Hi Jan,
On 17.11.25 18:52, Jan Beulich wrote:
On 14.11.2025 15:22, Grygorii Strashko wrote:
--- a/xen/arch/x86/hvm/Kconfig
+++ b/xen/arch/x86/hvm/Kconfig
@@ -35,6 +35,18 @@ config INTEL_VMX
If your system includes a processor with Intel VT-x support, say Y.
If in doubt, say Y.
+config VMTRACE
+ bool "HW VM tracing support"
+ depends on INTEL_VMX
+ default y
+ help
+ Enables HW VM tracing support which allows to configure HW processor
+ features (vmtrace_op) to enable capturing information about software
+ execution using dedicated hardware facilities with minimal interference
+ to the software being traced. The trace data can be retrieved using
buffer
+ shared between Xen and domain
+ (see XENMEM_acquire_resource(XENMEM_resource_vmtrace_buf)).
Please check adjacent options above or ...
config HVM_FEP
bool "HVM Forced Emulation Prefix support (UNSUPPORTED)" if UNSUPPORTED
default DEBUG
... below for how proper indentation would look like here.
There is a mix in Kconfigs - some places <Tabs> some places <Spaces> :(
Will change to <Tabs>
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -307,6 +307,7 @@ static int vmx_init_vmcs_config(bool bsp)
rdmsrl(MSR_IA32_VMX_MISC, _vmx_misc_cap);
/* Check whether IPT is supported in VMX operation. */
+#ifdef CONFIG_VMTRACE
This imo wants to move ahead of the comment. (Feels a little like I may have
said so already, but it may well have been in the context of a different
recent patch.)
@@ -772,13 +775,24 @@ static inline int hvm_vmtrace_get_option(
return -EOPNOTSUPP;
}
+#else
+/*
+ * Function declaration(s) here are used without definition(s) to make compiler
+ * happy when VMTRACE=n, compiler DCE will eliminate unused code.
+ */
+int hvm_vmtrace_output_position(struct vcpu *v, uint64_t *pos);
+#endif
static inline int hvm_vmtrace_reset(struct vcpu *v)
{
+#ifdef CONFIG_VMTRACE
if ( hvm_funcs.vmtrace_reset )
return alternative_call(hvm_funcs.vmtrace_reset, v);
return -EOPNOTSUPP;
+#else
+ return -EOPNOTSUPP;
+#endif
No #else please and the #endif moved up.
--- a/xen/arch/x86/vm_event.c
+++ b/xen/arch/x86/vm_event.c
@@ -253,7 +253,8 @@ void vm_event_fill_regs(vm_event_request_t *req)
req->data.regs.x86.shadow_gs = ctxt.shadow_gs;
req->data.regs.x86.dr6 = ctxt.dr6;
- if ( hvm_vmtrace_output_position(curr, &req->data.regs.x86.vmtrace_pos) != 1 )
+ if ( IS_ENABLED(CONFIG_VMTRACE) &&
+ hvm_vmtrace_output_position(curr, &req->data.regs.x86.vmtrace_pos) !=
1 )
Would be nice if the too-long-line issue here was also address, when the line
needs touching anyway.
I left it as is for better readability as an exception.
Will below be ok:
if ( IS_ENABLED(CONFIG_VMTRACE) &&
- hvm_vmtrace_output_position(curr, &req->data.regs.x86.vmtrace_pos) !=
1 )
+ hvm_vmtrace_output_position(curr,
+ &req->data.regs.x86.vmtrace_pos) != 1 )
req->data.regs.x86.vmtrace_pos = ~0;
--
Best regards,
-grygorii
