[kvm-unit-tests PATCH] x86: realmode: Test interrupt delivery after STI

[Roman Bolshakov <r.bolshakov@yadro.com>]

If interrupts are disabled, STI is inhibiting interrupts for the
instruction following it. If STI is followed by HLT, the CPU is going to
handle all pending or new interrupts as soon as HLT is executed.

Test if emulator properly clears inhibition state and allows the
scenario outlined above.

Cc: Cameron Esfahani <dirty@apple.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 x86/realmode.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/x86/realmode.c b/x86/realmode.c
index 31f84d0..3518224 100644
--- a/x86/realmode.c
+++ b/x86/realmode.c
@@ -814,6 +814,26 @@ static void test_int(void)
 	report("int 1", 0, 1);
 }
 
+static void test_sti_inhibit(void)
+{
+	init_inregs(NULL);
+
+	*(u32 *)(0x73 * 4) = 0x1000; /* Store IRQ 11 handler in the IDT */
+	*(u8 *)(0x1000) = 0xcf; /* 0x1000 contains an IRET instruction */
+
+	MK_INSN(sti_inhibit, "cli\n\t"
+			     "movw $0x200b, %dx\n\t"
+			     "movl $1, %eax\n\t"
+			     "outl %eax, %dx\n\t" /* Set IRQ11 */
+			     "movl $0, %eax\n\t"
+			     "outl %eax, %dx\n\t" /* Clear IRQ11 */
+			     "sti\n\t"
+			     "hlt\n\t");
+	exec_in_big_real_mode(&insn_sti_inhibit);
+
+	report("sti inhibit", ~0, 1);
+}
+
 static void test_imul(void)
 {
 	MK_INSN(imul8_1, "mov $2, %al\n\t"
@@ -1739,6 +1759,7 @@ void realmode_start(void)
 	test_xchg();
 	test_iret();
 	test_int();
+	test_sti_inhibit();
 	test_imul();
 	test_mul();
 	test_div();
-- 
2.24.1