KVM: x86: Fix poll command

According to the hardware manual, when the Poll command is issued, the
byte returned by the I/O read is 1 in Bit 7 when there is an interrupt,
and the highest priority binary code in Bits 2:0. The current pic
simulation code is not implemented strictly according to the above
expression.

Fix the implementation of pic_poll_read(), set Bit 7 when there is an
interrupt.

Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
Link: https://lore.kernel.org/r/20230419021924.1342184-1-alexjlzheng@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 4756bcb..8dec646 100644 (file)
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -411,7 +411,10 @@ static u32 pic_poll_read(struct kvm_kpic_state *s, u32 addr1)
                pic_clear_isr(s, ret);
                if (addr1 >> 7 || ret != 2)
                        pic_update_irq(s->pics_state);
+               /* Bit 7 is 1, means there's an interrupt */
+               ret |= 0x80;
        } else {
+               /* Bit 7 is 0, means there's no interrupt */
                ret = 0x07;
                pic_update_irq(s->pics_state);
        }