linux-kernel - [RFC PATCH 08/73] KVM: x86: Allow hypercall handling to not skip the instruction

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Message-Id: <20240226143630.33643-9-jiangshanlai@gmail.com>
Date: Mon, 26 Feb 2024 22:35:25 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Hou Wenlong <houwenlong.hwl@...group.com>,
	Lai Jiangshan <jiangshan.ljs@...group.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	x86@...nel.org,
	Kees Cook <keescook@...omium.org>,
	Juergen Gross <jgross@...e.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [RFC PATCH 08/73] KVM: x86: Allow hypercall handling to not skip the instruction

From: Hou Wenlong <houwenlong.hwl@...group.com>

In PVM, the syscall instruction is used as the hypercall instruction.
Since the syscall instruction is a trap that indicates the instruction
has been executed, there is no need to skip the hypercall instruction.

Suggested-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 arch/x86/include/asm/kvm_host.h | 12 +++++++++++-
 arch/x86/kvm/x86.c              | 10 +++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c76bafe9c7e2..d17d85106d6f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2077,7 +2077,17 @@ static inline void kvm_clear_apicv_inhibit(struct kvm *kvm,
 	kvm_set_or_clear_apicv_inhibit(kvm, reason, false);
 }
 
-int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
+int kvm_handle_hypercall(struct kvm_vcpu *vcpu, bool skip);
+
+static inline int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
+{
+	return kvm_handle_hypercall(vcpu, true);
+}
+
+static inline int kvm_emulate_hypercall_noskip(struct kvm_vcpu *vcpu)
+{
+	return kvm_handle_hypercall(vcpu, false);
+}
 
 int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
 		       void *insn, int insn_len);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 96f3913f7fc5..8ec7a36cdf3e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9933,7 +9933,7 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu)
 	return kvm_skip_emulated_instruction(vcpu);
 }
 
-int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
+int kvm_handle_hypercall(struct kvm_vcpu *vcpu, bool skip)
 {
 	unsigned long nr, a0, a1, a2, a3, ret;
 	int op_64_bit;
@@ -10034,9 +10034,13 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 	kvm_rax_write(vcpu, ret);
 
 	++vcpu->stat.hypercalls;
-	return kvm_skip_emulated_instruction(vcpu);
+
+	if (skip)
+		return kvm_skip_emulated_instruction(vcpu);
+
+	return 1;
 }
-EXPORT_SYMBOL_GPL(kvm_emulate_hypercall);
+EXPORT_SYMBOL_GPL(kvm_handle_hypercall);
 
 static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
 {
-- 
2.19.1.6.gb485710b