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Re: [Qemu-devel] [PATCH v4 5/5] x86: Set physical address bits based on
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v4 5/5] x86: Set physical address bits based on host |
Date: |
Mon, 11 Jul 2016 19:47:47 +0100 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
* Eduardo Habkost (address@hidden) wrote:
> On Mon, Jul 11, 2016 at 04:39:22PM +0100, Dr. David Alan Gilbert wrote:
> > * Eduardo Habkost (address@hidden) wrote:
> [...]
> > > > + cpu->phys_bits = TCG_PHYS_ADDR_BITS;
> > > > + }
> > > > } else {
> > > > /* For 32 bit systems don't use the user set value, but keep
> > > > * phys_bits consistent with what we tell the guest.
> > >
> > > Shouldn't we return error if host-phys-bits is set in 32-bit
> > > mode?
> >
> > I've just realised there's a reason that erroring in this case is a problem.
> > Imagine a future (or downstream) machine type that made host-phys-bits the
> > default;
> > how would it run with a 32bit CPU?
>
> Oh, that's right. Ignoring it when explicitly set isn't
> intuitive, but we need to be able to ignore it when set by a
> machine compat_props (or if it's enabled by default). And
> creating two separate properties sounds like overkill...
> I'm reluctant, but I think it's OK to ignore it if LM is not set.
> But we need to make sure it's documented somewhere.
OK, I'll add a comment and a note in the commit message.
Dave
>
> --
> Eduardo
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH v4 3/5] x86: Mask mtrr mask based on CPU physical address limits, (continued)
Re: [Qemu-devel] [PATCH v4 0/5] x86: Physical address limit patches, Eduardo Habkost, 2016/07/08