Re: [Xen-devel] [PATCH v2] x86: generic MSRs save/restore

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.12.13 at 09:39, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> Jan Beulich wrote:
>>>>> On 16.12.13 at 04:01, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
>>> Jan Beulich wrote:
>>>> This patch introduces a generic MSRs save/restore mechanism, so that
>>>> in the future new MSRs save/restore could be added w/ smaller change
>>>> than the full blown addition of a new save/restore type.
>>>> 
>>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>> 
>>>> --- a/xen/arch/x86/hvm/hvm.c
>>>> +++ b/xen/arch/x86/hvm/hvm.c
>>>> @@ -1127,10 +1127,117 @@ static int hvm_load_cpu_xsave_states(str  
>>>>  return 0; }
>>>> 
>>>> -/* We need variable length data chunk for xsave area, hence
>>>> customized 
>>>> - * declaration other than HVM_REGISTER_SAVE_RESTORE.
>>>> +#define HVM_CPU_MSR_SIZE(cnt) offsetof(struct hvm_msr, msr[cnt])
>>>> +static unsigned int __read_mostly msr_count_max;
>>>> +
>>>> +static int hvm_save_cpu_msrs(struct domain *d,
>>>> hvm_domain_context_t *h) +{ +    struct vcpu *v;
>>>> +
>>>> +    for_each_vcpu ( d, v )
>>>> +    {
>>>> +        struct hvm_msr *ctxt;
>>>> +        unsigned int i;
>>>> +
>>>> +        if ( _hvm_init_entry(h, CPU_MSR_CODE, v->vcpu_id,
>>>> +                             HVM_CPU_MSR_SIZE(msr_count_max)) ) + 
>>>> return 1; +        ctxt = (struct hvm_msr *)&h->data[h->cur]; +    
>>>> ctxt->count = 0; +
>>>> +        if ( hvm_funcs.save_msr )
>>>> +            hvm_funcs.save_msr(v, ctxt);
>>>> +
>>>> +        for ( i = 0; i < ctxt->count; ++i )
>>>> +            ctxt->msr[i]._rsvd = 0;
>>>> +
>>>> +        if ( ctxt->count )
>>>> +            h->cur += HVM_CPU_MSR_SIZE(ctxt->count); +        else
>>>> +            h->cur -= sizeof(struct hvm_save_descriptor); +    }
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int hvm_load_cpu_msrs(struct domain *d,
>>>> hvm_domain_context_t *h) +{ +    unsigned int i, vcpuid =
>>>> hvm_load_instance(h); +    struct vcpu *v; +    const struct
>>>> hvm_save_descriptor *desc; +    struct hvm_msr *ctxt;
>>>> +    int err = 0;
>>>> +
>>>> +    if ( vcpuid >= d->max_vcpus || (v = d->vcpu[vcpuid]) == NULL )
>>>> +    { +        dprintk(XENLOG_G_ERR, "HVM restore: dom%d has no
>>>> vcpu%u\n", +                d->domain_id, vcpuid);
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>> +    /* Customized checking for entry since our entry is of variable
>>>> length */ +    desc = (struct hvm_save_descriptor
>>>> *)&h->data[h->cur]; +    if ( sizeof (*desc) > h->size - h->cur)
>>>> +    {
>>>> +        printk(XENLOG_G_WARNING
>>>> +               "HVM%d.%d restore: not enough data left to read MSR
>>>> descriptor\n", +               d->domain_id, vcpuid); +       
>>>> return -ENODATA; +    }
>>>> +    if ( desc->length + sizeof (*desc) > h->size - h->cur) +    {
>>>> +        printk(XENLOG_G_WARNING
>>>> +               "HVM%d.%d restore: not enough data left to read %u
>>>> MSR bytes\n", +               d->domain_id, vcpuid, desc->length);
>>>> +        return -ENODATA; +    }
>>>> +    if ( desc->length < HVM_CPU_MSR_SIZE(1) )
>>>> +    {
>>>> +        printk(XENLOG_G_WARNING
>>>> +               "HVM%d.%d restore mismatch: MSR length %u < %zu\n",
>>>> +               d->domain_id, vcpuid, desc->length,
>>>> HVM_CPU_MSR_SIZE(1)); +        return -EINVAL;
>>>> +    }
>>>> +
>>>> +    h->cur += sizeof(*desc);
>>>> +    ctxt = (struct hvm_msr *)&h->data[h->cur];
>>>> +    h->cur += desc->length;
>>>> +
>>>> +    if ( desc->length != HVM_CPU_MSR_SIZE(ctxt->count) ) +    {
>>>> +        printk(XENLOG_G_WARNING
>>>> +               "HVM%d.%d restore mismatch: MSR length %u != %zu\n",
>>>> +               d->domain_id, vcpuid, desc->length,
>>>> +               HVM_CPU_MSR_SIZE(ctxt->count));
>>>> +        return -EOPNOTSUPP;
>>>> +    }
>>>> +
>>>> +    for ( i = 0; i < ctxt->count; ++i )
>>>> +        if ( ctxt->msr[i]._rsvd )
>>>> +            return -EOPNOTSUPP;
>>>> +    /* Checking finished */
>>>> +
>>>> +    if ( hvm_funcs.load_msr )
>>>> +        err = hvm_funcs.load_msr(v, ctxt);
>>>> +
>>>> +    for ( i = 0; !err && i < ctxt->count; ++i )
>>>> +    {
>>>> +        switch ( ctxt->msr[i].index )
>>>> +        {
>>>> +        default:
>>>> +            if ( !ctxt->msr[i]._rsvd )
>>>> +                err = -ENXIO;
>>>> +            break;
>>>> +        }
>>>> +    }
>>>> +
>>>> +    return err;
>>>> +}
>>>> +
>>>> +/* We need variable length data chunks for XSAVE area and MSRs,
>>>> hence + * a custom declaration rather than
>>>> HVM_REGISTER_SAVE_RESTORE.   */ -static int __init
>>>> __hvm_register_CPU_XSAVE_save_and_restore(void) +static int __init
>>>>      hvm_register_CPU_save_and_restore(void)  {
>>>>                          hvm_register_savevm(CPU_XSAVE_CODE,
>>>> "CPU_XSAVE", @@ -1139,9 +1246,22 @@ static int __init
>>>>                          __hvm_register_CPU_XSA
>>>>                              HVM_CPU_XSAVE_SIZE(xfeature_mask) +
>>>>                          sizeof(struct hvm_save_descriptor),
>>>> HVMSR_PER_VCPU); +
>>>> +    if ( hvm_funcs.init_msr )
>>>> +        msr_count_max += hvm_funcs.init_msr();
>>>> +
>>>> +    if ( msr_count_max )
>>>> +        hvm_register_savevm(CPU_MSR_CODE,
>>>> +                            "CPU_MSR",
>>>> +                            hvm_save_cpu_msrs,
>>>> +                            hvm_load_cpu_msrs,
>>>> +                            HVM_CPU_MSR_SIZE(msr_count_max) +
>>>> +                                sizeof(struct hvm_save_descriptor),
>>>> +                            HVMSR_PER_VCPU);
>>>> +
>>>>      return 0;
>>>>  }
>>>> -__initcall(__hvm_register_CPU_XSAVE_save_and_restore);
>>>> +__initcall(hvm_register_CPU_save_and_restore);
>>>> 
>>>>  int hvm_vcpu_initialise(struct vcpu *v)
>>>>  {
>>>> --- a/xen/include/asm-x86/hvm/hvm.h
>>>> +++ b/xen/include/asm-x86/hvm/hvm.h
>>>> @@ -109,6 +109,10 @@ struct hvm_function_table {
>>>>      void (*save_cpu_ctxt)(struct vcpu *v, struct hvm_hw_cpu *ctxt);
>>>>      int (*load_cpu_ctxt)(struct vcpu *v, struct hvm_hw_cpu *ctxt);
>>>> 
>>>> +    unsigned int (*init_msr)(void);
>>>> +    void (*save_msr)(struct vcpu *, struct hvm_msr *);
>>>> +    int (*load_msr)(struct vcpu *, struct hvm_msr *); +
>>>>      /* Examine specifics of the guest state. */
>>>>      unsigned int (*get_interrupt_shadow)(struct vcpu *v);
>>>>      void (*set_interrupt_shadow)(struct vcpu *v, unsigned int
>>>> intr_shadow); --- a/xen/include/public/arch-x86/hvm/save.h
>>>> +++ b/xen/include/public/arch-x86/hvm/save.h
>>>> @@ -592,9 +592,21 @@ struct hvm_tsc_adjust {
>>>> 
>>>>  DECLARE_HVM_SAVE_TYPE(TSC_ADJUST, 19, struct hvm_tsc_adjust);
>>>> 
>>>> +
>>>> +struct hvm_msr {
>>>> +    uint32_t count;
>>>> +    struct hvm_one_msr {
>>>> +        uint32_t index;
>>>> +        uint32_t _rsvd;
>>>> +        uint64_t val;
>>>> +    } msr[1 /* variable size */];
>>>> +};
>>>> +
>>>> +#define CPU_MSR_CODE  20
>>>> +
>>> 
>>> +DECLARE_HVM_SAVE_TYPE(CPU_MSR, CPU_MSR_CODE, struct hvm_msr);
>>> +msr dump patch at tools/misc/xen-hvmctx.c
>> 
>> Sorry, I don't follow what this is to mean. If that other patch of
>> yours needs adjustment, then this surely doesn't belong here.
>> 
> 
> OK, I will adjust tools side msr dump patch.
> 
> DECLARE_HVM_SAVE_TYPE(CPU_MSR, CPU_MSR_CODE, struct hvm_msr) is for msr dump 
> tools side patch, so if you don't add it here I can use a distinct patch to 
> add it.

The main thing is - this does _not_ belong in the public header, just
like the XSAVE one has no such declaration there.

Jan

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