Re: [Xen-devel] [PATCH] libxc: Add xc_domain_hvm_get_mtrr_type() call

[Razvan Cojocaru <rzvncj@xxxxxxxxx>]

> >      m->overlapped = is_var_mtrr_overlapped(m);
> >
> > Looks like that function contains the necessary logic.
> You're right, but what happens there is that that function depends on
> the get_mtrr_range() function, which in turn depends on the size_or_mask
> global variable, which is initialized in hvm_mtrr_pat_init(), which then
> depends on a global table, and so on. Putting that into libxc is pretty
> much putting the whole mtrr.c file there.
This is where it gets tricky:

static void get_mtrr_range(uint64_t base_msr, uint64_t mask_msr,
                           uint64_t *base, uint64_t *end)
{
    [...]
    phys_addr = 36;

    if ( cpuid_eax(0x80000000) >= 0x80000008 )
        phys_addr = (uint8_t)cpuid_eax(0x80000008);

    size_or_mask = ~((1 << (phys_addr - PAGE_SHIFT)) - 1);
    [...]
}

specifically, in the cpuid_eax() call, which doesn't make much sense in 
dom0 userspace.
I did manage to take 'enabled' into account with what appears to be 
success, but if I've read the situation correctly, there's not much to 
do about 'overlap', unless we save it in hvm_save_mtrr_msr() like it's 
done with 'enabled'. What do you think?
Thanks,
Razvan Cojocaru

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