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Message-ID: <5375FFB8.90504@suse.de>
Date: Fri, 16 May 2014 14:08:24 +0200
From: Alexander Graf <agraf@...e.de>
To: Michael Mueller <mimu@...ux.vnet.ibm.com>, qemu-devel@...gnu.org,
kvm@...r.kernel.org, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org
CC: Cornelia Huck <cornelia.huck@...ibm.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Gleb Natapov <gleb@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Richard Henderson <rth@...ddle.net>,
Andreas Faerber <afaerber@...e.de>,
"Jason J. Herne" <jjherne@...ux.vnet.ibm.com>
Subject: Re: [PATCH v1 RFC 6/6] KVM: s390: add cpu model support
On 13.05.14 16:58, Michael Mueller wrote:
> This patch enables cpu model support in kvm/s390 via the vm attribute
> interface.
>
> During KVM initialization, the host properties cpuid, IBC value and the
> facility list are stored in the architecture specific cpu model structure.
>
> During vcpu setup, these properties are taken to initialize the related SIE
> state. This mechanism allows to adjust the properties from user space and thus
> to implement different selectable cpu models.
>
> This patch uses the IBC functionality to block instructions that have not
> been implemented at the requested CPU type and GA level compared to the
> full host capability.
>
> Userspace has to initialize the cpu model before vcpu creation. A cpu model
> change of running vcpus is currently not possible.
Why is this VM global? It usually fits a lot better modeling wise when
CPU types are vcpu properties.
>
> Signed-off-by: Michael Mueller <mimu@...ux.vnet.ibm.com>
> ---
> arch/s390/include/asm/kvm_host.h | 4 +-
> arch/s390/include/uapi/asm/kvm.h | 23 ++++++
> arch/s390/kvm/kvm-s390.c | 146 ++++++++++++++++++++++++++++++++++++++-
> arch/s390/kvm/kvm-s390.h | 1 +
> 4 files changed, 172 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index b4751ba..6b826cb 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -84,7 +84,8 @@ struct kvm_s390_sie_block {
> atomic_t cpuflags; /* 0x0000 */
> __u32 : 1; /* 0x0004 */
> __u32 prefix : 18;
> - __u32 : 13;
> + __u32 : 1;
> + __u32 ibc : 12;
> __u8 reserved08[4]; /* 0x0008 */
> #define PROG_IN_SIE (1<<0)
> __u32 prog0c; /* 0x000c */
> @@ -418,6 +419,7 @@ struct kvm_s390_cpu_model {
> unsigned long *sie_fac;
> struct cpuid cpu_id;
> unsigned long *fac_list;
> + unsigned short ibc;
> };
>
> struct kvm_arch{
> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
> index 313100a..82ef1b5 100644
> --- a/arch/s390/include/uapi/asm/kvm.h
> +++ b/arch/s390/include/uapi/asm/kvm.h
> @@ -58,12 +58,35 @@ struct kvm_s390_io_adapter_req {
>
> /* kvm attr_group on vm fd */
> #define KVM_S390_VM_MEM_CTRL 0
> +#define KVM_S390_VM_CPU_MODEL 1
>
> /* kvm attributes for mem_ctrl */
> #define KVM_S390_VM_MEM_ENABLE_CMMA 0
> #define KVM_S390_VM_MEM_CLR_CMMA 1
> #define KVM_S390_VM_MEM_CLR_PAGES 2
>
> +/* kvm attributes for cpu_model */
> +
> +/* the s390 processor related attributes are r/w */
> +#define KVM_S390_VM_CPU_PROCESSOR 0
> +struct kvm_s390_vm_cpu_processor {
> + __u64 cpuid;
> + __u16 ibc;
> + __u8 pad[6];
> + __u64 fac_list[256];
> +};
> +
> +/* the machine related attributes are read only */
> +#define KVM_S390_VM_CPU_MACHINE 1
> +struct kvm_s390_vm_cpu_machine {
> + __u64 cpuid;
> + __u32 ibc_range;
> + __u8 pad[4];
> + __u64 fac_mask[256];
> + __u64 hard_fac_list[256];
> + __u64 soft_fac_list[256];
> +};
> +
> /* for KVM_GET_REGS and KVM_SET_REGS */
> struct kvm_regs {
> /* general purpose regs for s390 */
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index a53652f..9965d8b 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -369,6 +369,110 @@ static int kvm_s390_mem_control(struct kvm *kvm, struct kvm_device_attr *attr)
> return ret;
> }
>
> +static int kvm_s390_set_processor(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> + struct kvm_s390_vm_cpu_processor *proc;
> +
> + if (atomic_read(&kvm->online_vcpus))
> + return -EBUSY;
> +
> + proc = kzalloc(sizeof(*proc), GFP_KERNEL);
> + if (!proc)
> + return -ENOMEM;
> +
> + if (copy_from_user(proc, (void __user *)attr->addr,
> + sizeof(*proc))) {
> + kfree(proc);
> + return -EFAULT;
> + }
> +
> + mutex_lock(&kvm->lock);
> + memcpy(&kvm->arch.model.cpu_id, &proc->cpuid,
> + sizeof(struct cpuid));
> + kvm->arch.model.ibc = proc->ibc;
> + kvm_s390_apply_fac_list_mask((long unsigned *)proc->fac_list);
> + memcpy(kvm->arch.model.fac_list, proc->fac_list,
> + S390_ARCH_FAC_LIST_SIZE_BYTE);
> + mutex_unlock(&kvm->lock);
> + kfree(proc);
> +
> + return 0;
> +}
> +
> +static int kvm_s390_set_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> + int ret = -ENXIO;
> +
> + switch (attr->attr) {
> + case KVM_S390_VM_CPU_PROCESSOR:
> + ret = kvm_s390_set_processor(kvm, attr);
> + break;
> + }
> + return ret;
> +}
> +
> +static int kvm_s390_get_processor(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> + struct kvm_s390_vm_cpu_processor *proc;
> + int rc = 0;
> +
> + proc = kzalloc(sizeof(*proc), GFP_KERNEL);
> + if (!proc) {
> + rc = -ENOMEM;
> + goto out;
> + }
> + memcpy(&proc->cpuid, &kvm->arch.model.cpu_id, sizeof(struct cpuid));
> + proc->ibc = kvm->arch.model.ibc;
> + memcpy(&proc->fac_list, kvm->arch.model.fac_list,
> + S390_ARCH_FAC_LIST_SIZE_BYTE);
> + if (copy_to_user((void __user *)attr->addr, proc, sizeof(*proc)))
> + rc = -EFAULT;
> + kfree(proc);
> +out:
> + return rc;
> +}
> +
> +static int kvm_s390_get_machine(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> + struct kvm_s390_vm_cpu_machine *mach;
> + int rc = 0;
> +
> + mach = kzalloc(sizeof(*mach), GFP_KERNEL);
> + if (!mach) {
> + rc = -ENOMEM;
> + goto out;
> + }
> + get_cpu_id((struct cpuid *) &mach->cpuid);
> + mach->ibc_range = kvm_s390_lowest_ibc() << 16;
> + mach->ibc_range |= kvm_s390_latest_ibc();
> + memcpy(&mach->fac_mask, kvm_s390_fac_list_mask,
> + kvm_s390_fac_list_mask_size() * sizeof(u64));
> + kvm_s390_get_hard_fac_list((long unsigned int *) &mach->hard_fac_list,
> + S390_ARCH_FAC_LIST_SIZE_U64);
> + kvm_s390_get_soft_fac_list((long unsigned int *) &mach->soft_fac_list,
> + S390_ARCH_FAC_LIST_SIZE_U64);
I really have a hard time grasping what hard and soft means.
Also, if user space wants to make sure that its feature list is actually
workable on the host kernel, it needs to set and get the features again
and then compare that with the ones it set? That's different from x86's
cpuid implementation but probably workable.
I also don't quite grasp what the story behind IBC is. Do you actually
block instructions? Where do you match instructions that have to get
blocked with instructions that user space wants to see exposed?
Alex
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