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Re: [Qemu-devel] [PATCH v2 5/6] x86: fix up 32 bit phys_bits case
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH v2 5/6] x86: fix up 32 bit phys_bits case |
Date: |
Tue, 5 Jul 2016 12:55:43 +0100 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Tue, Jul 05, 2016 at 12:29:30PM +0100, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrange (address@hidden) wrote:
> > On Mon, Jul 04, 2016 at 08:16:08PM +0100, Dr. David Alan Gilbert (git)
> > wrote:
> > > From: "Dr. David Alan Gilbert" <address@hidden>
> > >
> > > On 32 bit systems fix up phys_bits to be consistent with what
> > > we tell the guest; don't ever bother with using the phys_bits
> > > property.
> >
> > > @@ -2990,6 +2986,15 @@ static void x86_cpu_realizefn(DeviceState *dev,
> > > Error **errp)
> > > cpu->phys_bits = host_phys_bits;
> > >
> > > }
> > > + } else {
> > > + /* For 32 bit systems don't use the user set value, but keep
> > > + * phys_bits consistent with what we tell the guest.
> > > + */
> > > + if (env->features[FEAT_1_EDX] & CPUID_PSE36) {
> > > + cpu->phys_bits = 36;
> > > + } else {
> > > + cpu->phys_bits = 32;
> > > + }
> >
> > I kind of feel like we should report an error and exit if the
> > user/app has provided a phys_bits property value, rather than
> > silently ignoring their provided value, on the basis that this
> > is a user/app configuration error.
>
> Do we have an easy way to tell that the user has set the parameter
> as opposed to it being the default?
Not sure if there's an official way, but you could perhaps default
phys_bits to -1, and treat -1 as being equivalent to 0 if set by
the user.
Regards,
Daniel
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- Re: [Qemu-devel] [PATCH v2 3/6] x86: fill high bits of mtrr mask, (continued)
[Qemu-devel] [PATCH v2 6/6] x86: Add sanity checks on phys_bits, Dr. David Alan Gilbert (git), 2016/07/04
Re: [Qemu-devel] [PATCH v2 0/6] x86: Physical address limit patches, Michael S. Tsirkin, 2016/07/04