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LoongArch: KVM: Move host CSR_GSTAT save and restore in context switch

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CSR register LOONGARCH_CSR_GSTAT stores guest VMID information. With
existing implementation method, VMID is per vCPU, similar with ASID in
kernel. LOONGARCH_CSR_GSTAT is written at VM entry even if VMID is not
changed.

Here move LOONGARCH_CSR_GSTAT save/restore in vCPU context switch, and
update LOONGARCH_CSR_GSTAT only when VMID is updated at VM entry. At
most time VM enter/exit is much more frequent than vCPU thread context
switch.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Bibo Mao
2026-04-09 18:56:36 +08:00
committed by Huacai Chen
parent f62eb9ca8d
commit aac656857e
2 changed files with 6 additions and 4 deletions
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8
arch/loongarch/kvm/main.c
View File

@@ -271,11 +271,11 @@ void kvm_check_vpid(struct kvm_vcpu *vcpu)
* memory with new address is changed on other VCPUs.
*/
set_gcsr_llbctl(CSR_LLBCTL_WCLLB);
}
/* Restore GSTAT(0x50).vpid */
vpid = (vcpu->arch.vpid & vpid_mask) << CSR_GSTAT_GID_SHIFT;
change_csr_gstat(vpid_mask << CSR_GSTAT_GID_SHIFT, vpid);
/* Restore GSTAT(0x50).vpid */
vpid = (vcpu->arch.vpid & vpid_mask) << CSR_GSTAT_GID_SHIFT;
change_csr_gstat(vpid_mask << CSR_GSTAT_GID_SHIFT, vpid);
}
}
void kvm_init_vmcs(struct kvm *kvm)

2
arch/loongarch/kvm/vcpu.c
View File

@@ -1699,6 +1699,7 @@ static int _kvm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
/* Restore Root.GINTC from unused Guest.GINTC register */
write_csr_gintc(csr->csrs[LOONGARCH_CSR_GINTC]);
write_csr_gstat(csr->csrs[LOONGARCH_CSR_GSTAT]);
/*
* We should clear linked load bit to break interrupted atomics. This
@@ -1794,6 +1795,7 @@ static int _kvm_vcpu_put(struct kvm_vcpu *vcpu, int cpu)
kvm_save_hw_gcsr(csr, LOONGARCH_CSR_ISR3);
}
csr->csrs[LOONGARCH_CSR_GSTAT] = read_csr_gstat();
vcpu->arch.aux_inuse |= KVM_LARCH_SWCSR_LATEST;
out: