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

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Message-ID: <CAAhV-H6Kq1gDvmAS9fnG4Lc4ot0H4tZftZvzSdd39fNjozo4bQ@mail.gmail.com>
Date:   Tue, 21 Nov 2023 19:55:19 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     zhaotianrui <zhaotianrui@...ngson.cn>
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

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
> Tianrui Zhao
>