> > From: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > > > > Intel Processor Trace virtualization can be work in one of 2 possible > > modes: > > > > a. System-Wide mode (default): > > When the host configures Intel PT to collect trace packets > > of the entire system, it can leave the relevant VMX controls > > clear to allow VMX-specific packets to provide information > > across VMX transitions. > > KVM guest will not aware this feature in this mode and both > > host and KVM guest trace will output to host buffer. > > > > b. Host-Guest mode: > > Host can configure trace-packet generation while in > > VMX non-root operation for guests and root operation > > for native executing normally. > > Intel PT will be exposed to KVM guest in this mode, and > > the trace output to respective buffer of host and guest. > > In this mode, tht status of PT will be saved and disabled > > before VM-entry and restored after VM-exit if trace > > a virtual machine. > > > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > > Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx> > > --- > > > +#define SECONDARY_EXEC_PT_USE_GPA 0x01000000 > > +#define VM_EXIT_CLEAR_IA32_RTIT_CTL 0x02000000 > > +#define VM_ENTRY_LOAD_IA32_RTIT_CTL 0x00040000 > > Where are all of these bits documented? I'm looking at the latest SDM, volume 3 (325384-067US), and none of these bits aredocumented > there. This part is in the " Intel® Architecture Instruction Set Extensions and Future Features Programming Reference" https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf > > > + GUEST_IA32_RTIT_CTL = 0x00002814, > > + GUEST_IA32_RTIT_CTL_HIGH = 0x00002815, > > Where is this VMCS field documented? > > > +/* Default is SYSTEM mode. */ > > +static int __read_mostly pt_mode = PT_MODE_SYSTEM; > > +module_param(pt_mode, int, S_IRUGO); > > As a module parameter, this doesn't allow much flexibility. Is it possible to make this decision per-VM, using a VM capability that can be set > by userspace? (In that case, it may make sense to have a module parameter which allows/disallows the per-VM capability.) It is a good idea from my point of view, I think it need more discussion and can be implement in next phase if have strong requirement. > > > > +static inline bool cpu_has_vmx_intel_pt(void) { > > + u64 vmx_msr; > > + > > + rdmsrl(MSR_IA32_VMX_MISC, vmx_msr); > > + return !!(vmx_msr & MSR_IA32_VMX_MISC_INTEL_PT); } > > Instead of the rdmsr here, wouldn't it be better to cache the IA32_VMX_MISC MSR in vmcs_config? > Nit: throughout this change, the '!!' isn't necessary when casting an integer type to bool. MSR_IA32_VMX_MISC is not read frequency and just read once in this patch set during initialization. Thanks, Luwei Kang
