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Subject: Re: [PATCH v1 2/2] LoongArch: KVM: Add lasx support
To:     WANG Xuerui <kernel@xen0n.name>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        loongarch@lists.linux.dev, Jens Axboe <axboe@kernel.dk>,
        Mark Brown <broonie@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Oliver Upton <oliver.upton@linux.dev>, maobibo@loongson.cn,
        Xi Ruoyao <xry111@xry111.site>
References: <20231115091921.85516-1-zhaotianrui@loongson.cn>
 <20231115091921.85516-3-zhaotianrui@loongson.cn>
 <f003f38d-37fd-43ed-ada6-fb2d5b282e91@xen0n.name>
From:   zhaotianrui <zhaotianrui@loongson.cn>
Message-ID: <6d9395b5-e8f1-3990-adb0-a52d03411fc6@loongson.cn>
Date:   Tue, 21 Nov 2023 18:02:06 +0800
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在 2023/11/16 下午3:19, WANG Xuerui 写道:
> On 11/15/23 17:19, Tianrui Zhao wrote:
>> This patch adds LASX support for LoongArch KVM. The LASX means
>> LoongArch 256-bits vector instruction.
>> There will be LASX exception in KVM when guest use the LASX
>> instruction. KVM will enable LASX and restore the vector
>> registers for guest then return to guest to continue running.
>>
>> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
>> ---
>>   arch/loongarch/include/asm/kvm_host.h |  6 ++++
>>   arch/loongarch/include/asm/kvm_vcpu.h | 10 +++++++
>>   arch/loongarch/kernel/fpu.S           |  1 +
>>   arch/loongarch/kvm/exit.c             | 18 +++++++++++
>>   arch/loongarch/kvm/switch.S           | 16 ++++++++++
>>   arch/loongarch/kvm/trace.h            |  4 ++-
>>   arch/loongarch/kvm/vcpu.c             | 43 ++++++++++++++++++++++++++-
>>   7 files changed, 96 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/loongarch/include/asm/kvm_host.h 
>> b/arch/loongarch/include/asm/kvm_host.h
>> index 6c65c25169..4c05b5eca0 100644
>> --- a/arch/loongarch/include/asm/kvm_host.h
>> +++ b/arch/loongarch/include/asm/kvm_host.h
>> @@ -95,6 +95,7 @@ enum emulation_result {
>>   #define KVM_LARCH_SWCSR_LATEST    (0x1 << 1)
>>   #define KVM_LARCH_HWCSR_USABLE    (0x1 << 2)
>>   #define KVM_LARCH_LSX        (0x1 << 3)
>> +#define KVM_LARCH_LASX        (0x1 << 4)
>>     struct kvm_vcpu_arch {
>>       /*
>> @@ -181,6 +182,11 @@ static inline bool kvm_guest_has_lsx(struct 
>> kvm_vcpu_arch *arch)
>>       return arch->cpucfg[2] & CPUCFG2_LSX;
>>   }
>>   +static inline bool kvm_guest_has_lasx(struct kvm_vcpu_arch *arch)
>> +{
>> +    return arch->cpucfg[2] & CPUCFG2_LASX;
>> +}
>> +
>>   /* Debug: dump vcpu state */
>>   int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
>>   diff --git a/arch/loongarch/include/asm/kvm_vcpu.h 
>> b/arch/loongarch/include/asm/kvm_vcpu.h
>> index c629771e12..4f87f16018 100644
>> --- a/arch/loongarch/include/asm/kvm_vcpu.h
>> +++ b/arch/loongarch/include/asm/kvm_vcpu.h
>> @@ -67,6 +67,16 @@ static inline void kvm_restore_lsx(struct 
>> loongarch_fpu *fpu) { }
>>   static inline void kvm_restore_lsx_upper(struct loongarch_fpu *fpu) 
>> { }
>>   #endif
>>   +#ifdef CONFIG_CPU_HAS_LASX
>> +void kvm_own_lasx(struct kvm_vcpu *vcpu);
>> +void kvm_save_lasx(struct loongarch_fpu *fpu);
>> +void kvm_restore_lasx(struct loongarch_fpu *fpu);
>> +#else
>> +static inline void kvm_own_lasx(struct kvm_vcpu *vcpu) { }
>> +static inline void kvm_save_lasx(struct loongarch_fpu *fpu) { }
>> +static inline void kvm_restore_lasx(struct loongarch_fpu *fpu) { }
>> +#endif
>> +
>>   void kvm_acquire_timer(struct kvm_vcpu *vcpu);
>>   void kvm_init_timer(struct kvm_vcpu *vcpu, unsigned long hz);
>>   void kvm_reset_timer(struct kvm_vcpu *vcpu);
>> diff --git a/arch/loongarch/kernel/fpu.S b/arch/loongarch/kernel/fpu.S
>> index d53ab10f46..f4524fe866 100644
>> --- a/arch/loongarch/kernel/fpu.S
>> +++ b/arch/loongarch/kernel/fpu.S
>> @@ -384,6 +384,7 @@ SYM_FUNC_START(_restore_lasx_upper)
>>       lasx_restore_all_upper a0 t0 t1
>>       jr    ra
>>   SYM_FUNC_END(_restore_lasx_upper)
>> +EXPORT_SYMBOL(_restore_lasx_upper)
>
> Why the added export? It doesn't seem necessary, given the previous 
> patch doesn't have a similar export added for _restore_lsx_upper. (Or 
> if it's truly needed it should probably become EXPORT_SYMBOL_GPL.)
It is needed to be exported, as it is called by kvm_own_lasx. However 
the "_restore_lsx_upper" is not used in kvm.

Thanks
Tianrui Zhao