[PATCH v2] KVM: RISC-V: Avoid spurious virtual interrupts after clearing hideleg CSR

From: Vincent Chen <vincent.chen@sifive.com>
To: anup.patel@wdc.com, atish.patra@wdc.com
Cc: palmer@dabbelt.com, paul.walmsley@sifive.com,
	kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
	Vincent Chen <vincent.chen@sifive.com>
Subject: [PATCH v2] KVM: RISC-V: Avoid spurious virtual interrupts after clearing hideleg CSR
Date: Mon, 27 Dec 2021 11:05:14 +0800	[thread overview]
Message-ID: <20211227030514.1426-1-vincent.chen@sifive.com> (raw)

When the last VM is terminated, the host kernel will invoke function
hardware_disable_nolock() on each CPU to disable the related virtualization
functions. Here, RISC-V currently only clears hideleg CSR and hedeleg CSR.
This behavior will cause the host kernel to receive spurious interrupts if
hvip CSR has pending interrupts and the corresponding enable bits in vsie
CSR are asserted. To avoid it, hvip CSR and vsie CSR must be cleared
before clearing hideleg CSR.

Fixes: 99cdc6c18c2d ("RISC-V: Add initial skeletal KVM support")
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/kvm/main.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index 421ecf4e6360..18e7a979740c 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -58,6 +58,14 @@ int kvm_arch_hardware_enable(void)
 
 void kvm_arch_hardware_disable(void)
 {
+	/*
+	 * After clearing the hideleg CSR, the host kernel will receive spurious
+	 * interrupts if hvip CSR has pending interrupts and the corresponding
+	 * enable bits in vsie CSR are asserted. To avoid it, hvip CSR and
+	 * vsie CSR must be cleared before clearing hideleg CSR.
+	 */
+	csr_write(CSR_VSIE, 0);
+	csr_write(CSR_HVIP, 0);
 	csr_write(CSR_HEDELEG, 0);
 	csr_write(CSR_HIDELEG, 0);
 }
-- 
2.17.1


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