linux-kernel - Re: [PATCH] LoongArch: KVM: Reload guest CSR registers after S4

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Message-ID: <8f3ae3e5-6827-7c8d-2b80-726b56254ea1@loongson.cn>
Date: Tue, 4 Mar 2025 19:57:19 +0800
From: bibo mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>,
 kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Xianglai Li <lixianglai@...ngson.cn>
Subject: Re: [PATCH] LoongArch: KVM: Reload guest CSR registers after S4



On 2025/3/3 下午10:06, Huacai Chen wrote:
> Hi, Bibo,
> 
> On Mon, Mar 3, 2025 at 5:11 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> 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 register will reload from
>> scheduled vCPU context after suspend and resume.
>>
>> Also there is another small fix for Loongson AVEC support, bit 14 is added
>> in CSR ESTAT register. Macro CSR_ESTAT_IS is replaced with hardcoded value
>> 0x1fff and AVEC interrupt status bit 14 is supported with macro
>> CSR_ESTAT_IS.
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>>   arch/loongarch/kvm/main.c | 8 ++++++++
>>   arch/loongarch/kvm/vcpu.c | 2 +-
>>   2 files changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
>> index f6d3242b9234..b177773f38f6 100644
>> --- a/arch/loongarch/kvm/main.c
>> +++ b/arch/loongarch/kvm/main.c
>> @@ -284,6 +284,7 @@ long kvm_arch_dev_ioctl(struct file *filp,
>>   int kvm_arch_enable_virtualization_cpu(void)
>>   {
>>          unsigned long env, gcfg = 0;
>> +       struct kvm_context *context;
>>
>>          env = read_csr_gcfg();
>>
>> @@ -317,6 +318,13 @@ 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 register forced to reload
>> +        * from vCPU SW state
>> +        */
>> +       context = this_cpu_ptr(vmcs);
>> +       context->last_vcpu = NULL;
> This can be simplified as this_cpu_ptr(vmcs)->last_vcpu = NULL;
Sure, will do.
> 
>>          return 0;
>>   }
>>
>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>> index 20f941af3e9e..9e1a9b4aa4c6 100644
>> --- a/arch/loongarch/kvm/vcpu.c
>> +++ b/arch/loongarch/kvm/vcpu.c
>> @@ -311,7 +311,7 @@ static int kvm_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
>>   {
>>          int ret = RESUME_GUEST;
>>          unsigned long estat = vcpu->arch.host_estat;
>> -       u32 intr = estat & 0x1fff; /* Ignore NMI */
>> +       u32 intr = estat & CSR_ESTAT_IS;
> This part has nothing to do with S4, please split to another patch.
ok, will split into two patches.

Regards
Bibo Mao
> 
> Huacai
> 
>>          u32 ecode = (estat & CSR_ESTAT_EXC) >> CSR_ESTAT_EXC_SHIFT;
>>
>>          vcpu->mode = OUTSIDE_GUEST_MODE;
>>
>> base-commit: 1e15510b71c99c6e49134d756df91069f7d18141
>> --
>> 2.39.3
>>
>>