Re: [Xen-devel] [v6][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Chen, Tiejun
> Sent: Tuesday, July 29, 2014 6:36 PM
> 
> Its used conveniently to create RMRR mapping in shared EPT case.
> 
> Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> ---
>  xen/arch/x86/mm/p2m.c     | 29 +++++++++++++++++++++++++++++
>  xen/include/asm-x86/p2m.h |  3 +++
>  2 files changed, 32 insertions(+)
> 
> v6:
> 
> * Refactor set_identity_p2m_entry to make sense
> 
> v5:
> 
> * Rename this function as set_identity_p2m_entry()
> * Get mfn directly inside set_identity_p2m_entry()
> 
> v4:
> 
> * new patch to combine get and set together to create RMRR mapping.
> 
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 642ec28..06bed7a 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -858,6 +858,35 @@ int set_mmio_p2m_entry(struct domain *d, unsigned
> long gfn, mfn_t mfn)
>      return set_typed_p2m_entry(d, gfn, mfn, p2m_mmio_direct);
>  }
> 
> +int set_identity_p2m_entry(struct domain *d, unsigned long gfn)
> +{
> +    p2m_type_t p2mt;
> +    p2m_access_t a;
> +    mfn_t mfn;
> +    struct p2m_domain *p2m = p2m_get_hostp2m(d);
> +    int ret = -EBUSY;
> +
> +    gfn_lock(p2m, gfn, 0);
> +
> +    mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL);
> +
> +    if ( !mfn_valid(mfn) )
> +        ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K,
> p2m_mmio_direct,
> +                            p2m_access_rw);
> +    else if ( mfn_x(mfn) == gfn &&
> +              p2mt == p2m_mmio_direct &&
> +              a == p2m_access_rw )
> +        ret = 0;
> +    else
> +        printk(XENLOG_G_WARNING
> +               "Cannot identity map d%d:%lx, already mapped to %lx.\n",
> +               d->domain_id, gfn, mfn_x(mfn));

what about !mfn_valid but the GFN has been used for emulated MMIOs? w/o
a guest e820 view you can't avoid overlapping by just looking at mfn...

Thanks
Kevin

> +
> +    gfn_unlock(p2m, gfn, 0);
> +
> +    return ret;
> +}
> +
>  /* Returns: 0 for success, -errno for failure */
>  int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn)
>  {
> diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
> index 0ddbadb..d130f9a 100644
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -536,6 +536,9 @@ int p2m_is_logdirty_range(struct p2m_domain *,
> unsigned long start,
>  int set_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn);
>  int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn);
> 
> +/* Set identity addresses in the p2m table (for pass-through) */
> +int set_identity_p2m_entry(struct domain *d, unsigned long gfn);
> +
>  /* Add foreign mapping to the guest's p2m table. */
>  int p2m_add_foreign(struct domain *tdom, unsigned long fgfn,
>                      unsigned long gpfn, domid_t foreign_domid);
> --
> 1.9.1


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