linux-kernel - [PATCH v2] KVM: x86: Fix poll command

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Date:   Thu, 13 Apr 2023 20:11:14 +0800
From:   alexjlzheng@...il.com
To:     seanjc@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jinliang Zheng <alexjlzheng@...cent.com>
Subject: [PATCH v2] KVM: x86: Fix poll command

From: Jinliang Zheng <alexjlzheng@...cent.com>

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():
1. Set Bit 7 when there is an interrupt
2. Return 0 when there is no interrupt

Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
---
Changes since Version V2:
- Keep the logic of pic_poll_read(), only fix the return value
---
 arch/x86/kvm/i8259.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 4756bcb5724f..6627f8a52f23 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -411,8 +411,9 @@ 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);
+		ret |= 0x80;
 	} else {
-		ret = 0x07;
+		ret = 0x00;
 		pic_update_irq(s->pics_state);
 	}
 
-- 
2.31.1