linux-kernel - [PATCH v3 1/2] KVM: x86: Check hypercall's exit to userspace generically

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Message-ID: <20240826022255.361406-2-binbin.wu@linux.intel.com>
Date: Mon, 26 Aug 2024 10:22:54 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: pbonzini@...hat.com,
	seanjc@...gle.com,
	isaku.yamahata@...el.com,
	rick.p.edgecombe@...el.com,
	kai.huang@...el.com,
	yuan.yao@...ux.intel.com,
	xiaoyao.li@...el.com,
	binbin.wu@...ux.intel.com
Subject: [PATCH v3 1/2] KVM: x86: Check hypercall's exit to userspace generically

Check whether a KVM hypercall needs to exit to userspace or not based on
hypercall_exit_enabled field of struct kvm_arch.

Userspace can request a hypercall to exit to userspace for handling by
enable KVM_CAP_EXIT_HYPERCALL and the enabled hypercall will be set in
hypercall_exit_enabled.  Make the check code generic based on it.

Signed-off-by: Binbin Wu <binbin.wu@...ux.intel.com>
Reviewed-by: Kai Huang <kai.huang@...el.com>
---
 arch/x86/kvm/x86.c | 5 +++--
 arch/x86/kvm/x86.h | 4 ++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 966fb301d44b..e521f14ad2b2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10220,8 +10220,9 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 	cpl = kvm_x86_call(get_cpl)(vcpu);
 
 	ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit, cpl);
-	if (nr == KVM_HC_MAP_GPA_RANGE && !ret)
-		/* MAP_GPA tosses the request to the user space. */
+	/* Check !ret first to make sure nr is a valid KVM hypercall. */
+	if (!ret && user_exit_on_hypercall(vcpu->kvm, nr))
+		/* The hypercall is requested to exit to userspace. */
 		return 0;
 
 	if (!op_64_bit)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 6556a43f1915..bc1a9e080acb 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -561,4 +561,8 @@ 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
-- 
2.46.0