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Message-ID: <b3fc2c52-4bc6-b46d-1f5a-83a37eb1204b@loongson.cn>
Date: Wed, 6 Dec 2023 09:33:15 +0800
From: maobibo <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Huacai Chen <chenhuacai@...nel.org>,
WANG Xuerui <kernel@...0n.name>,
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>
Subject: Re: [PATCH v2 2/2] LoongArch: KVM: Add LASX support
On 2023/12/1 下午4:46, Tianrui Zhao wrote:
> This patch adds LASX support for LoongArch KVM.
> 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 | 2 ++
> arch/loongarch/kvm/exit.c | 18 +++++++++++
> arch/loongarch/kvm/switch.S | 15 +++++++++
> arch/loongarch/kvm/trace.h | 4 ++-
> arch/loongarch/kvm/vcpu.c | 46 ++++++++++++++++++++++++++-
> 7 files changed, 99 insertions(+), 2 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index a53b47093f4..dc817481b30 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -97,6 +97,7 @@ 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 {
> /*
> @@ -183,6 +184,11 @@ 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 c629771e122..4f87f160185 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 d53ab10f464..4382e36ae3d 100644
> --- a/arch/loongarch/kernel/fpu.S
> +++ b/arch/loongarch/kernel/fpu.S
> @@ -349,6 +349,7 @@ SYM_FUNC_START(_restore_lsx_upper)
> lsx_restore_all_upper a0 t0 t1
> jr ra
> SYM_FUNC_END(_restore_lsx_upper)
> +EXPORT_SYMBOL(_restore_lsx_upper)
>
> SYM_FUNC_START(_init_lsx_upper)
> lsx_init_all_upper t1
> @@ -384,6 +385,7 @@ 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)
>
> SYM_FUNC_START(_init_lasx_upper)
> lasx_init_all_upper t1
> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> index 1b1c58ccc83..57bd5bf562a 100644
> --- a/arch/loongarch/kvm/exit.c
> +++ b/arch/loongarch/kvm/exit.c
> @@ -676,6 +676,23 @@ static int kvm_handle_lsx_disabled(struct kvm_vcpu *vcpu)
> return RESUME_GUEST;
> }
>
> +/*
> + * kvm_handle_lasx_disabled() - Guest used LASX while disabled in root.
> + * @vcpu: Virtual CPU context.
> + *
> + * Handle when the guest attempts to use LASX when it is disabled in the root
> + * context.
> + */
> +static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu)
> +{
> + if (!kvm_guest_has_lasx(&vcpu->arch))
> + kvm_queue_exception(vcpu, EXCCODE_INE, 0);
> + else
> + kvm_own_lasx(vcpu);
> +
> + return RESUME_GUEST;
> +}
> +
> /*
> * LoongArch KVM callback handling for unimplemented guest exiting
> */
> @@ -705,6 +722,7 @@ static exit_handle_fn kvm_fault_tables[EXCCODE_INT_START] = {
> [EXCCODE_TLBM] = kvm_handle_write_fault,
> [EXCCODE_FPDIS] = kvm_handle_fpu_disabled,
> [EXCCODE_LSXDIS] = kvm_handle_lsx_disabled,
> + [EXCCODE_LASXDIS] = kvm_handle_lasx_disabled,
> [EXCCODE_GSPR] = kvm_handle_gspr,
> };
>
> diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
> index 6c48f7d1ca5..215c70b2de3 100644
> --- a/arch/loongarch/kvm/switch.S
> +++ b/arch/loongarch/kvm/switch.S
> @@ -266,6 +266,21 @@ SYM_FUNC_START(kvm_restore_lsx_upper)
> SYM_FUNC_END(kvm_restore_lsx_upper)
> #endif
>
> +#ifdef CONFIG_CPU_HAS_LASX
> +SYM_FUNC_START(kvm_save_lasx)
> + fpu_save_csr a0 t1
> + fpu_save_cc a0 t1 t2
> + lasx_save_data a0 t1
> + jr ra
> +SYM_FUNC_END(kvm_save_lasx)
> +
> +SYM_FUNC_START(kvm_restore_lasx)
> + lasx_restore_data a0 t1
> + fpu_restore_cc a0 t1 t2
> + fpu_restore_csr a0 t1 t2
> + jr ra
> +SYM_FUNC_END(kvm_restore_lasx)
> +#endif
> .section ".rodata"
> SYM_DATA(kvm_exception_size, .quad kvm_exc_entry_end - kvm_exc_entry)
> SYM_DATA(kvm_enter_guest_size, .quad kvm_enter_guest_end - kvm_enter_guest)
> diff --git a/arch/loongarch/kvm/trace.h b/arch/loongarch/kvm/trace.h
> index 7da4e230e89..c2484ad4cff 100644
> --- a/arch/loongarch/kvm/trace.h
> +++ b/arch/loongarch/kvm/trace.h
> @@ -103,6 +103,7 @@ TRACE_EVENT(kvm_exit_gspr,
>
> #define KVM_TRACE_AUX_FPU 1
> #define KVM_TRACE_AUX_LSX 2
> +#define KVM_TRACE_AUX_LASX 3
>
> #define kvm_trace_symbol_aux_op \
> { KVM_TRACE_AUX_SAVE, "save" }, \
> @@ -113,7 +114,8 @@ TRACE_EVENT(kvm_exit_gspr,
>
> #define kvm_trace_symbol_aux_state \
> { KVM_TRACE_AUX_FPU, "FPU" }, \
> - { KVM_TRACE_AUX_LSX, "LSX" }
> + { KVM_TRACE_AUX_LSX, "LSX" }, \
> + { KVM_TRACE_AUX_LASX, "LASX" }
>
> TRACE_EVENT(kvm_aux,
> TP_PROTO(struct kvm_vcpu *vcpu, unsigned int op,
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index 4820c95091f..7802ae68197 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -329,6 +329,13 @@ static int kvm_get_cpucfg_supported(int id, u64 *v)
> */
> if (cpu_has_lsx)
> *v |= CPUCFG2_LSX;
> + /*
> + * if LASX is supported by CPU, it is also supported by KVM,
> + * as we implement it.
> + */
> + if (cpu_has_lasx)
> + *v |= CPUCFG2_LASX;
> +
> break;
> default:
> ret = -EINVAL;
> @@ -653,12 +660,49 @@ void kvm_own_lsx(struct kvm_vcpu *vcpu)
> }
> #endif
>
> +#ifdef CONFIG_CPU_HAS_LASX
> +/* Enable LASX for guest and restore context */
> +void kvm_own_lasx(struct kvm_vcpu *vcpu)
> +{
> + preempt_disable();
> +
> + set_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
> + switch (vcpu->arch.aux_inuse & (KVM_LARCH_FPU | KVM_LARCH_LSX)) {
> + case KVM_LARCH_LSX | KVM_LARCH_FPU:
> + case KVM_LARCH_LSX:
> + /* Guest LSX state already loaded, only restore upper LASX state */
> + _restore_lasx_upper(&vcpu->arch.fpu);
> + break;
> + case KVM_LARCH_FPU:
> + /* Guest FP state already loaded, only restore 64~256 LASX state */
> + kvm_restore_lsx_upper(&vcpu->arch.fpu);
> + _restore_lasx_upper(&vcpu->arch.fpu);
> + break;
> + default:
> + /* Neither FP or LSX already active, restore full LASX state */
> + kvm_restore_lasx(&vcpu->arch.fpu);
> + break;
> + }
> +
> + trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LASX);
> + vcpu->arch.aux_inuse |= KVM_LARCH_LASX | KVM_LARCH_LSX | KVM_LARCH_FPU;
> + preempt_enable();
> +}
> +#endif
> +
> /* Save context and disable FPU */
> void kvm_lose_fpu(struct kvm_vcpu *vcpu)
> {
> preempt_disable();
>
> - if (vcpu->arch.aux_inuse & KVM_LARCH_LSX) {
> + if (vcpu->arch.aux_inuse & KVM_LARCH_LASX) {
> + kvm_save_lasx(&vcpu->arch.fpu);
> + vcpu->arch.aux_inuse &= ~(KVM_LARCH_LSX | KVM_LARCH_FPU | KVM_LARCH_LASX);
> + trace_kvm_aux(vcpu, KVM_TRACE_AUX_SAVE, KVM_TRACE_AUX_LASX);
> +
> + /* Disable LASX & LSX & FPU */
> + clear_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
> + } else if (vcpu->arch.aux_inuse & KVM_LARCH_LSX) {
> kvm_save_lsx(&vcpu->arch.fpu);
> vcpu->arch.aux_inuse &= ~(KVM_LARCH_LSX | KVM_LARCH_FPU);
> trace_kvm_aux(vcpu, KVM_TRACE_AUX_SAVE, KVM_TRACE_AUX_LSX);
>
Reviewed-by: Bibo Mao <maobibo@...ngson.cn>
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