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Date: Mon, 1 Jul 2024 18:26:57 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: maobibo <maobibo@...ngson.cn>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>, kvm@...r.kernel.org,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/3] LoongArch: KVM: Add LBT feature detection function
On Mon, Jul 1, 2024 at 9:27 AM maobibo <maobibo@...ngson.cn> wrote:
>
>
> Huacai,
>
> On 2024/6/30 上午10:07, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Wed, Jun 26, 2024 at 2:32 PM Bibo Mao <maobibo@...ngson.cn> wrote:
> >>
> >> Two kinds of LBT feature detection are added here, one is VCPU
> >> feature, the other is VM feature. VCPU feature dection can only
> >> work with VCPU thread itself, and requires VCPU thread is created
> >> already. So LBT feature detection for VM is added also, it can
> >> be done even if VM is not created, and also can be done by any
> >> thread besides VCPU threads.
> >>
> >> Loongson Binary Translation (LBT) feature is defined in register
> >> cpucfg2. Here LBT capability detection for VCPU is added.
> >>
> >> Here ioctl command KVM_HAS_DEVICE_ATTR is added for VM, and macro
> >> KVM_LOONGARCH_VM_FEAT_CTRL is added to check supported feature. And
> >> three sub-features relative with LBT are added as following:
> >> KVM_LOONGARCH_VM_FEAT_X86BT
> >> KVM_LOONGARCH_VM_FEAT_ARMBT
> >> KVM_LOONGARCH_VM_FEAT_MIPSBT
> >>
> >> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> >> ---
> >> arch/loongarch/include/uapi/asm/kvm.h | 6 ++++
> >> arch/loongarch/kvm/vcpu.c | 6 ++++
> >> arch/loongarch/kvm/vm.c | 44 ++++++++++++++++++++++++++-
> >> 3 files changed, 55 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
> >> index ddc5cab0ffd0..c40f7d9ffe13 100644
> >> --- a/arch/loongarch/include/uapi/asm/kvm.h
> >> +++ b/arch/loongarch/include/uapi/asm/kvm.h
> >> @@ -82,6 +82,12 @@ struct kvm_fpu {
> >> #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)
> >>
> >> +/* Device Control API on vm fd */
> >> +#define KVM_LOONGARCH_VM_FEAT_CTRL 0
> >> +#define KVM_LOONGARCH_VM_FEAT_X86BT 0
> >> +#define KVM_LOONGARCH_VM_FEAT_ARMBT 1
> >> +#define KVM_LOONGARCH_VM_FEAT_MIPSBT 2
> >> +
> >> /* Device Control API on vcpu fd */
> >> #define KVM_LOONGARCH_VCPU_CPUCFG 0
> >> #define KVM_LOONGARCH_VCPU_PVTIME_CTRL 1
> > If you insist that LBT should be a vm feature, then I suggest the
> > above two also be vm features. Though this is an UAPI change, but
> > CPUCFG is upstream in 6.10-rc1 and 6.10-final hasn't been released. We
> > have a chance to change it now.
>
> KVM_LOONGARCH_VCPU_PVTIME_CTRL need be attr percpu since every vcpu
> has is own different gpa address.
Then leave this as a vm feature.
>
> For KVM_LOONGARCH_VCPU_CPUCFG attr, it will not changed. We cannot break
> the API even if it is 6.10-rc1, VMM has already used this. Else there is
> uapi breaking now, still will be in future if we cannot control this.
UAPI changing before the first release is allowed, which means, we can
change this before the 6.10-final, but cannot change it after
6.10-final.
>
> How about adding new extra features capability for VM such as?
> +#define KVM_LOONGARCH_VM_FEAT_LSX 3
> +#define KVM_LOONGARCH_VM_FEAT_LASX 4
They should be similar as LBT, if LBT is vcpu feature, they should
also be vcpu features; if LBT is vm feature, they should also be vm
features.
Huacai
>
> Regards
> Bibo Mao
> >
> > Huacai
> >
> >> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> >> index 233d28d0e928..9734b4d8db05 100644
> >> --- a/arch/loongarch/kvm/vcpu.c
> >> +++ b/arch/loongarch/kvm/vcpu.c
> >> @@ -565,6 +565,12 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
> >> *v |= CPUCFG2_LSX;
> >> if (cpu_has_lasx)
> >> *v |= CPUCFG2_LASX;
> >> + if (cpu_has_lbt_x86)
> >> + *v |= CPUCFG2_X86BT;
> >> + if (cpu_has_lbt_arm)
> >> + *v |= CPUCFG2_ARMBT;
> >> + if (cpu_has_lbt_mips)
> >> + *v |= CPUCFG2_MIPSBT;
> >>
> >> return 0;
> >> case LOONGARCH_CPUCFG3:
> >> diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
> >> index 6b2e4f66ad26..09e05108c68b 100644
> >> --- a/arch/loongarch/kvm/vm.c
> >> +++ b/arch/loongarch/kvm/vm.c
> >> @@ -99,7 +99,49 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >> return r;
> >> }
> >>
> >> +static int kvm_vm_feature_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
> >> +{
> >> + switch (attr->attr) {
> >> + case KVM_LOONGARCH_VM_FEAT_X86BT:
> >> + if (cpu_has_lbt_x86)
> >> + return 0;
> >> + return -ENXIO;
> >> + case KVM_LOONGARCH_VM_FEAT_ARMBT:
> >> + if (cpu_has_lbt_arm)
> >> + return 0;
> >> + return -ENXIO;
> >> + case KVM_LOONGARCH_VM_FEAT_MIPSBT:
> >> + if (cpu_has_lbt_mips)
> >> + return 0;
> >> + return -ENXIO;
> >> + default:
> >> + return -ENXIO;
> >> + }
> >> +}
> >> +
> >> +static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
> >> +{
> >> + switch (attr->group) {
> >> + case KVM_LOONGARCH_VM_FEAT_CTRL:
> >> + return kvm_vm_feature_has_attr(kvm, attr);
> >> + default:
> >> + return -ENXIO;
> >> + }
> >> +}
> >> +
> >> int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> >> {
> >> - return -ENOIOCTLCMD;
> >> + struct kvm *kvm = filp->private_data;
> >> + void __user *argp = (void __user *)arg;
> >> + struct kvm_device_attr attr;
> >> +
> >> + switch (ioctl) {
> >> + case KVM_HAS_DEVICE_ATTR:
> >> + if (copy_from_user(&attr, argp, sizeof(attr)))
> >> + return -EFAULT;
> >> +
> >> + return kvm_vm_has_attr(kvm, &attr);
> >> + default:
> >> + return -EINVAL;
> >> + }
> >> }
> >> --
> >> 2.39.3
> >>
>
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