[Xen-devel] Re: One question on MMIO

[Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>]

At 19:39 +0800 on 29 Jun (1183145958), Jiang, Yunhong wrote:
> But why do we use the table_mfn when we update the shadow in 
> shadow_write_p2m_entry()?
>     /* The P2M can be shadowed: keep the shadows synced */
>     if ( d->vcpu[0] != NULL )
>         (void)sh_validate_guest_entry(d->vcpu[0], table_mfn, p, sizeof(*p));
> Where the table_mfn is defined as:
>     mfn_t table_mfn = pagetable_get_mfn(d->arch.phys_table);
> 
> Should we use the corresponding p2m table at that level to do this?

You're right, this is a bug; thank you.  It crept in when the p2m
table-walker was separated from the shadow-specific code.  We get away
with it at the moment because the usual change is from not-present to
present, which is handled correctly by the fast-path code just a little
below, which blows away the whole shadow set.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

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