Re: [Xen-devel] [PATCH v4 08/15] x86/altp2m: add control of suppress_ve.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.07.15 at 02:52, <edmund.h.white@xxxxxxxxx> wrote:
> @@ -1528,16 +1528,17 @@ bool_t p2m_mem_access_check(paddr_t gpa, unsigned 
> long gla,
>      vm_event_request_t *req;
>      int rc;
>      unsigned long eip = guest_cpu_user_regs()->eip;
> +    bool_t sve;
>  
>      /* First, handle rx2rw conversion automatically.
>       * These calls to p2m->set_entry() must succeed: we have the gfn
>       * locked and just did a successful get_entry(). */
>      gfn_lock(p2m, gfn, 0);
> -    mfn = p2m->get_entry(p2m, gfn, &p2mt, &p2ma, 0, NULL);
> +    mfn = p2m->get_entry(p2m, gfn, &p2mt, &p2ma, 0, NULL, &sve);
>  
>      if ( npfec.write_access && p2ma == p2m_access_rx2rw ) 
>      {
> -        rc = p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2mt, 
> p2m_access_rw);
> +        rc = p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2mt, 
> p2m_access_rw, sve);
>          ASSERT(rc == 0);
>          gfn_unlock(p2m, gfn, 0);
>          return 1;
> @@ -1546,7 +1547,7 @@ bool_t p2m_mem_access_check(paddr_t gpa, unsigned long 
> gla,
>      {
>          ASSERT(npfec.write_access || npfec.read_access || npfec.insn_fetch);
>          rc = p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K,
> -                            p2mt, p2m_access_rwx);
> +                            p2mt, p2m_access_rwx, -1);

So why -1 here ...

> @@ -1566,14 +1567,14 @@ bool_t p2m_mem_access_check(paddr_t gpa, unsigned 
> long gla,
>          else
>          {
>              gfn_lock(p2m, gfn, 0);
> -            mfn = p2m->get_entry(p2m, gfn, &p2mt, &p2ma, 0, NULL);
> +            mfn = p2m->get_entry(p2m, gfn, &p2mt, &p2ma, 0, NULL, &sve);
>              if ( p2ma != p2m_access_n2rwx )
>              {
>                  /* A listener is not required, so clear the access
>                   * restrictions.  This set must succeed: we have the
>                   * gfn locked and just did a successful get_entry(). */
>                  rc = p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K,
> -                                    p2mt, p2m_access_rwx);
> +                                    p2mt, p2m_access_rwx, sve);

... but sve here, when -1 means "retain current setting" anyway?
(Same question applies elsewhere.)

While I'd preferable see this simplified, either way
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>


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