linux-kernel - [PATCH 5.16 0808/1039] KVM: RISC-V: Avoid spurious virtual interrupts after clearing hideleg CSR

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Date:   Mon, 24 Jan 2022 19:43:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vincent Chen <vincent.chen@...ive.com>,
        Anup Patel <anup.patel@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0808/1039] KVM: RISC-V: Avoid spurious virtual interrupts after clearing hideleg CSR

From: Vincent Chen <vincent.chen@...ive.com>

[ Upstream commit 33e5b5746cc2336660c8710ba109d9a3923627b5 ]

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@...ive.com>
Reviewed-by: Anup Patel <anup.patel@....com>
Signed-off-by: Anup Patel <anup.patel@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 421ecf4e6360b..2e5ca43c8c49e 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);
 }
-- 
2.34.1