Re: [Xen-devel] [V10 PATCH 09/23] PVH xen: introduce pvh_set_vcpu_info() and vmx_pvh_set_vcpu_info()

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Mon, 05 Aug 2013 12:08:50 +0100
"Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> >>> On 26.07.13 at 02:58, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> >>> wrote:
> > On Thu, 25 Jul 2013 14:47:55 +0100
> > Tim Deegan <tim@xxxxxxx> wrote:
> > 
> >> At 18:59 -0700 on 23 Jul (1374605957), Mukesh Rathor wrote:
> > ....
> >> > + * Set vmcs fields in support of vcpu_op -> VCPUOP_initialise
> >> > hcall.  Called
> >> > require the
> >> > + *       guest to have same hidden values as the default values
> >> > loaded in the
> >> > + *       vmcs in pvh_construct_vmcs(), ie, the GDT the vcpu is
> >> > coming up on
> >> > + *       should be something like following,
> >> > + *       (from 64bit linux, CS:0x10 DS/SS:0x18) :
> >> > + *
> >> > + *           ffff88007f704000:  0000000000000000
> >> > 00cf9b000000ffff
> >> > + *           ffff88007f704010:  00af9b000000ffff
> >> > 00cf93000000ffff
> >> > + *           ffff88007f704020:  00cffb000000ffff
> >> > 00cff3000000ffff
> >> 
> >> What a bizarre interface!  Why does this operation not load the
> >> hidden parts from the GDT/LDT that the caller supplied?
> > 
> > Pl see:
> > http://lists.xen.org/archives/html/xen-devel/2013-07/msg01489.html 
> > 
> > That was an option discussed with Jan, walking and reading the GDT
> > entries from the gdtaddr the guest provided to load the hidden
> > parts. But, I agree with him, that for the initial cpu boot we can
> > restrict the ABI to say: 0 base addr, ~0 limit, and "read/write,
> > accessed" default attributes for the hidden part (64bit guest). 
> 
> That must be a misunderstanding then (also see my other reply) - I
> always meant to require that you either properly load the hidden
> register portions from the descriptor tables, or at least verify that
> the descriptor table entries referenced match the defaults you
> enforce.

Ok, I thought you just wanted to be documented, If I'm gonna write
the code to verify, i might as well just write the hidden porions, an
option I'd proposed. That way there are no constraints. I'm currently
working on just doing that, and will be in the next version of the patch.

thanks
mukesh



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