linux-kernel - Re: [PATCH v1 2/2] LoongArch: KVM: Add lasx support

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Message-ID: <e907c7e2-ff54-e420-ae63-0d2c8481994f@loongson.cn>
Date:   Tue, 21 Nov 2023 20:17:57 +0800
From:   zhaotianrui <zhaotianrui@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     WANG Xuerui <kernel@...0n.name>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        loongarch@...ts.linux.dev, Jens Axboe <axboe@...nel.dk>,
        Mark Brown <broonie@...nel.org>,
        Alex Deucher <alexander.deucher@....com>,
        Oliver Upton <oliver.upton@...ux.dev>, maobibo@...ngson.cn,
        Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v1 2/2] LoongArch: KVM: Add lasx support


在 2023/11/21 下午7:55, Huacai Chen 写道:
> On Tue, Nov 21, 2023 at 5:59 PM zhaotianrui <zhaotianrui@...ngson.cn> wrote:
>>
>> 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@...ngson.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.
> To keep consistency it is better to export both.
>
> Huacai
Thanks, I will export both functions.

Tianrui Zhao
>
>> Thanks
>> Tianrui Zhao
>>