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Message-ID: <4757aae2-83f4-6e20-8fc2-d2ad39126008@loongson.cn>
Date: Tue, 5 Dec 2023 21:25:31 +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 1/2] LoongArch: KVM: Add LSX support
On 2023/12/1 下午4:46, Tianrui Zhao wrote:
> This patch adds LSX support for LoongArch KVM.
> 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 | 12 ++-
> arch/loongarch/include/asm/kvm_vcpu.h | 12 +++
> arch/loongarch/include/uapi/asm/kvm.h | 19 +++--
> arch/loongarch/kvm/exit.c | 18 +++++
> arch/loongarch/kvm/switch.S | 21 +++++
> arch/loongarch/kvm/trace.h | 4 +-
> arch/loongarch/kvm/vcpu.c | 109 ++++++++++++++++++++++++--
> 7 files changed, 179 insertions(+), 16 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index 11328700d4f..a53b47093f4 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -21,8 +21,10 @@
> #include <asm/loongarch.h>
>
> /* Loongarch KVM register ids */
> -#define KVM_GET_IOC_CSR_IDX(id) ((id & KVM_CSR_IDX_MASK) >> LOONGARCH_REG_SHIFT)
> -#define KVM_GET_IOC_CPUCFG_IDX(id) ((id & KVM_CPUCFG_IDX_MASK) >> LOONGARCH_REG_SHIFT)
> +#define KVM_GET_IOC_CSR_IDX(id) ((id & KVM_CSR_IDX_MASK) >> LOONGARCH_REG_SHIFT)
> +#define KVM_GET_IOC_CPUCFG_IDX(id) ((id & KVM_CPUCFG_IDX_MASK) >> LOONGARCH_REG_SHIFT)
> +#define KVM_GET_IOC_CPUCFG_SUPPORTED_IDX(id) ((id & KVM_CPUCFG_SUPPORTED_IDX_MASK) >> \
> + LOONGARCH_REG_SHIFT)
>
> #define KVM_MAX_VCPUS 256
> #define KVM_MAX_CPUCFG_REGS 21
> @@ -94,6 +96,7 @@ 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 +178,11 @@ 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 553cfa2b2b1..c629771e122 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/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
> index c6ad2ee6106..cfea150be8e 100644
> --- a/arch/loongarch/include/uapi/asm/kvm.h
> +++ b/arch/loongarch/include/uapi/asm/kvm.h
> @@ -59,14 +59,16 @@ struct kvm_fpu {
> * have its own identifier in bits[31..16].
> */
>
> -#define KVM_REG_LOONGARCH_GPR (KVM_REG_LOONGARCH | 0x00000ULL)
> -#define KVM_REG_LOONGARCH_CSR (KVM_REG_LOONGARCH | 0x10000ULL)
> -#define KVM_REG_LOONGARCH_KVM (KVM_REG_LOONGARCH | 0x20000ULL)
> -#define KVM_REG_LOONGARCH_FPSIMD (KVM_REG_LOONGARCH | 0x30000ULL)
> -#define KVM_REG_LOONGARCH_CPUCFG (KVM_REG_LOONGARCH | 0x40000ULL)
> -#define KVM_REG_LOONGARCH_MASK (KVM_REG_LOONGARCH | 0x70000ULL)
> -#define KVM_CSR_IDX_MASK 0x7fff
> -#define KVM_CPUCFG_IDX_MASK 0x7fff
> +#define KVM_REG_LOONGARCH_GPR (KVM_REG_LOONGARCH | 0x00000ULL)
> +#define KVM_REG_LOONGARCH_CSR (KVM_REG_LOONGARCH | 0x10000ULL)
> +#define KVM_REG_LOONGARCH_KVM (KVM_REG_LOONGARCH | 0x20000ULL)
> +#define KVM_REG_LOONGARCH_FPSIMD (KVM_REG_LOONGARCH | 0x30000ULL)
> +#define KVM_REG_LOONGARCH_CPUCFG (KVM_REG_LOONGARCH | 0x40000ULL)
> +#define KVM_REG_LOONGARCH_CPUCFG_SUPPORTED (KVM_REG_LOONGARCH | 0x50000ULL)
> +#define KVM_REG_LOONGARCH_MASK (KVM_REG_LOONGARCH | 0x70000ULL)
> +#define KVM_CSR_IDX_MASK 0x7fff
> +#define KVM_CPUCFG_IDX_MASK 0x7fff
> +#define KVM_CPUCFG_SUPPORTED_IDX_MASK 0x7fff
>
> /*
> * KVM_REG_LOONGARCH_KVM - KVM specific control registers.
> @@ -79,6 +81,7 @@ struct kvm_fpu {
> #define LOONGARCH_REG_64(TYPE, REG) (TYPE | KVM_REG_SIZE_U64 | (REG << LOONGARCH_REG_SHIFT))
> #define KVM_IOC_CSRID(REG) LOONGARCH_REG_64(KVM_REG_LOONGARCH_CSR, REG)
> #define KVM_IOC_CPUCFG(REG) LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG, REG)
> +#define KVM_IOC_CPUCFG_SUPPORTED(REG) LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG_SUPPORTED, REG)
>
> struct kvm_debug_exit_arch {
> };
> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> index ce8de3fa472..1b1c58ccc83 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 0ed9040307b..6c48f7d1ca5 100644
> --- a/arch/loongarch/kvm/switch.S
> +++ b/arch/loongarch/kvm/switch.S
> @@ -245,6 +245,27 @@ 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
> + jr ra
> +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 t2
> + jr ra
> +SYM_FUNC_END(kvm_restore_lsx)
> +
> +SYM_FUNC_START(kvm_restore_lsx_upper)
> + lsx_restore_all_upper a0 t0 t1
> + jr ra
> +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 a1e35d65541..7da4e230e89 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 73d0c2b9c1a..4820c95091f 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -309,6 +309,34 @@ static int _kvm_setcsr(struct kvm_vcpu *vcpu, unsigned int id, u64 val)
> return ret;
> }
>
> +static int kvm_get_cpucfg_supported(int id, u64 *v)
> +{
> + int ret = 0;
> +
> + if (id < 0 && id >= KVM_MAX_CPUCFG_REGS)
> + return -EINVAL;
> +
> + switch (id) {
> + /* Only CPUCFG2 checking are supported, we will add all CPUCFGs checking later. */
> + case 2:
> + /* return CPUCFG2 features which have been supported by KVM */
> + *v = CPUCFG2_FP | CPUCFG2_FPSP | CPUCFG2_FPDP |
> + CPUCFG2_FPVERS | CPUCFG2_LLFTP | CPUCFG2_LLFTPREV |
> + CPUCFG2_LAM;
> + /*
> + * if LSX is supported by CPU, it is also supported by KVM,
> + * as we implement it.
> + */
> + if (cpu_has_lsx)
> + *v |= CPUCFG2_LSX;
> + break;
> + default:
> + ret = -EINVAL;
> + break;
> + }
> + return ret;
> +}
> +
> static int kvm_get_one_reg(struct kvm_vcpu *vcpu,
> const struct kvm_one_reg *reg, u64 *v)
> {
> @@ -327,6 +355,10 @@ static int kvm_get_one_reg(struct kvm_vcpu *vcpu,
> else
> ret = -EINVAL;
> break;
> + case KVM_REG_LOONGARCH_CPUCFG_SUPPORTED:
> + id = KVM_GET_IOC_CPUCFG_SUPPORTED_IDX(reg->id);
> + ret = kvm_get_cpucfg_supported(id, v);
> + break;
To be frankly, KVM_REG_LOONGARCH_CPUCFG_SUPPORTED is a little strange, I
prefer to DEVICE_ATTR for vcpu such as KVM_GET_DEVICE_ATTR, since it
exists already and also pv stealtime can be used by this ioctl command.
> case KVM_REG_LOONGARCH_KVM:
> switch (reg->id) {
> case KVM_REG_LOONGARCH_COUNTER:
> @@ -365,6 +397,36 @@ static int kvm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> return ret;
> }
>
> +static int kvm_check_cpucfg(int id, u64 val)
> +{
> + u64 mask;
> + int ret = 0;
> +
> + if (id < 0 && id >= KVM_MAX_CPUCFG_REGS)
> + return -EINVAL;
> +
> + switch (id) {
> + case 2:
> + ret = kvm_get_cpucfg_supported(id, &mask);
> + /*
> + * CPUCFG2 features checking, if features are not supported, return false.
> + * Features version checking, if feature enabled but without version bits
> + * or feature disabled but along with version bits, return false.
> + */
> + if (!ret) {
> + if ((val & ~mask) ||
> + (!!(val & CPUCFG2_FP) != !!(val & CPUCFG2_FPVERS)) ||
> + (!!(val & CPUCFG2_LLFTP) != !!(val & CPUCFG2_LLFTPREV)))
> + ret = -EINVAL;
What is the logic for the above sentences? Is there special logic about
FPVERS?
How about such lines like this?
/*
* Reserved bit for future usage can not be set
* FP and LLFTP must be enabled
*/
if ((val & ~mask) || !(val & CPUCFG2_LLFTP) || !(val & CPUCFG2_FP))
Regards
Bibo Mao
> + } else
> + ret = -EINVAL;
> + break;
> + default:
> + break;
> + }
> + return ret;
> +}
> +
> static int kvm_set_one_reg(struct kvm_vcpu *vcpu,
> const struct kvm_one_reg *reg, u64 v)
> {
> @@ -378,10 +440,10 @@ 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)
> - vcpu->arch.cpucfg[id] = (u32)v;
> - else
> - ret = -EINVAL;
> + ret = kvm_check_cpucfg(id, v);
> + if (ret)
> + break;
> + vcpu->arch.cpucfg[id] = (u32)v;
> break;
> case KVM_REG_LOONGARCH_KVM:
> switch (reg->id) {
> @@ -561,12 +623,49 @@ 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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