Re: [Xen-devel] [PATCH v4 13/24] arm/acpi: Map all other tables for Dom0

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 1 Mar 2016, Shannon Zhao wrote:
> On 2016/2/29 22:15, Stefano Stabellini wrote:
> > On Sun, 28 Feb 2016, Shannon Zhao wrote:
> >> > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> >> > 
> >> > Map all other tables to Dom0 using 1:1 mappings.
> >> > 
> >> > Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> >> > ---
> >> > v4: fix commit message
> >> > ---
> >> >  xen/arch/arm/domain_build.c | 26 ++++++++++++++++++++++++++
> >> >  1 file changed, 26 insertions(+)
> >> > 
> >> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> >> > index 64e48ae..6ad420c 100644
> >> > --- a/xen/arch/arm/domain_build.c
> >> > +++ b/xen/arch/arm/domain_build.c
> >> > @@ -1357,6 +1357,30 @@ static int prepare_dtb(struct domain *d, struct 
> >> > kernel_info *kinfo)
> >> >  }
> >> >  
> >> >  #ifdef CONFIG_ACPI
> >> > +static void acpi_map_other_tables(struct domain *d)
> >> > +{
> >> > +    int i;
> >> > +    unsigned long res;
> >> > +    u64 addr, size;
> >> > +
> >> > +    /* Map all other tables to Dom0 using 1:1 mappings. */
> >> > +    for( i = 0; i < acpi_gbl_root_table_list.count; i++ )
> >> > +    {
> >> > +        addr = acpi_gbl_root_table_list.tables[i].address;
> >> > +        size = acpi_gbl_root_table_list.tables[i].length;
> >> > +        res = map_regions(d,
> >> > +                          paddr_to_pfn(addr & PAGE_MASK),
> >> > +                          DIV_ROUND_UP(size, PAGE_SIZE),
> >> > +                          paddr_to_pfn(addr & PAGE_MASK));
> >> > +        if ( res )
> >> > +        {
> >> > +             panic(XENLOG_ERR "Unable to map 0x%"PRIx64
> >> > +                   " - 0x%"PRIx64" in domain \n",
> >> > +                   addr & PAGE_MASK, PAGE_ALIGN(addr + size) - 1);
> >> > +        }
> >> > +    }
> >> > +}
> > The problem with this function is that it is mapping all other tables to
> > the guest, including the unmodified FADT and MADT. This way dom0 is
> > going to find two different versions of the FADT and MADT, isn't that
> > right?
> >  
> We've replaced the entries of XSDT table with new value. That means XSDT
> points to new table. Guest will not see the old ones.

All right. Of course it would be best to avoid mapping the original FADT
and MADT at all, but given that they are not likely to be page aligned,
it wouldn't be easy to do.

Reviewed-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

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