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



On 2014/8/1 6:29, Tian, Kevin wrote:
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...

What about the follows based on this patch?

@@ -865,14 +865,26 @@ int set_identity_p2m_entry(struct domain *d, unsigned long gfn)
     mfn_t mfn;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     int ret = -EBUSY;
+    u64 base_addr, end_addr;

     gfn_lock(p2m, gfn, 0);

     mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL);

     if ( !mfn_valid(mfn) )
+    {
+        base_addr = gfn << PAGE_ORDER_4K;
+        end_addr = base_addr + PAGE_MASK;
+ if ( (!page_is_ram_type(paddr_to_pfn(base_addr), RAM_TYPE_RESERVED)) || + (!page_is_ram_type(paddr_to_pfn(end_add), RAM_TYPE_RESERVED)) )
+        {
+            gfn_unlock(p2m, gfn, 0);
+            return ret;
+        }
+
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 )

Note this chunk of codes just show what I want to do, without test.

Thanks
Tiejun


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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