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Message-ID: <5b568152-7912-c613-588e-7b2bf1491ee5@loongson.cn>
Date: Tue, 9 Jul 2024 17:22:56 +0800
From: maobibo <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>
Cc: kvm@...r.kernel.org, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] LoongArch: KVM: Implement feature passing from user
space
Gently ping.
On 2024/6/11 下午8:36, Bibo Mao wrote:
> Currently features defined in cpucfg CPUCFG_KVM_FEATURE come from
> kvm kernel mode only. However KVM is not aware of user-space VMM
> features which makes it hard to employ optimizations. Here interface
> is added to update register CPUCFG_KVM_FEATURE from user space,
> only bit 24 - 31 is valid, so that VM can detect features implemented
> in user-space VMM.
>
> A new feature bit KVM_LOONGARCH_VCPU_FEAT_VIRT_EXTIOI is added which
> can be set from user space. This feature indicates that the virt EXTIOI
> can route interrupts to 256 vCPUs, rather than 4 vCPUs like with real HW.
>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
> v1 ... v2:
> 1. Update changelog suggested by WangXuerui.
> 2. Fix typo issue in function kvm_loongarch_cpucfg_set_attr(), usr_features
> should be assigned directly, also suggested by WangXueRui.
> ---
> arch/loongarch/include/asm/kvm_host.h | 4 +++
> arch/loongarch/include/asm/loongarch.h | 5 ++++
> arch/loongarch/include/uapi/asm/kvm.h | 2 ++
> arch/loongarch/kvm/exit.c | 1 +
> arch/loongarch/kvm/vcpu.c | 36 +++++++++++++++++++++++---
> 5 files changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index 88023ab59486..8fa50d757247 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -135,6 +135,9 @@ enum emulation_result {
> #define KVM_LARCH_HWCSR_USABLE (0x1 << 4)
> #define KVM_LARCH_LBT (0x1 << 5)
>
> +#define KVM_LOONGARCH_USR_FEAT_MASK \
> + BIT(KVM_LOONGARCH_VCPU_FEAT_VIRT_EXTIOI)
> +
> struct kvm_vcpu_arch {
> /*
> * Switch pointer-to-function type to unsigned long
> @@ -210,6 +213,7 @@ struct kvm_vcpu_arch {
> u64 last_steal;
> struct gfn_to_hva_cache cache;
> } st;
> + unsigned int usr_features;
> };
>
> static inline unsigned long readl_sw_gcsr(struct loongarch_csrs *csr, int reg)
> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> index 7a4633ef284b..4d9837512c19 100644
> --- a/arch/loongarch/include/asm/loongarch.h
> +++ b/arch/loongarch/include/asm/loongarch.h
> @@ -167,9 +167,14 @@
>
> #define CPUCFG_KVM_SIG (CPUCFG_KVM_BASE + 0)
> #define KVM_SIGNATURE "KVM\0"
> +/*
> + * BIT 24 - 31 is features configurable by user space vmm
> + */
> #define CPUCFG_KVM_FEATURE (CPUCFG_KVM_BASE + 4)
> #define KVM_FEATURE_IPI BIT(1)
> #define KVM_FEATURE_STEAL_TIME BIT(2)
> +/* With VIRT_EXTIOI feature, interrupt can route to 256 VCPUs */
> +#define KVM_FEATURE_VIRT_EXTIOI BIT(24)
>
> #ifndef __ASSEMBLY__
>
> diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
> index ed12e509815c..dd141259de48 100644
> --- a/arch/loongarch/include/uapi/asm/kvm.h
> +++ b/arch/loongarch/include/uapi/asm/kvm.h
> @@ -99,6 +99,8 @@ struct kvm_fpu {
>
> /* Device Control API on vcpu fd */
> #define KVM_LOONGARCH_VCPU_CPUCFG 0
> +/* For CPUCFG_KVM_FEATURE register */
> +#define KVM_LOONGARCH_VCPU_FEAT_VIRT_EXTIOI 24
> #define KVM_LOONGARCH_VCPU_PVTIME_CTRL 1
> #define KVM_LOONGARCH_VCPU_PVTIME_GPA 0
>
> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> index e1bd81d27fd8..ab2dcc76784a 100644
> --- a/arch/loongarch/kvm/exit.c
> +++ b/arch/loongarch/kvm/exit.c
> @@ -53,6 +53,7 @@ static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
> ret = KVM_FEATURE_IPI;
> if (sched_info_on())
> ret |= KVM_FEATURE_STEAL_TIME;
> + ret |= vcpu->arch.usr_features;
> vcpu->arch.gprs[rd] = ret;
> break;
> default:
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index 3783151fde32..4a06a9e96e4e 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -832,6 +832,8 @@ static int kvm_loongarch_cpucfg_has_attr(struct kvm_vcpu *vcpu,
> switch (attr->attr) {
> case 2:
> return 0;
> + case CPUCFG_KVM_FEATURE:
> + return 0;
> default:
> return -ENXIO;
> }
> @@ -865,9 +867,18 @@ static int kvm_loongarch_get_cpucfg_attr(struct kvm_vcpu *vcpu,
> uint64_t val;
> uint64_t __user *uaddr = (uint64_t __user *)attr->addr;
>
> - ret = _kvm_get_cpucfg_mask(attr->attr, &val);
> - if (ret)
> - return ret;
> + switch (attr->attr) {
> + case 0 ... (KVM_MAX_CPUCFG_REGS - 1):
> + ret = _kvm_get_cpucfg_mask(attr->attr, &val);
> + if (ret)
> + return ret;
> + break;
> + case CPUCFG_KVM_FEATURE:
> + val = vcpu->arch.usr_features & KVM_LOONGARCH_USR_FEAT_MASK;
> + break;
> + default:
> + return -ENXIO;
> + }
>
> put_user(val, uaddr);
>
> @@ -896,7 +907,24 @@ static int kvm_loongarch_vcpu_get_attr(struct kvm_vcpu *vcpu,
> static int kvm_loongarch_cpucfg_set_attr(struct kvm_vcpu *vcpu,
> struct kvm_device_attr *attr)
> {
> - return -ENXIO;
> + u64 __user *user = (u64 __user *)attr->addr;
> + u64 val, valid_flags;
> +
> + switch (attr->attr) {
> + case CPUCFG_KVM_FEATURE:
> + if (get_user(val, user))
> + return -EFAULT;
> +
> + valid_flags = KVM_LOONGARCH_USR_FEAT_MASK;
> + if (val & ~valid_flags)
> + return -EINVAL;
> +
> + vcpu->arch.usr_features = val;
> + return 0;
> +
> + default:
> + return -ENXIO;
> + }
> }
>
> static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
>
> base-commit: 2df0193e62cf887f373995fb8a91068562784adc
>
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