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vircpuhost: Add support for reading MSRs
The new virHostCPUGetMSR internal API will try to read the MSR from /dev/cpu/0/msr and if it is not possible (the device does not exist or libvirt is running unprivileged), it will fallback to asking KVM for the MSR using KVM_GET_MSRS ioctl. Signed-off-by: Jiri Denemark <jdenemar@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com>
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@ -2027,6 +2027,7 @@ virHostCPUGetInfo;
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virHostCPUGetKVMMaxVCPUs;
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virHostCPUGetKVMMaxVCPUs;
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virHostCPUGetMap;
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virHostCPUGetMap;
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virHostCPUGetMicrocodeVersion;
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virHostCPUGetMicrocodeVersion;
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virHostCPUGetMSR;
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virHostCPUGetOnline;
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virHostCPUGetOnline;
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virHostCPUGetOnlineBitmap;
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virHostCPUGetOnlineBitmap;
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virHostCPUGetPresentBitmap;
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virHostCPUGetPresentBitmap;
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@ -58,6 +58,7 @@
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VIR_LOG_INIT("util.hostcpu");
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VIR_LOG_INIT("util.hostcpu");
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#define KVM_DEVICE "/dev/kvm"
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#define KVM_DEVICE "/dev/kvm"
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#define MSR_DEVICE "/dev/cpu/0/msr"
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#if defined(__FreeBSD__) || defined(__APPLE__)
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#if defined(__FreeBSD__) || defined(__APPLE__)
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@ -1254,3 +1255,82 @@ virHostCPUGetMicrocodeVersion(void)
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}
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}
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#endif /* __linux__ */
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#endif /* __linux__ */
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#if HAVE_LINUX_KVM_H && defined(KVM_GET_MSRS)
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static int
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virHostCPUGetMSRFromKVM(unsigned long index,
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uint64_t *result)
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{
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VIR_AUTOCLOSE fd = -1;
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struct {
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struct kvm_msrs header;
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struct kvm_msr_entry entry;
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} msr = {
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.header = { .nmsrs = 1 },
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.entry = { .index = index },
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};
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if ((fd = open(KVM_DEVICE, O_RDONLY)) < 0) {
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virReportSystemError(errno, _("Unable to open %s"), KVM_DEVICE);
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return -1;
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}
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if (ioctl(fd, KVM_GET_MSRS, &msr) < 0) {
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VIR_DEBUG("Cannot get MSR 0x%lx from KVM", index);
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return 1;
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}
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*result = msr.entry.data;
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return 0;
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}
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#else
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static int
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virHostCPUGetMSRFromKVM(unsigned long index ATTRIBUTE_UNUSED,
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uint64_t *result ATTRIBUTE_UNUSED)
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{
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virReportSystemError(ENOSYS, "%s",
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_("Reading MSRs via KVM is not supported on this platform"));
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return -1;
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}
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#endif /* HAVE_LINUX_KVM_H && defined(KVM_GET_MSRS) */
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/*
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* Returns 0 on success,
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* 1 when the MSR is not supported by the host CPU,
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* -1 on error.
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*/
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int
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virHostCPUGetMSR(unsigned long index,
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uint64_t *msr)
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{
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VIR_AUTOCLOSE fd = -1;
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char ebuf[1024];
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*msr = 0;
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if ((fd = open(MSR_DEVICE, O_RDONLY)) < 0) {
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VIR_DEBUG("Unable to open %s: %s",
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MSR_DEVICE, virStrerror(errno, ebuf, sizeof(ebuf)));
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} else {
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int rc = pread(fd, msr, sizeof(*msr), index);
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if (rc == sizeof(*msr))
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return 0;
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if (rc < 0 && errno == EIO) {
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VIR_DEBUG("CPU does not support MSR 0x%lx", index);
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return 1;
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}
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VIR_DEBUG("Cannot read MSR 0x%lx from %s: %s",
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index, MSR_DEVICE, virStrerror(errno, ebuf, sizeof(ebuf)));
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}
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VIR_DEBUG("Falling back to KVM ioctl");
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return virHostCPUGetMSRFromKVM(index, msr);
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}
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@ -66,4 +66,7 @@ int virHostCPUGetOnline(unsigned int cpu, bool *online);
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unsigned int virHostCPUGetMicrocodeVersion(void);
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unsigned int virHostCPUGetMicrocodeVersion(void);
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int virHostCPUGetMSR(unsigned long index,
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uint64_t *msr);
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#endif /* LIBVIRT_VIRHOSTCPU_H */
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#endif /* LIBVIRT_VIRHOSTCPU_H */
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