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Re: [Xen-devel] [PATCH v6 1/2] xen/pvh: use a custom IO bitmap for PVH hardware domains

On 05/15/2015 03:42 AM, Jan Beulich wrote:
On 15.05.15 at 09:34, <roger.pau@xxxxxxxxxx> wrote:
El 15/05/15 a les 8.36, Jan Beulich ha escrit:
On 14.05.15 at 17:27, <roger.pau@xxxxxxxxxx> wrote:
El 13/05/15 a les 11.53, Jan Beulich ha escrit:
On 11.05.15 at 16:57, <roger.pau@xxxxxxxxxx> wrote:
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -42,6 +42,7 @@
  #include <xsm/xsm.h>
  #include <xen/trace.h>
  #include <xen/tmem.h>
+#include <asm/setup.h>

  /* Linux config option: propageted to domain0 */
  /* xen_processor_pmbits: xen control Cx, Px, ... */
@@ -219,6 +220,7 @@ static int late_hwdom_init(struct domain *d)
      rangeset_swap(d->iomem_caps, dom0->iomem_caps);
  #ifdef CONFIG_X86
      rangeset_swap(d->arch.ioport_caps, dom0->arch.ioport_caps);
+    setup_io_bitmap(d);

Considering that rangesets are getting swapped rather than
copied, I think you also need to reset Dom0's I/O bitmap here
to the ordinary, non-hardware domain one.

Yes. Would it be fine to memset it and just call setup_io_bitmap on it
again, or would you prefer to exchange it with the static one and free it?

Following how the rangesets are being treated, simply swapping
the two I/O bitmaps would seem to be the right approach here.

AFAICT this requires adding a new hook in hvm_function_table in order to
implement setting the io bitmap for SVM and VMX. I don't have a problem
with that, but it's going to need a separate patch.

Right - if there is nothing like that currently, it'll need to be added.
Of course you may want to get Daniel de Graaf's (who originally
added this non-Dom0 hardware domain code, now Cc-ed) input on
the above outline approach before going that route...

Currently, the only user of this code that I know of is a domain builder
which is a PV stub domain, which may impact a trivial swapping operation
because dom0->arch.hvm_domain will not be valid.  The primary reason why
the rangeset_swap calls are not rangeset_dup is because this stub domain
does not need access to the hardware after the creation of the hardware

I think it seems cleaner for the IO bitmap of domain 0 to also be cleared
after the hardware domain is created, but it's not really a requirement to
make things work.

Daniel De Graaf
National Security Agency

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