linux-kernel - Re: [PATCH v2 3/8] KVM: TDX: Add a place holder for handler of TDX hypercalls (TDG.VP.VMCALL)

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Message-ID: <a771f116-d70e-4f52-ada3-8422e1f45acf@linux.intel.com>
Date: Wed, 12 Feb 2025 10:21:14 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>, Chao Gao <chao.gao@...el.com>
Cc: pbonzini@...hat.com, kvm@...r.kernel.org, rick.p.edgecombe@...el.com,
 kai.huang@...el.com, adrian.hunter@...el.com, reinette.chatre@...el.com,
 xiaoyao.li@...el.com, tony.lindgren@...el.com, isaku.yamahata@...el.com,
 yan.y.zhao@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/8] KVM: TDX: Add a place holder for handler of TDX
 hypercalls (TDG.VP.VMCALL)



On 2/12/2025 7:46 AM, Sean Christopherson wrote:
> On Tue, Feb 11, 2025, Chao Gao wrote:
>>> @@ -810,6 +829,7 @@ static bool tdx_guest_state_is_invalid(struct kvm_vcpu *vcpu)
>>> static __always_inline u32 tdx_to_vmx_exit_reason(struct kvm_vcpu *vcpu)
>>> {
>>> 	struct vcpu_tdx *tdx = to_tdx(vcpu);
>>> +	u32 exit_reason;
>>>
>>> 	switch (tdx->vp_enter_ret & TDX_SEAMCALL_STATUS_MASK) {
>>> 	case TDX_SUCCESS:
>>> @@ -822,7 +842,21 @@ static __always_inline u32 tdx_to_vmx_exit_reason(struct kvm_vcpu *vcpu)
>>> 		return -1u;
>>> 	}
>>>
>>> -	return tdx->vp_enter_ret;
>>> +	exit_reason = tdx->vp_enter_ret;
>>> +
>>> +	switch (exit_reason) {
>>> +	case EXIT_REASON_TDCALL:
>>> +		if (tdvmcall_exit_type(vcpu))
>>> +			return EXIT_REASON_VMCALL;
>>> +
>>> +		if (tdvmcall_leaf(vcpu) < 0x10000)
>> Can you add a comment for the hard-coded 0x10000?
> Or better yet, a #define of some kind (with a comment ;-) ).

As Chao pointed out, we should convert the leaves defined in the GHCI spec
and supported in KVM only.  Specific leaf numbers will be used instead of
comparing to 0x10000.

I plan to change it to:

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 2b24f50ad0ee..af8276402212 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -920,11 +920,17 @@ static __always_inline u32 tdx_to_vmx_exit_reason(struct kvm_vcpu *vcpu)
                 if (tdvmcall_exit_type(vcpu))
                         return EXIT_REASON_VMCALL;

-               if (tdvmcall_leaf(vcpu) < 0x10000) {
-                       if (tdvmcall_leaf(vcpu) == EXIT_REASON_EPT_VIOLATION)
+               switch(tdvmcall_leaf(vcpu)) {
+                       case EXIT_REASON_EPT_VIOLATION:
                                 return EXIT_REASON_EPT_MISCONFIG;
-
-                       return tdvmcall_leaf(vcpu);
+                       case EXIT_REASON_CPUID:
+                       case EXIT_REASON_HLT:
+                       case EXIT_REASON_IO_INSTRUCTION:
+                       case EXIT_REASON_MSR_READ:
+                       case EXIT_REASON_MSR_WRITE:
+                               return tdvmcall_leaf(vcpu);
+                       default:
+                               break;
                 }
                 break;
         case EXIT_REASON_EPT_MISCONFIG: