linux-kernel - [PATCH v4 2/6] KVM: x86: Add a helper to check for user interception of KVM hypercalls

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Message-ID: <20241128004344.4072099-3-seanjc@google.com>
Date: Wed, 27 Nov 2024 16:43:40 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Tom Lendacky <thomas.lendacky@....com>, Binbin Wu <binbin.wu@...ux.intel.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>, Kai Huang <kai.huang@...el.com>, 
	Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [PATCH v4 2/6] KVM: x86: Add a helper to check for user interception
 of KVM hypercalls

From: Binbin Wu <binbin.wu@...ux.intel.com>

Add and use user_exit_on_hypercall() to check if userspace wants to handle
a KVM hypercall instead of open-coding the logic everywhere.

No functional change intended.

Signed-off-by: Binbin Wu <binbin.wu@...ux.intel.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@...el.com>
Reviewed-by: Kai Huang <kai.huang@...el.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>
[sean: squash into one patch, keep explicit KVM_HC_MAP_GPA_RANGE check]
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 4 ++--
 arch/x86/kvm/x86.c     | 2 +-
 arch/x86/kvm/x86.h     | 5 +++++
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 72674b8825c4..6ac6312c4d57 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3640,7 +3640,7 @@ static int snp_begin_psc_msr(struct vcpu_svm *svm, u64 ghcb_msr)
 		return 1; /* resume guest */
 	}
 
-	if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE))) {
+	if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE)) {
 		set_ghcb_msr(svm, GHCB_MSR_PSC_RESP_ERROR);
 		return 1; /* resume guest */
 	}
@@ -3723,7 +3723,7 @@ static int snp_begin_psc(struct vcpu_svm *svm, struct psc_buffer *psc)
 	bool huge;
 	u64 gfn;
 
-	if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE))) {
+	if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE)) {
 		snp_complete_psc(svm, VMGEXIT_PSC_ERROR_GENERIC);
 		return 1;
 	}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0b2fe4aa04a2..13fe5d6eb8f3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10041,7 +10041,7 @@ unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
 		u64 gpa = a0, npages = a1, attrs = a2;
 
 		ret = -KVM_ENOSYS;
-		if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE)))
+		if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE))
 			break;
 
 		if (!PAGE_ALIGNED(gpa) || !npages ||
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index ec623d23d13d..45dd53284dbd 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -612,4 +612,9 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
 			 unsigned int port, void *data,  unsigned int count,
 			 int in);
 
+static inline bool user_exit_on_hypercall(struct kvm *kvm, unsigned long hc_nr)
+{
+	return kvm->arch.hypercall_exit_enabled & BIT(hc_nr);
+}
+
 #endif
-- 
2.47.0.338.g60cca15819-goog