Re: [PATCH v2.1 06/18] x86/pv: set/clear guest GDT mappings using {populate,destroy}_perdomain_mapping()

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

On Thu, Jan 09, 2025 at 10:25:50AM +0000, Alejandro Vallejo wrote:
> On Wed Jan 8, 2025 at 3:11 PM GMT, Roger Pau Monne wrote:
> > The pv_{set,destroy}_gdt() functions rely on the L1 table(s) that contain 
> > such
> > mappings being stashed in the domain structure, and thus such mappings being
> > modified by merely updating the L1 entries.
> >
> > Switch both pv_{set,destroy}_gdt() to instead use
> > {populate,destory}_perdomain_mapping().
> 
> nit: s/destory/destroy
> 
> How come pv_set_gdt() doesn't need to be reordered here (as opposed to v2)?

In a previous version (that I've never published)
populate_perdomain_mapping() was using v->arch.cr3 as the root pointer
in which to do a page-walk and modify the requested entries.  That
required v->arch.cr3 to be valid when populate_perdomain_mapping() was
called, and hence needed the reordering.

Since populate_perdomain_mapping() no longer uses v->arch.cr3 it
doesn't matter whether the vCPU c3 is valid when calling
populate_perdomain_mapping().

Thanks, Roger.