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

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Fri, Jul 10, 2015 at 1:52 AM, Ed White <edmund.h.white@xxxxxxxxx> wrote:
> From: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
>
> The existing ept_set_entry() and ept_get_entry() routines are extended
> to optionally set/get suppress_ve.  Passing -1 will set suppress_ve on
> new p2m entries, or retain suppress_ve flag on existing entries.
>
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

So because my patch contained code written by Ed, and this patch now
contains code written by you, I'm pretty sure that a strict observance
of protocol would require his SoB to be retained (as I think I did
when I sent it), and your SoB to be added, for copyright purposes.

In this particular case a lawyer might argue that the code snippets
inquestion were so small or obvious as to be uncopyrightable, but it
doesn't really hurt to be a bit more strict than we need to be. :-)

Also, a description of what you had changed could have helped speed
review. (It seems you've only added the bits requested to the p2m-pt
implementation?)

Finally, one thing I missed in the discussion before...

> @@ -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);
>          ASSERT(rc == 0);
>      }
>      gfn_unlock(p2m, gfn, 0);

This definitely should not be "sve" in the 'if' clause and "-1" in the
'else' clause.  Because I was looking only at the patch, I missed that
when Jan raised the issue before. That's a mistake on my part -- would
you mind doing as Jan suggests, and just making these "NULL" and "-1"
throughout this file?

Thanks!
 -George

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