In the x86's debug_regs test, add a test case to cover the scenario where
single-step with STI in VMX sets the 'BS' bit in pending debug
exceptions for #DB interception and instruction emulation in both cases.

Signed-off-by: Hou Wenlong <houwenlong....@antgroup.com>
---
 .../selftests/kvm/include/x86/processor.h     |  3 +-
 tools/testing/selftests/kvm/x86/debug_regs.c  | 41 +++++++++++++++++--
 2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86/processor.h 
b/tools/testing/selftests/kvm/include/x86/processor.h
index 488d516c4f6f..f5827cca813e 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -34,7 +34,8 @@ extern uint64_t guest_tsc_khz;
 
 #define NMI_VECTOR             0x02
 
-#define X86_EFLAGS_FIXED        (1u << 1)
+#define X86_EFLAGS_FIXED       (1u << 1)
+#define X86_EFLAGS_TF          (1u << 8)
 
 #define X86_CR4_VME            (1ul << 0)
 #define X86_CR4_PVI            (1ul << 1)
diff --git a/tools/testing/selftests/kvm/x86/debug_regs.c 
b/tools/testing/selftests/kvm/x86/debug_regs.c
index ba80b77c2869..60dea0116b21 100644
--- a/tools/testing/selftests/kvm/x86/debug_regs.c
+++ b/tools/testing/selftests/kvm/x86/debug_regs.c
@@ -15,11 +15,31 @@
 
 #define IRQ_VECTOR 0xAA
 
+#define  CAST_TO_RIP(v)  ((unsigned long long)&(v))
+
 /* For testing data access debug BP */
 uint32_t guest_value;
 
 extern unsigned char sw_bp, hw_bp, write_data, ss_start, bd_start;
-extern unsigned char fep_bd_start;
+extern unsigned char fep_bd_start, fep_sti_start, fep_sti_end;
+
+static void guest_db_handler(struct ex_regs *regs)
+{
+       static int count;
+       unsigned long target_rips[2] = {
+               CAST_TO_RIP(fep_sti_start),
+               CAST_TO_RIP(fep_sti_end),
+       };
+
+       __GUEST_ASSERT(regs->rip == target_rips[count], "STI: unexpected rip 
0x%lx (should be 0x%lx)",
+                      regs->rip, target_rips[count]);
+       regs->rflags &= ~X86_EFLAGS_TF;
+       count++;
+}
+
+static void guest_irq_handler(struct ex_regs *regs)
+{
+}
 
 static void guest_code(void)
 {
@@ -69,13 +89,25 @@ static void guest_code(void)
        if (is_forced_emulation_enabled) {
                /* DR6.BD test for emulation */
                asm volatile(KVM_FEP "fep_bd_start: mov %%dr0, %%rax" : : : 
"rax");
+
+               /* pending debug exceptions for emulation */
+               asm volatile("pushf\n\t"
+                            "orq $" __stringify(X86_EFLAGS_TF) ", (%rsp)\n\t"
+                            "popf\n\t"
+                            "sti\n\t"
+                            "fep_sti_start:"
+                            "cli\n\t"
+                            "pushf\n\t"
+                            "orq $" __stringify(X86_EFLAGS_TF) ", (%rsp)\n\t"
+                            "popf\n\t"
+                            KVM_FEP "sti\n\t"
+                            "fep_sti_end:"
+                            "cli\n\t");
        }
 
        GUEST_DONE();
 }
 
-#define  CAST_TO_RIP(v)  ((unsigned long long)&(v))
-
 static void vcpu_skip_insn(struct kvm_vcpu *vcpu, int insn_len)
 {
        struct kvm_regs regs;
@@ -110,6 +142,9 @@ int main(void)
        vm = vm_create_with_one_vcpu(&vcpu, guest_code);
        run = vcpu->run;
 
+       vm_install_exception_handler(vm, DB_VECTOR, guest_db_handler);
+       vm_install_exception_handler(vm, IRQ_VECTOR, guest_irq_handler);
+
        /* Test software BPs - int3 */
        memset(&debug, 0, sizeof(debug));
        debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
-- 
2.31.1


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