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Date: Mon, 20 Nov 2023 09:31:04 +0800
From: zhaotianrui <zhaotianrui@...ngson.cn>
To: maobibo <maobibo@...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>,
Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v1 1/2] LoongArch: KVM: Add lsx support
在 2023/11/17 下午4:24, maobibo 写道:
>
>
> On 2023/11/15 下午5:19, Tianrui Zhao wrote:
>> This patch adds LSX support for LoongArch KVM. The LSX means
>> LoongArch 128-bits vector instruction.
>> There will be LSX exception in KVM when guest use the LSX
>> instruction. KVM will enable LSX 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 | 12 +++++++
>> arch/loongarch/kvm/exit.c | 18 ++++++++++
>> arch/loongarch/kvm/switch.S | 22 +++++++++++++
>> arch/loongarch/kvm/trace.h | 4 ++-
>> arch/loongarch/kvm/vcpu.c | 47 +++++++++++++++++++++++++--
>> 6 files changed, 105 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/loongarch/include/asm/kvm_host.h
>> b/arch/loongarch/include/asm/kvm_host.h
>> index 11328700d4..6c65c25169 100644
>> --- a/arch/loongarch/include/asm/kvm_host.h
>> +++ b/arch/loongarch/include/asm/kvm_host.h
>> @@ -94,6 +94,7 @@ enum emulation_result {
>> #define KVM_LARCH_FPU (0x1 << 0)
>> #define KVM_LARCH_SWCSR_LATEST (0x1 << 1)
>> #define KVM_LARCH_HWCSR_USABLE (0x1 << 2)
>> +#define KVM_LARCH_LSX (0x1 << 3)
>> struct kvm_vcpu_arch {
>> /*
>> @@ -175,6 +176,11 @@ static inline void writel_sw_gcsr(struct
>> loongarch_csrs *csr, int reg, unsigned
>> csr->csrs[reg] = val;
>> }
>> +static inline bool kvm_guest_has_lsx(struct kvm_vcpu_arch *arch)
>> +{
>> + return arch->cpucfg[2] & CPUCFG2_LSX;
>> +}
>> +
>> /* 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 553cfa2b2b..c629771e12 100644
>> --- a/arch/loongarch/include/asm/kvm_vcpu.h
>> +++ b/arch/loongarch/include/asm/kvm_vcpu.h
>> @@ -55,6 +55,18 @@ void kvm_save_fpu(struct loongarch_fpu *fpu);
>> void kvm_restore_fpu(struct loongarch_fpu *fpu);
>> void kvm_restore_fcsr(struct loongarch_fpu *fpu);
>> +#ifdef CONFIG_CPU_HAS_LSX
>> +void kvm_own_lsx(struct kvm_vcpu *vcpu);
>> +void kvm_save_lsx(struct loongarch_fpu *fpu);
>> +void kvm_restore_lsx(struct loongarch_fpu *fpu);
>> +void kvm_restore_lsx_upper(struct loongarch_fpu *fpu);
>> +#else
>> +static inline void kvm_own_lsx(struct kvm_vcpu *vcpu) { }
>> +static inline void kvm_save_lsx(struct loongarch_fpu *fpu) { }
>> +static inline void kvm_restore_lsx(struct loongarch_fpu *fpu) { }
>> +static inline void kvm_restore_lsx_upper(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/kvm/exit.c b/arch/loongarch/kvm/exit.c
>> index ce8de3fa47..1b1c58ccc8 100644
>> --- a/arch/loongarch/kvm/exit.c
>> +++ b/arch/loongarch/kvm/exit.c
>> @@ -659,6 +659,23 @@ static int kvm_handle_fpu_disabled(struct
>> kvm_vcpu *vcpu)
>> return RESUME_GUEST;
>> }
>> +/*
>> + * kvm_handle_lsx_disabled() - Guest used LSX while disabled in root.
>> + * @vcpu: Virtual CPU context.
>> + *
>> + * Handle when the guest attempts to use LSX when it is disabled in
>> the root
>> + * context.
>> + */
>> +static int kvm_handle_lsx_disabled(struct kvm_vcpu *vcpu)
>> +{
>> + if (!kvm_guest_has_lsx(&vcpu->arch))
>> + kvm_queue_exception(vcpu, EXCCODE_INE, 0);
>> + else
>> + kvm_own_lsx(vcpu);
>> +
>> + return RESUME_GUEST;
>> +}
>> +
>> /*
>> * LoongArch KVM callback handling for unimplemented guest exiting
>> */
>> @@ -687,6 +704,7 @@ static exit_handle_fn
>> kvm_fault_tables[EXCCODE_INT_START] = {
>> [EXCCODE_TLBS] = kvm_handle_write_fault,
>> [EXCCODE_TLBM] = kvm_handle_write_fault,
>> [EXCCODE_FPDIS] = kvm_handle_fpu_disabled,
>> + [EXCCODE_LSXDIS] = kvm_handle_lsx_disabled,
>> [EXCCODE_GSPR] = kvm_handle_gspr,
>> };
>> diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
>> index 0ed9040307..32ba092a44 100644
>> --- a/arch/loongarch/kvm/switch.S
>> +++ b/arch/loongarch/kvm/switch.S
>> @@ -245,6 +245,28 @@ SYM_FUNC_START(kvm_restore_fpu)
>> jr ra
>> SYM_FUNC_END(kvm_restore_fpu)
>> +#ifdef CONFIG_CPU_HAS_LSX
>> +SYM_FUNC_START(kvm_save_lsx)
>> + fpu_save_csr a0 t1
>> + fpu_save_cc a0 t1 t2
>> + lsx_save_data a0 t1
>> + jirl zero, ra, 0
>> +SYM_FUNC_END(kvm_save_lsx)
>> +
>> +SYM_FUNC_START(kvm_restore_lsx)
>> + lsx_restore_data a0 t1
>> + fpu_restore_cc a0 t1 t2
>> + fpu_restore_csr a0 t1
>> + jirl zero, ra, 0
>> +SYM_FUNC_END(kvm_restore_lsx)
>> +
>> +SYM_FUNC_START(kvm_restore_lsx_upper)
>> + lsx_restore_all_upper a0 t0 t1
>> +
>> + jirl zero, ra, 0
>> +SYM_FUNC_END(kvm_restore_lsx_upper)
>> +#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 a1e35d6554..7da4e230e8 100644
>> --- a/arch/loongarch/kvm/trace.h
>> +++ b/arch/loongarch/kvm/trace.h
>> @@ -102,6 +102,7 @@ TRACE_EVENT(kvm_exit_gspr,
>> #define KVM_TRACE_AUX_DISCARD 4
>> #define KVM_TRACE_AUX_FPU 1
>> +#define KVM_TRACE_AUX_LSX 2
>> #define kvm_trace_symbol_aux_op \
>> { KVM_TRACE_AUX_SAVE, "save" }, \
>> @@ -111,7 +112,8 @@ TRACE_EVENT(kvm_exit_gspr,
>> { KVM_TRACE_AUX_DISCARD, "discard" }
>> #define kvm_trace_symbol_aux_state \
>> - { KVM_TRACE_AUX_FPU, "FPU" }
>> + { KVM_TRACE_AUX_FPU, "FPU" }, \
>> + { KVM_TRACE_AUX_LSX, "LSX" }
>> 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 73d0c2b9c1..f0bb583353 100644
>> --- a/arch/loongarch/kvm/vcpu.c
>> +++ b/arch/loongarch/kvm/vcpu.c
>> @@ -378,9 +378,13 @@ static int kvm_set_one_reg(struct kvm_vcpu *vcpu,
>> break;
>> case KVM_REG_LOONGARCH_CPUCFG:
>> id = KVM_GET_IOC_CPUCFG_IDX(reg->id);
>> - if (id >= 0 && id < KVM_MAX_CPUCFG_REGS)
>> + if (id >= 0 && id < KVM_MAX_CPUCFG_REGS) {
>> vcpu->arch.cpucfg[id] = (u32)v;
>> - else
>> + if (id == 2 && v & CPUCFG2_LSX && !cpu_has_lsx) {
> Hi Tianrui,
>
> Can you add some annotations about these piece of codes? so that
> people can understand easily.
>
> And do we need interface to get host capabilities to user application?
> Such as QEMU first gets supported capabilities from kvm and then sets
> the required ones.
>
> Regards
> Bibo Mao
Thanks, I will add annotations for this and I think it is better to add
the checking LSX,LASX capabilities interfaces for user space and I will
supplement it later.
Thanks
Tianrui Zhao
>> + vcpu->arch.cpucfg[id] &= ~CPUCFG2_LSX;
>> + ret = -EINVAL;
>> + }
>> + } else
>> ret = -EINVAL;
>> break;
>> case KVM_REG_LOONGARCH_KVM:
>> @@ -561,12 +565,49 @@ void kvm_own_fpu(struct kvm_vcpu *vcpu)
>> preempt_enable();
>> }
>> +#ifdef CONFIG_CPU_HAS_LSX
>> +/* Enable LSX for guest and restore context */
>> +void kvm_own_lsx(struct kvm_vcpu *vcpu)
>> +{
>> + preempt_disable();
>> +
>> + /* Enable LSX for guest */
>> + set_csr_euen(CSR_EUEN_LSXEN | CSR_EUEN_FPEN);
>> + switch (vcpu->arch.aux_inuse & KVM_LARCH_FPU) {
>> + case KVM_LARCH_FPU:
>> + /*
>> + * Guest FPU state already loaded,
>> + * only restore upper LSX state
>> + */
>> + kvm_restore_lsx_upper(&vcpu->arch.fpu);
>> + break;
>> + default:
>> + /* Neither FP or LSX already active,
>> + * restore full LSX state
>> + */
>> + kvm_restore_lsx(&vcpu->arch.fpu);
>> + break;
>> + }
>> +
>> + trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LSX);
>> + vcpu->arch.aux_inuse |= 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_FPU) {
>> + 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);
>> +
>> + /* Disable LSX & FPU */
>> + clear_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN);
>> + } else if (vcpu->arch.aux_inuse & KVM_LARCH_FPU) {
>> kvm_save_fpu(&vcpu->arch.fpu);
>> vcpu->arch.aux_inuse &= ~KVM_LARCH_FPU;
>> trace_kvm_aux(vcpu, KVM_TRACE_AUX_SAVE, KVM_TRACE_AUX_FPU);
>>
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