Re: [PATCH v4 14/19] KVM: VMX: Dump FRED context in dump_vmcs()

[Sean Christopherson <seanjc@google.com>]

On Fri, Mar 28, 2025, Xin Li (Intel) wrote:
> From: Xin Li <xin3.li@intel.com>
> 
> Add FRED related VMCS fields to dump_vmcs() to dump FRED context.
> 
> Signed-off-by: Xin Li <xin3.li@intel.com>
> Signed-off-by: Xin Li (Intel) <xin@zytor.com>
> Tested-by: Shan Kang <shan.kang@intel.com>
> ---
> 
> Change in v3:
> * Use (vmentry_ctrl & VM_ENTRY_LOAD_IA32_FRED) instead of is_fred_enabled()
>   (Chao Gao).
> 
> Changes in v2:
> * Use kvm_cpu_cap_has() instead of cpu_feature_enabled() (Chao Gao).
> * Dump guest FRED states only if guest has FRED enabled (Nikolay Borisov).
> ---
>  arch/x86/kvm/vmx/vmx.c | 40 +++++++++++++++++++++++++++++++++-------
>  1 file changed, 33 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index c76015e1e3f8..03855d6690b2 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6462,7 +6462,7 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  	u32 vmentry_ctl, vmexit_ctl;
>  	u32 cpu_based_exec_ctrl, pin_based_exec_ctrl, secondary_exec_control;
> -	u64 tertiary_exec_control;
> +	u64 tertiary_exec_control, secondary_vmexit_ctl;
>  	unsigned long cr4;
>  	int efer_slot;
>  
> @@ -6473,6 +6473,8 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
>  
>  	vmentry_ctl = vmcs_read32(VM_ENTRY_CONTROLS);
>  	vmexit_ctl = vmcs_read32(VM_EXIT_CONTROLS);
> +	secondary_vmexit_ctl = cpu_has_secondary_vmexit_ctrls() ?
> +			       vmcs_read64(SECONDARY_VM_EXIT_CONTROLS) : 0;
>  	cpu_based_exec_ctrl = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
>  	pin_based_exec_ctrl = vmcs_read32(PIN_BASED_VM_EXEC_CONTROL);
>  	cr4 = vmcs_readl(GUEST_CR4);
> @@ -6519,6 +6521,16 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
>  	vmx_dump_sel("LDTR:", GUEST_LDTR_SELECTOR);
>  	vmx_dump_dtsel("IDTR:", GUEST_IDTR_LIMIT);
>  	vmx_dump_sel("TR:  ", GUEST_TR_SELECTOR);
> +	if (vmentry_ctl & VM_ENTRY_LOAD_IA32_FRED)
> +		pr_err("FRED guest: config=0x%016llx, stack_levels=0x%016llx\n"
> +		       "RSP0=0x%016llx, RSP1=0x%016llx\n"
> +		       "RSP2=0x%016llx, RSP3=0x%016llx\n",
> +		       vmcs_read64(GUEST_IA32_FRED_CONFIG),
> +		       vmcs_read64(GUEST_IA32_FRED_STKLVLS),
> +		       __rdmsr(MSR_IA32_FRED_RSP0),

There is no guarantee the vCPU's FRED_RSP is loaded in hardware at this point.
I think you need to use vmx_read_guest_fred_rsp0().

> +		       vmcs_read64(GUEST_IA32_FRED_RSP1),
> +		       vmcs_read64(GUEST_IA32_FRED_RSP2),
> +		       vmcs_read64(GUEST_IA32_FRED_RSP3));
>  	efer_slot = vmx_find_loadstore_msr_slot(&vmx->msr_autoload.guest, MSR_EFER);
>  	if (vmentry_ctl & VM_ENTRY_LOAD_IA32_EFER)
>  		pr_err("EFER= 0x%016llx\n", vmcs_read64(GUEST_IA32_EFER));
> @@ -6566,6 +6578,16 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
>  	       vmcs_readl(HOST_TR_BASE));
>  	pr_err("GDTBase=%016lx IDTBase=%016lx\n",
>  	       vmcs_readl(HOST_GDTR_BASE), vmcs_readl(HOST_IDTR_BASE));
> +	if (vmexit_ctl & SECONDARY_VM_EXIT_LOAD_IA32_FRED)
> +		pr_err("FRED host: config=0x%016llx, stack_levels=0x%016llx\n"
> +		       "RSP0=0x%016lx, RSP1=0x%016llx\n"
> +		       "RSP2=0x%016llx, RSP3=0x%016llx\n",
> +		       vmcs_read64(HOST_IA32_FRED_CONFIG),
> +		       vmcs_read64(HOST_IA32_FRED_STKLVLS),
> +		       (unsigned long)task_stack_page(current) + THREAD_SIZE,

Maybe add a helper in arch/x86/include/asm/fred.h to generate the desired RSP0?
Not sure it's worth doing that just for this code.

> +		       vmcs_read64(HOST_IA32_FRED_RSP1),
> +		       vmcs_read64(HOST_IA32_FRED_RSP2),
> +		       vmcs_read64(HOST_IA32_FRED_RSP3));
>  	pr_err("CR0=%016lx CR3=%016lx CR4=%016lx\n",
>  	       vmcs_readl(HOST_CR0), vmcs_readl(HOST_CR3),
>  	       vmcs_readl(HOST_CR4));
> @@ -6587,25 +6609,29 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
>  	pr_err("*** Control State ***\n");
>  	pr_err("CPUBased=0x%08x SecondaryExec=0x%08x TertiaryExec=0x%016llx\n",
>  	       cpu_based_exec_ctrl, secondary_exec_control, tertiary_exec_control);
> -	pr_err("PinBased=0x%08x EntryControls=%08x ExitControls=%08x\n",
> -	       pin_based_exec_ctrl, vmentry_ctl, vmexit_ctl);
> +	pr_err("PinBased=0x%08x EntryControls=0x%08x\n",
> +	       pin_based_exec_ctrl, vmentry_ctl);
> +	pr_err("ExitControls=0x%08x SecondaryExitControls=0x%016llx\n",
> +	       vmexit_ctl, secondary_vmexit_ctl);
>  	pr_err("ExceptionBitmap=%08x PFECmask=%08x PFECmatch=%08x\n",
>  	       vmcs_read32(EXCEPTION_BITMAP),
>  	       vmcs_read32(PAGE_FAULT_ERROR_CODE_MASK),
>  	       vmcs_read32(PAGE_FAULT_ERROR_CODE_MATCH));
> -	pr_err("VMEntry: intr_info=%08x errcode=%08x ilen=%08x\n",
> +	pr_err("VMEntry: intr_info=%08x errcode=%08x ilen=%08x event_data=%016llx\n",
>  	       vmcs_read32(VM_ENTRY_INTR_INFO_FIELD),
>  	       vmcs_read32(VM_ENTRY_EXCEPTION_ERROR_CODE),
> -	       vmcs_read32(VM_ENTRY_INSTRUCTION_LEN));
> +	       vmcs_read32(VM_ENTRY_INSTRUCTION_LEN),
> +	       kvm_cpu_cap_has(X86_FEATURE_FRED) ? vmcs_read64(INJECTED_EVENT_DATA) : 0);
>  	pr_err("VMExit: intr_info=%08x errcode=%08x ilen=%08x\n",
>  	       vmcs_read32(VM_EXIT_INTR_INFO),
>  	       vmcs_read32(VM_EXIT_INTR_ERROR_CODE),
>  	       vmcs_read32(VM_EXIT_INSTRUCTION_LEN));
>  	pr_err("        reason=%08x qualification=%016lx\n",
>  	       vmcs_read32(VM_EXIT_REASON), vmcs_readl(EXIT_QUALIFICATION));
> -	pr_err("IDTVectoring: info=%08x errcode=%08x\n",
> +	pr_err("IDTVectoring: info=%08x errcode=%08x event_data=%016llx\n",
>  	       vmcs_read32(IDT_VECTORING_INFO_FIELD),
> -	       vmcs_read32(IDT_VECTORING_ERROR_CODE));
> +	       vmcs_read32(IDT_VECTORING_ERROR_CODE),
> +	       kvm_cpu_cap_has(X86_FEATURE_FRED) ? vmcs_read64(ORIGINAL_EVENT_DATA) : 0);
>  	pr_err("TSC Offset = 0x%016llx\n", vmcs_read64(TSC_OFFSET));
>  	if (secondary_exec_control & SECONDARY_EXEC_TSC_SCALING)
>  		pr_err("TSC Multiplier = 0x%016llx\n",
> -- 
> 2.48.1
>