[PATCH v7 04/23] target/riscv: Improve delivery of guest external interrupts

From: Anup Patel <anup@brainfault.org>
To: Peter Maydell <peter.maydell@linaro.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Alistair Francis <Alistair.Francis@wdc.com>,
	Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: qemu-riscv@nongnu.org, Frank Chang <frank.chang@sifive.com>,
	Anup Patel <anup@brainfault.org>,
	qemu-devel@nongnu.org,
	Alistair Francis <alistair.francis@wdc.com>,
	Atish Patra <atishp@atishpatra.org>,
	Bin Meng <bmeng.cn@gmail.com>
Subject: [PATCH v7 04/23] target/riscv: Improve delivery of guest external interrupts
Date: Mon, 17 Jan 2022 18:58:07 +0530	[thread overview]
Message-ID: <20220117132826.426418-5-anup@brainfault.org> (raw)
In-Reply-To: <20220117132826.426418-1-anup@brainfault.org>

From: Anup Patel <anup.patel@wdc.com>

The guest external interrupts from an interrupt controller are
delivered only when the Guest/VM is running (i.e. V=1). This means
any guest external interrupt which is triggered while the Guest/VM
is not running (i.e. V=0) will be missed on QEMU resulting in Guest
with sluggish response to serial console input and other I/O events.

To solve this, we check and inject interrupt after setting V=1.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
---
 target/riscv/cpu_helper.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index aabf0a02f9..01a8baea06 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -325,6 +325,19 @@ void riscv_cpu_set_virt_enabled(CPURISCVState *env, bool enable)
     }
 
     env->virt = set_field(env->virt, VIRT_ONOFF, enable);
+
+    if (enable) {
+       /*
+        * The guest external interrupts from an interrupt controller are
+        * delivered only when the Guest/VM is running (i.e. V=1). This means
+        * any guest external interrupt which is triggered while the Guest/VM
+        * is not running (i.e. V=0) will be missed on QEMU resulting in guest
+        * with sluggish response to serial console input and other I/O events.
+        *
+        * To solve this, we check and inject interrupt after setting V=1.
+        */
+        riscv_cpu_update_mip(env_archcpu(env), 0, 0);
+    }
 }
 
 bool riscv_cpu_two_stage_lookup(int mmu_idx)
-- 
2.25.1


