linux-kernel - [PATCH v2 1/2] LoongArch: KVM: Reload guest CSR registers after S4

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Message-Id: <20250306021840.2120016-2-maobibo@loongson.cn>
Date: Thu,  6 Mar 2025 10:18:39 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
	Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
	kvm@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Xianglai Li <lixianglai@...ngson.cn>
Subject: [PATCH v2 1/2] LoongArch: KVM: Reload guest CSR registers after S4

On host HW guest CSR registers are lost after suspend and resume
operation. Since last_vcpu of boot CPU still records latest vCPU pointer
so that guest CSR register skips to reload when boot CPU resumes and
vCPU is scheduled.

Here last_vcpu is cleared so that guest CSR registers will reload from
scheduled vCPU context after suspend and resume.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/loongarch/kvm/main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
index f6d3242b9234..af4d730196ef 100644
--- a/arch/loongarch/kvm/main.c
+++ b/arch/loongarch/kvm/main.c
@@ -317,6 +317,12 @@ int kvm_arch_enable_virtualization_cpu(void)
 	kvm_debug("GCFG:%lx GSTAT:%lx GINTC:%lx GTLBC:%lx",
 		  read_csr_gcfg(), read_csr_gstat(), read_csr_gintc(), read_csr_gtlbc());
 
+	/*
+	 * HW Guest CSR registers are lost after CPU suspend and resume.
+	 * Clear last_vcpu so that Guest CSR registers forced to reload
+	 * from vCPU SW state
+	 */
+	this_cpu_ptr(vmcs)->last_vcpu = NULL;
 	return 0;
 }
 
-- 
2.39.3