[RFC 14/22] xen/arm: p2m: Re-implement p2m_cache_flush using p2m_get_entry

[Julien Grall <julien.grall@arm.com>]

The function p2m_cache_flush can be re-implemented using the generic
function p2m_get_entry by iterating over the range and using the mapping
order given by the callee.

As the current implementation, no preemption is implemented, although
the comment in the current code claimed it. As the function is called by
a DOMCTL with a region of 1GB maximum, I think the preemption can be
left unimplemented for now.

Finally drop the operation CACHEFLUSH in apply_one_level as nobody is
using it anymore. Note that the function could have been dropped in one
go at the end, however I find easier to drop the operations one by one
avoiding a big deletion in the patch that convert the last operation.

Signed-off-by: Julien Grall <julien.grall@arm.com>

---
    The loop pattern will be very for the reliquish function. It might
    be possible to extract it in a separate function.
---
 xen/arch/arm/p2m.c | 67 +++++++++++++++++++++++++++---------------------------
 1 file changed, 34 insertions(+), 33 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 9a9c85c..e7697bb 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -722,7 +722,6 @@ enum p2m_operation {
     INSERT,
     REMOVE,
     RELINQUISH,
-    CACHEFLUSH,
     MEMACCESS,
 };
 
@@ -978,36 +977,6 @@ static int apply_one_level(struct domain *d,
          */
         return P2M_ONE_PROGRESS;
 
-    case CACHEFLUSH:
-        if ( !p2m_valid(orig_pte) )
-        {
-            *addr = (*addr + level_size) & level_mask;
-            return P2M_ONE_PROGRESS_NOP;
-        }
-
-        if ( level < 3 && p2m_table(orig_pte) )
-            return P2M_ONE_DESCEND;
-
-        /*
-         * could flush up to the next superpage boundary, but would
-         * need to be careful about preemption, so just do one 4K page
-         * now and return P2M_ONE_PROGRESS{,_NOP} so that the caller will
-         * continue to loop over the rest of the range.
-         */
-        if ( p2m_is_ram(orig_pte.p2m.type) )
-        {
-            unsigned long offset = paddr_to_pfn(*addr & ~level_mask);
-            flush_page_to_ram(orig_pte.p2m.base + offset);
-
-            *addr += PAGE_SIZE;
-            return P2M_ONE_PROGRESS;
-        }
-        else
-        {
-            *addr += PAGE_SIZE;
-            return P2M_ONE_PROGRESS_NOP;
-        }
-
     case MEMACCESS:
         if ( level < 3 )
         {
@@ -1555,12 +1524,44 @@ int p2m_cache_flush(struct domain *d, gfn_t start, unsigned long nr)
 {
     struct p2m_domain *p2m = &d->arch.p2m;
     gfn_t end = gfn_add(start, nr);
+    p2m_type_t t;
+    unsigned int order;
 
     start = gfn_max(start, p2m->lowest_mapped_gfn);
     end = gfn_min(end, p2m->max_mapped_gfn);
 
-    return apply_p2m_changes(d, CACHEFLUSH, start, nr, INVALID_MFN,
-                             0, p2m_invalid, d->arch.p2m.default_access);
+    /* XXX: Should we use write lock here? */
+    p2m_read_lock(p2m);
+
+    for ( ; gfn_x(start) < gfn_x(end); start = gfn_add(start, 1UL << order) )
+    {
+        mfn_t mfn = p2m_get_entry(p2m, start, &t, NULL, &order);
+
+        /* Skip hole and non-RAM page */
+        if ( mfn_eq(mfn, INVALID_MFN) || !p2m_is_ram(t) )
+        {
+            /*
+             * the order corresponds to the order of the mapping in the
+             * page table. so we need to align the gfn before
+             * incrementing.
+             */
+            start = _gfn(gfn_x(start) & ~((1UL << order) - 1));
+            continue;
+        }
+
+        /*
+         * Could flush up to the next superpage boundary, but we would
+         * need to be careful about preemption, so just do one 4K page
+         * now.
+         * XXX: Implement preemption.
+         */
+        flush_page_to_ram(mfn_x(mfn));
+        order = 0;
+    }
+
+    p2m_read_unlock(p2m);
+
+    return 0;
 }
 
 mfn_t gfn_to_mfn(struct domain *d, gfn_t gfn)
-- 
1.9.1


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