linux-kernel - [RFC PATCH 36/73] KVM: x86/PVM: Handle KVM hypercall

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Date: Mon, 26 Feb 2024 22:35:53 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
	Hou Wenlong <houwenlong.hwl@...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 36/73] KVM: x86/PVM: Handle KVM hypercall

From: Lai Jiangshan <jiangshan.ljs@...group.com>

PVM uses the syscall instruction as the hypercall instruction, so r10 is
used as a replacement for rcx since rcx is clobbered by the syscall.
Additionally, the syscall is a trap and does not need to skip the
hypercall instruction for PVM.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/kvm/pvm/pvm.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pvm/pvm.c b/arch/x86/kvm/pvm/pvm.c
index a2602d9828a5..242c355fda8f 100644
--- a/arch/x86/kvm/pvm/pvm.c
+++ b/arch/x86/kvm/pvm/pvm.c
@@ -1221,6 +1221,18 @@ static int handle_synthetic_instruction_return_supervisor(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int handle_kvm_hypercall(struct kvm_vcpu *vcpu)
+{
+	int r;
+
+	// In PVM, r10 is the replacement for rcx in hypercall
+	kvm_rcx_write(vcpu, kvm_r10_read(vcpu));
+	r = kvm_emulate_hypercall_noskip(vcpu);
+	kvm_r10_write(vcpu, kvm_rcx_read(vcpu));
+
+	return r;
+}
+
 static int handle_exit_syscall(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_pvm *pvm = to_pvm(vcpu);
@@ -1233,7 +1245,8 @@ static int handle_exit_syscall(struct kvm_vcpu *vcpu)
 		return handle_synthetic_instruction_return_user(vcpu);
 	if (rip == pvm->msr_rets_rip_plus2)
 		return handle_synthetic_instruction_return_supervisor(vcpu);
-	return 1;
+
+	return handle_kvm_hypercall(vcpu);
 }
 
 static int handle_exit_debug(struct kvm_vcpu *vcpu)
-- 
2.19.1.6.gb485710b