Re: [Xen-devel] [RFC PATCH resend] PVH Dom0 RMRR IOMMU mapping regression fix

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.09.15 at 01:53, <elena.ufimtseva@xxxxxxxxxx> wrote:
> Permissions for p2m entry of read-only 
> mmio regions are left unchanged as leaving only 'r' cause page faults. I am 
> not sure what the reason of it yet, will try to dig it further.

Yes please - imo this absolutely should be changed to just r along
with the rwx -> rw conversion. Since you saw page faults, could
you at least point out which address(es) they occurred for? After
all the set of r/o MMIO pages should be relatively small...

> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -971,7 +971,17 @@ int set_identity_p2m_entry(struct domain *d, unsigned 
> long gfn,
>          ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K,
>                              p2m_mmio_direct, p2ma);
>      else if ( mfn_x(mfn) == gfn && p2mt == p2m_mmio_direct && a == p2ma )
> -        ret = 0;
> +    {
> +        /*
> +         * PVH fixme: during Dom0 PVH construction, p2m entries are being set
> +         * but iomem regions are not mapped with IOMMU. This makes sure that
> +         * RMRRs are correctly mapped with IOMMU.
> +         */
> +        if ( is_hardware_domain(d) && !iommu_use_hap_pt(d) )
> +            ret = iommu_map_page(d, gfn, gfn, 
> IOMMUF_readable|IOMMUF_writable);

This should use p2m_get_iommu_flags() (which eventually needs to
also honor the passed in p2m_access_t, i.e. its use here for now
only serves documentation purposes as well as a means to spot the
location when making said adjustment).

Jan


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