linux-kernel - [PATCH 6/7] KVM: selftests: Verify guest debug DR7.GD checking during instruction emulation

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Message-Id: <0fc4f9d4aa0b1ed41cdeea1788d1d8907326d9b4.1757416809.git.houwenlong.hwl@antgroup.com>
Date: Wed, 10 Sep 2025 10:49:18 +0800
From: Hou Wenlong <houwenlong.hwl@...group.com>
To: kvm@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Shuah Khan <shuah@...nel.org>,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 6/7] KVM: selftests: Verify guest debug DR7.GD checking during instruction emulation

Similar to the global disable test case in x86's debug_regs test, use
'KVM_FEP' to trigger instruction emulation in order to verify the guest
debug DR7.GD checking during instruction emulation.

Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 tools/testing/selftests/kvm/x86/debug_regs.c | 25 +++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86/debug_regs.c b/tools/testing/selftests/kvm/x86/debug_regs.c
index 2d814c1d1dc4..ba80b77c2869 100644
--- a/tools/testing/selftests/kvm/x86/debug_regs.c
+++ b/tools/testing/selftests/kvm/x86/debug_regs.c
@@ -19,6 +19,7 @@
 uint32_t guest_value;
 
 extern unsigned char sw_bp, hw_bp, write_data, ss_start, bd_start;
+extern unsigned char fep_bd_start;
 
 static void guest_code(void)
 {
@@ -64,6 +65,12 @@ static void guest_code(void)
 
 	/* DR6.BD test */
 	asm volatile("bd_start: mov %%dr0, %%rax" : : : "rax");
+
+	if (is_forced_emulation_enabled) {
+		/* DR6.BD test for emulation */
+		asm volatile(KVM_FEP "fep_bd_start: mov %%dr0, %%rax" : : : "rax");
+	}
+
 	GUEST_DONE();
 }
 
@@ -185,7 +192,7 @@ int main(void)
 			    target_dr6);
 	}
 
-	/* Finally test global disable */
+	/* test global disable */
 	memset(&debug, 0, sizeof(debug));
 	debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP;
 	debug.arch.debugreg[7] = 0x400 | DR7_GD;
@@ -202,6 +209,22 @@ int main(void)
 			    run->debug.arch.pc, target_rip, run->debug.arch.dr6,
 			    target_dr6);
 
+	/* test global disable in emulation */
+	if (is_forced_emulation_enabled) {
+		/* Skip the 3-bytes "mov dr0" */
+		vcpu_skip_insn(vcpu, 3);
+		vcpu_run(vcpu);
+		TEST_ASSERT(run->exit_reason == KVM_EXIT_DEBUG &&
+			    run->debug.arch.exception == DB_VECTOR &&
+			    run->debug.arch.pc == CAST_TO_RIP(fep_bd_start) &&
+			    run->debug.arch.dr6 == target_dr6,
+			    "DR7.GD: exit %d exception %d rip 0x%llx "
+			    "(should be 0x%llx) dr6 0x%llx (should be 0x%llx)",
+			    run->exit_reason, run->debug.arch.exception,
+			    run->debug.arch.pc, target_rip, run->debug.arch.dr6,
+			    target_dr6);
+	}
+
 	/* Disable all debug controls, run to the end */
 	memset(&debug, 0, sizeof(debug));
 	vcpu_guest_debug_set(vcpu, &debug);
-- 
2.31.1