KVM: x86/PVM: Enhance exit reason handling for PVM hypercalls

Improve the handling of exit reasons for PVM hypercalls by adding more
specific exit reasons based on the type of PVM hypercall. This enables
a more fine-grained analysis of the performance and behavior of PVM-based
virtual machines.

The new exit reasons cover various PVM hypercall types, including
IRQ_WIN, IRQ_HALT, LOAD_PGTBL, TLB_FLUSH, TLB_FLUSH_CURRENT, TLB_INVLPG,
LOAD_GS, RDMSR, WRMSR, and LOAD_TLS. Providing specific exit reasons for
each of these hypercall types allows for better insights into the
performance characteristics of PVM-based virtual machines and helps
identify potential areas for optimization.

Moreover, this change benefits performance analysis tools, such as perf,
by allowing them to provide more detailed information about the execution
of PVM hypercalls. This improvement helps users gain a better understanding
of the performance bottlenecks in their virtualized environments and make
informed decisions about optimizing their systems.

Signed-off-by: Jinrong Liang <cloudliang@tencent.com>

Author: Jinrong Liang

arch/x86/kvm/pvm/pvm.c

@@ -2424,6 +2424,27 @@ static int pvm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	return 0;
 }
 
+static u32 pvm_get_hypercall_exit_reason(struct kvm_vcpu *vcpu)
+{
+	u32 hypercall_exit_code = kvm_rax_read(vcpu);
+
+	switch (hypercall_exit_code) {
+	case PVM_HC_IRQ_WIN:
+	case PVM_HC_IRQ_HALT:
+	case PVM_HC_LOAD_PGTBL:
+	case PVM_HC_TLB_FLUSH:
+	case PVM_HC_TLB_FLUSH_CURRENT:
+	case PVM_HC_TLB_INVLPG:
+	case PVM_HC_LOAD_GS:
+	case PVM_HC_RDMSR:
+	case PVM_HC_WRMSR:
+	case PVM_HC_LOAD_TLS:
+		return hypercall_exit_code;
+	default:
+		return PVM_EXIT_REASONS_HYPERCALL;
+	}
+}
+
 static u32 pvm_get_syscall_exit_reason(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_pvm *pvm = to_pvm(vcpu);
@@ -2435,7 +2456,7 @@ static u32 pvm_get_syscall_exit_reason(struct kvm_vcpu *vcpu)
 		else if (rip == pvm->msr_rets_rip_plus2)
 			return PVM_EXIT_REASONS_ERETS;
 		else
-			return PVM_EXIT_REASONS_HYPERCALL;
+			return pvm_get_hypercall_exit_reason(vcpu);
 	}
 
 	return PVM_EXIT_REASONS_SYSCALL;