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Date: Thu, 16 Nov 2023 15:15:00 +0800
From: WANG Xuerui <kernel@...0n.name>
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>,
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 1/2] LoongArch: KVM: Add lsx support
On 11/15/23 17:19, Tianrui Zhao wrote:
> This patch adds LSX support for LoongArch KVM. The LSX means
> LoongArch 128-bits vector instruction.
Maybe we don't need to explain what "LSX" is; people working on
LoongArch kernel should already know this through the kernel docs and
the various occurrences in the code.
> 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.
>
One more extra line that should get removed.
> 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
"jr ra" for consistency (e.g. with the function immediately above);
similarly for other such usages.
> +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) {
> + 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);
--
WANG "xen0n" Xuerui
Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
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