Re: Xen PVH domU start-of-day VCPU state

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, May 26, 2020 at 10:52:21AM +0200, Martin Lucina wrote:
> On Monday, 25.05.2020 at 17:59, Andrew Cooper wrote:
> > On 25/05/2020 17:42, Jürgen Groß wrote:
> > > You need to setup virtual addressing and enable 64 bit mode before using
> > > 64-bit GDT.
> > >
> > > See Mini-OS source arch/x86/x86_hvm.S
> > 
> > Or
> > https://xenbits.xen.org/gitweb/?p=people/andrewcoop/xen-test-framework.git;a=blob;f=arch/x86/hvm/head.S;h=f7dc72b58ab9ec68538f0087969ab6f72d181d80;hb=HEAD
> > 
> > But yes - Juergen is correct.  Until you have enabled long mode, lgdt
> > will only load the bottom 32 bits of GDTR.base.
> 
> Ah, I missed Jurgen's and your reply here.
> 
> LGDT loading only the bottom 32 bits of GDTR.base shouldn't matter.
> Examining gdt_ptr some more:
> 
>     (gdb) set architecture i386
>     The target architecture is assumed to be i386
>     (gdb) x /xh 0x108040
>     0x108040: 0x002f
>     (gdb) x /xw 0x108042
>     0x108042: 0x00108000
>     (gdb) x /6xb 0x108040
>     0x108040: 0x2f    0x00    0x00    0x80    0x10    0x00
>     (gdb) x /8xb 0x108040
>     0x108040: 0x2f    0x00    0x00    0x80    0x10    0x00    0x00    0x00

Could you also print the GDT entry at 0x10 (ie: 0x108000 + 0x10), just
to make sure it contains the right descriptor?

Roger.