Re: [PATCH v2] KVM: SVM: Convert plain error code numbers to defines

Melody (Huibo) Wang
2024-12-04T23:20:31Z

Hi Sean,

On 12/3/2024 4:50 PM, Sean Christopherson wrote:
> On Tue, Dec 03, 2024, Melody (Huibo) Wang wrote:
>> Hi Sean,
>>
>> On 12/2/2024 4:11 PM, Sean Christopherson wrote:
>>
>>>
>>> E.g. something like this? Definitely feel free to suggest better names.
>>>
>>> static inline void svm_vmgexit_set_return_code(struct vcpu_svm *svm,
>>> u64 response, u64 data)
>>> {
>>> ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, response);
>>> ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, data);
>>> }
>>>
>> If I make this function more generic where the exit info is set for both KVM
>> and the guest, then maybe I can write something like this:
>
> I like the idea, but I actually think it's better to keep the guest and host code
> separate in the case, because the guest code should actually set a triple, e.g.
>
> static __always_inline void sev_es_vmgexit_set_exit_info(struct ghcb *ghcb,
> u64 exit_code,
> u64 exit_info_1,
> u64 exit_info_2)
> {
> ghcb_set_sw_exit_code(ghcb, exit_code);
> ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
> ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
> }
>
> I'm not totally opposed to sharing code, but I think it will be counter-productive
> in this specific case. E.g. the guest version needs to be __always_inline so that
> it can be used in noinstr code.
>
>> void ghcb_set_exit_info(struct ghcb *ghcb,
>> u64 info1, u64 info2)
>> {
>> ghcb_set_sw_exit_info_1(ghcb, info1);
>> ghcb_set_sw_exit_info_2(ghcb, info2);
>>
>> }
>> This way we can address every possible case that sets the exit info - not only KVM.
>>
>> And I am not sure about the wrappers for each specific case because we will
>> have too many, too specific small functions, but if you want them I can add
>> them.
>
> I count three. We have far, far more wrappers VMX's is_exception_n(), and IMO
> those wrappers make the code significantly more readable.
Below is an untested yet conversion of the easy cases. I will take a look at converting the more complicated ones where not both exit info are set together, and see whether it looks more readable.

Thanks,
Melody

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e7db7a5703b7..0ed6bbdf949e 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3433,8 +3433,7 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
dump_ghcb(svm);
}

- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_MALFORMED_INPUT);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, reason);
+ svm_vmgexit_bad_input(svm, reason);

/* Resume the guest to "return" the error code. */
return 1;
@@ -3577,8 +3576,7 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
return 0;

e_scratch:
- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_MALFORMED_INPUT);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, GHCB_ERR_INVALID_SCRATCH_AREA);
+ svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_SCRATCH_AREA);

return 1;
}
@@ -4124,8 +4122,7 @@ static int snp_handle_ext_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t r
return snp_handle_guest_req(svm, req_gpa, resp_gpa);

request_invalid:
- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_MALFORMED_INPUT);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, GHCB_ERR_INVALID_INPUT);
+ svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT);
return 1; /* resume guest */
}

@@ -4317,8 +4314,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
if (ret)
return ret;

- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_SUCCESS);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, 0);
+ svm_vmgexit_success(svm, 0);

exit_code = kvm_ghcb_get_sw_exit_code(control);
switch (exit_code) {
@@ -4367,8 +4363,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
default:
pr_err("svm: vmgexit: unsupported AP jump table request - exit_info_1=%#llx\n",
control->exit_info_1);
- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_MALFORMED_INPUT);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, GHCB_ERR_INVALID_INPUT);
+ svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT);
}

ret = 1;
@@ -4397,8 +4392,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
case SVM_VMGEXIT_AP_CREATION:
ret = sev_snp_ap_creation(svm);
if (ret) {
- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_MALFORMED_INPUT);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, GHCB_ERR_INVALID_INPUT);
+ svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT);
}

ret = 1;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 58bce5f1ab0c..104e13d59c8a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2977,11 +2977,7 @@ static int svm_complete_emulated_msr(struct kvm_vcpu *vcpu, int err)
if (!err || !sev_es_guest(vcpu->kvm) || WARN_ON_ONCE(!svm->sev_es.ghcb))
return kvm_complete_insn_gp(vcpu, err);

- ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, GHCB_HV_RESP_ISSUE_EXCEPTION);
- ghcb_set_sw_exit_info_2(svm->sev_es.ghcb,
- X86_TRAP_GP |
- SVM_EVTINJ_TYPE_EXEPT |
- SVM_EVTINJ_VALID);
+ svm_vmgexit_inject_exception(svm, X86_TRAP_GP);
return 1;
}

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 43fa6a16eb19..baff8237c5c9 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -588,6 +588,30 @@ static inline bool is_vnmi_enabled(struct vcpu_svm *svm)
return false;
}

+static inline void svm_vmgexit_set_return_code(struct vcpu_svm *svm,
+ u64 response, u64 data)
+{
+ ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, response);
+ ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, data);
+}
+
+static inline void svm_vmgexit_inject_exception(struct vcpu_svm *svm, u8 vector)
+{
+ u64 data = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_EXEPT | vector;
+
+ svm_vmgexit_set_return_code(svm, GHCB_HV_RESP_ISSUE_EXCEPTION, data);
+}
+
+static inline void svm_vmgexit_bad_input(struct vcpu_svm *svm, u64 suberror)
+{
+ svm_vmgexit_set_return_code(svm, GHCB_HV_RESP_MALFORMED_INPUT, suberror);
+}
+
+static inline void svm_vmgexit_success(struct vcpu_svm *svm, u64 data)
+{
+ svm_vmgexit_set_return_code(svm, GHCB_HV_RESP_SUCCESS, data);
+}
+
/* svm.c */
#define MSR_INVALID 0xffffffffU