Re: [Xen-devel] [PATCH 1/2] x86/hvm/viridian: keep APIC assist page mapped...

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: 15 March 2016 23:20
> To: Paul Durrant
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Andrew Cooper; Keir (Xen.org); Jan
> Beulich
> Subject: Re: [Xen-devel] [PATCH 1/2] x86/hvm/viridian: keep APIC assist
> page mapped...
> 
> On Tue, Mar 15, 2016 at 04:14:15PM +0000, Paul Durrant wrote:
> > ... for the lifetime of the domain.
> >
> > If Xen is to make use of the APIC assist enlightenment then a persistent
> > mapping needs to be kept, rather than the temporary one which is
> currently
> > used only to initialize the page content.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > Cc: Keir Fraser <keir@xxxxxxx>
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > ---
> >  xen/arch/x86/hvm/viridian.c        | 54 +++++++++++++++++++++++++++--
> ---------
> >  xen/include/asm-x86/hvm/viridian.h |  6 ++++-
> >  2 files changed, 43 insertions(+), 17 deletions(-)
> >
> > diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
> > index 6bd844b..c779290 100644
> > --- a/xen/arch/x86/hvm/viridian.c
> > +++ b/xen/arch/x86/hvm/viridian.c
> > @@ -163,7 +163,7 @@ static void dump_apic_assist(const struct vcpu *v)
> >  {
> >      const union viridian_apic_assist *aa;
> >
> > -    aa = &v->arch.hvm_vcpu.viridian.apic_assist;
> > +    aa = &v->arch.hvm_vcpu.viridian.apic_assist.msr;
> >
> >      printk(XENLOG_G_INFO "%pv: VIRIDIAN APIC_ASSIST: enabled: %x pfn:
> %lx\n",
> >             v, aa->fields.enabled, (unsigned long)aa->fields.pfn);
> > @@ -217,9 +217,9 @@ static void enable_hypercall_page(struct domain
> *d)
> >  static void initialize_apic_assist(struct vcpu *v)
> >  {
> >      struct domain *d = v->domain;
> > -    unsigned long gmfn = v->arch.hvm_vcpu.viridian.apic_assist.fields.pfn;
> > +    unsigned long gmfn = v-
> >arch.hvm_vcpu.viridian.apic_assist.msr.fields.pfn;
> >      struct page_info *page = get_page_from_gfn(d, gmfn, NULL,
> P2M_ALLOC);
> > -    uint8_t *p;
> > +    void *va;
> >
> >      /*
> >       * We don't yet make use of the APIC assist page but by setting
> > @@ -231,21 +231,40 @@ static void initialize_apic_assist(struct vcpu *v)
> >       * details of how Windows uses the page.
> >       */
> >
> > -    if ( !page || !get_page_type(page, PGT_writable_page) )
> > +    if ( !page )
> > +        return;
> > +
> > +    if ( !get_page_type(page, PGT_writable_page) )
> >      {
> > -        if ( page )
> > -            put_page(page);
> > -        gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
> > -                 page ? page_to_mfn(page) : INVALID_MFN);
> > +        put_page(page);
> 
> You don't want to report errors in case this goes south?
> 

Well, the guest should keep on running but without the enlightenment. You're 
right that I should probably keep the warning though.

  Paul

> >          return;
> >      }
> >
> > -    p = __map_domain_page(page);
> > +    va = __map_domain_page_global(page);
> > +    if ( !va )
> > +    {
> > +        put_page_and_type(page);
> > +        return;
> > +    }
> >
> > -    *(u32 *)p = 0;
> > +    *(uint32_t *)va = 0;
> >
> > -    unmap_domain_page(p);
> > +    v->arch.hvm_vcpu.viridian.apic_assist.page = page;
> > +    v->arch.hvm_vcpu.viridian.apic_assist.va = va;
> > +}
> > +
> > +static void teardown_apic_assist(struct vcpu *v)
> > +{
> > +    struct page_info *page = v->arch.hvm_vcpu.viridian.apic_assist.page;
> > +    void *va = v->arch.hvm_vcpu.viridian.apic_assist.va;
> > +
> > +    if ( !va )
> > +        return;
> > +
> > +    v->arch.hvm_vcpu.viridian.apic_assist.va = NULL;
> > +    v->arch.hvm_vcpu.viridian.apic_assist.page = NULL;
> >
> > +    unmap_domain_page_global(va);
> >      put_page_and_type(page);
> >  }
> >
> > @@ -374,9 +393,9 @@ int wrmsr_viridian_regs(uint32_t idx, uint64_t val)
> >
> >      case VIRIDIAN_MSR_APIC_ASSIST:
> >          perfc_incr(mshv_wrmsr_apic_msr);
> > -        v->arch.hvm_vcpu.viridian.apic_assist.raw = val;
> > +        v->arch.hvm_vcpu.viridian.apic_assist.msr.raw = val;
> >          dump_apic_assist(v);
> > -        if (v->arch.hvm_vcpu.viridian.apic_assist.fields.enabled)
> > +        if ( v->arch.hvm_vcpu.viridian.apic_assist.msr.fields.enabled )
> >              initialize_apic_assist(v);
> >          break;
> >
> > @@ -485,7 +504,7 @@ int rdmsr_viridian_regs(uint32_t idx, uint64_t *val)
> >
> >      case VIRIDIAN_MSR_APIC_ASSIST:
> >          perfc_incr(mshv_rdmsr_apic_msr);
> > -        *val = v->arch.hvm_vcpu.viridian.apic_assist.raw;
> > +        *val = v->arch.hvm_vcpu.viridian.apic_assist.msr.raw;
> >          break;
> >
> >      case VIRIDIAN_MSR_REFERENCE_TSC:
> > @@ -530,6 +549,7 @@ int viridian_vcpu_init(struct vcpu *v)
> >  void viridian_vcpu_deinit(struct vcpu *v)
> >  {
> >      free_cpumask_var(v->arch.hvm_vcpu.viridian.flush_cpumask);
> > +    teardown_apic_assist(v);
> >  }
> >
> >  int viridian_hypercall(struct cpu_user_regs *regs)
> > @@ -728,7 +748,7 @@ static int viridian_save_vcpu_ctxt(struct domain *d,
> hvm_domain_context_t *h)
> >      for_each_vcpu( d, v ) {
> >          struct hvm_viridian_vcpu_context ctxt;
> >
> > -        ctxt.apic_assist = v->arch.hvm_vcpu.viridian.apic_assist.raw;
> > +        ctxt.apic_assist = v->arch.hvm_vcpu.viridian.apic_assist.msr.raw;
> >
> >          if ( hvm_save_entry(VIRIDIAN_VCPU, v->vcpu_id, h, &ctxt) != 0 )
> >              return 1;
> > @@ -754,7 +774,9 @@ static int viridian_load_vcpu_ctxt(struct domain *d,
> hvm_domain_context_t *h)
> >      if ( hvm_load_entry(VIRIDIAN_VCPU, h, &ctxt) != 0 )
> >          return -EINVAL;
> >
> > -    v->arch.hvm_vcpu.viridian.apic_assist.raw = ctxt.apic_assist;
> > +    v->arch.hvm_vcpu.viridian.apic_assist.msr.raw = ctxt.apic_assist;
> > +    if ( v->arch.hvm_vcpu.viridian.apic_assist.msr.fields.enabled )
> > +        initialize_apic_assist(v);
> >
> >      return 0;
> >  }
> > diff --git a/xen/include/asm-x86/hvm/viridian.h b/xen/include/asm-
> x86/hvm/viridian.h
> > index 2eec85e..c60c113 100644
> > --- a/xen/include/asm-x86/hvm/viridian.h
> > +++ b/xen/include/asm-x86/hvm/viridian.h
> > @@ -21,7 +21,11 @@ union viridian_apic_assist
> >
> >  struct viridian_vcpu
> >  {
> > -    union viridian_apic_assist apic_assist;
> > +    struct {
> > +        union viridian_apic_assist msr;
> > +        struct page_info *page;
> > +        void *va;
> > +    } apic_assist;
> >      cpumask_var_t flush_cpumask;
> >  };
> >
> > --
> > 2.1.4
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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