 45
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#define VMWARE_PORT(cmd, eax, ebx, ecx, edx) \
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__asm__("inl (%%dx)" : \
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"=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) : \
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"0"(VMWARE_HYPERVISOR_MAGIC), \
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"1"(VMWARE_PORT_CMD_##cmd), \
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"2"(VMWARE_HYPERVISOR_PORT), "3"(UINT_MAX) : \
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"memory");
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static inline int __vmware_platform(void)
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{
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uint32_t eax, ebx, ecx, edx;
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VMWARE_PORT(GETVERSION, eax, ebx, ecx, edx);
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return eax != (uint32_t)-1 && ebx == VMWARE_HYPERVISOR_MAGIC;
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}
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static unsigned long __vmware_get_tsc_khz(void)
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{
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uint64_t tsc_hz;
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uint32_t eax, ebx, ecx, edx;
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VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
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if (ebx == UINT_MAX)
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return 0;
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tsc_hz = eax | (((uint64_t)ebx) << 32);
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do_div(tsc_hz, 1000);
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BUG_ON(tsc_hz >> 32);
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return tsc_hz;
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}
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int vmware_platform(void)
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{
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if (cpu_has_hypervisor) {
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unsigned int eax, ebx, ecx, edx;
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char hyper_vendor_id[13];
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cpuid(CPUID_VMWARE_INFO_LEAF, &eax, &ebx, &ecx, &edx);
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memcpy(hyper_vendor_id + 0, &ebx, 4);
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memcpy(hyper_vendor_id + 4, &ecx, 4);
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memcpy(hyper_vendor_id + 8, &edx, 4);
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hyper_vendor_id[12] = '\0';
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if (!strcmp(hyper_vendor_id, "VMwareVMware"))
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return 1;
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} else if (dmi_available && dmi_name_in_vendors("VMware") &&
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__vmware_platform())
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return 1;
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return 0;
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}
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unsigned long vmware_get_tsc_khz(void)
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{
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BUG_ON(!vmware_platform());
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return __vmware_get_tsc_khz();
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}
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/*
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* VMware hypervisor takes care of exporting a reliable TSC to the guest.
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* Still, due to timing difference when running on virtual cpus, the TSC can
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* be marked as unstable in some cases. For example, the TSC sync check at
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* bootup can fail due to a marginal offset between vcpus' TSCs (though the
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* TSCs do not drift from each other). Also, the ACPI PM timer clocksource
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* is not suitable as a watchdog when running on a hypervisor because the
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* kernel may miss a wrap of the counter if the vcpu is descheduled for a
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* long time. To skip these checks at runtime we set these capability bits,
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* so that the kernel could just trust the hypervisor with providing a
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* reliable virtual TSC that is suitable for timekeeping.
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*/
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void __cpuinit vmware_set_feature_bits(struct cpuinfo_x86 *c)
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{
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set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
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set_cpu_cap(c, X86_FEATURE_TSC_RELIABLE);
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}
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