[PATCH 12/16] x86/domain_page: remove the fast paths when mfn is not in the directmap

[Hongyan Xia <hx242@xen.org>]

From: Hongyan Xia <hongyxia@amazon.com>

When mfn is not in direct map, never use mfn_to_virt for any mappings.

We replace mfn_x(mfn) <= PFN_DOWN(__pa(HYPERVISOR_VIRT_END - 1)) with
arch_mfn_in_direct_map(mfn) because these two are equivalent. The
extra comparison in arch_mfn_in_direct_map() looks different but because
DIRECTMAP_VIRT_END is always higher, it does not make any difference.

Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
---
 xen/arch/x86/domain_page.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/domain_page.c b/xen/arch/x86/domain_page.c
index 7b22e7c6ed..fc705f056e 100644
--- a/xen/arch/x86/domain_page.c
+++ b/xen/arch/x86/domain_page.c
@@ -14,8 +14,10 @@
 #include <xen/sched.h>
 #include <xen/vmap.h>
 #include <asm/current.h>
+#include <asm/fixmap.h>
 #include <asm/flushtlb.h>
 #include <asm/hardirq.h>
+#include <asm/pmap.h>
 #include <asm/setup.h>
 
 static DEFINE_PER_CPU(struct vcpu *, override);
@@ -35,10 +37,11 @@ static inline struct vcpu *mapcache_current_vcpu(void)
     /*
      * When using efi runtime page tables, we have the equivalent of the idle
      * domain's page tables but current may point at another domain's VCPU.
-     * Return NULL as though current is not properly set up yet.
+     * Return the idle domains's vcpu on that core because the efi per-domain
+     * region (where the mapcache is) is in-sync with the idle domain.
      */
     if ( efi_rs_using_pgtables() )
-        return NULL;
+        return idle_vcpu[smp_processor_id()];
 
     /*
      * If guest_table is NULL, and we are running a paravirtualised guest,
@@ -77,18 +80,24 @@ void *map_domain_page(mfn_t mfn)
     struct vcpu_maphash_entry *hashent;
 
 #ifdef NDEBUG
-    if ( mfn_x(mfn) <= PFN_DOWN(__pa(HYPERVISOR_VIRT_END - 1)) )
+    if ( arch_mfn_in_directmap(mfn_x(mfn)) )
         return mfn_to_virt(mfn_x(mfn));
 #endif
 
     v = mapcache_current_vcpu();
-    if ( !v )
-        return mfn_to_virt(mfn_x(mfn));
+    if ( !v || !v->domain->arch.mapcache.inuse )
+    {
+        if ( arch_mfn_in_directmap(mfn_x(mfn)) )
+            return mfn_to_virt(mfn_x(mfn));
+        else
+        {
+            BUG_ON(system_state >= SYS_STATE_smp_boot);
+            return pmap_map(mfn);
+        }
+    }
 
     dcache = &v->domain->arch.mapcache;
     vcache = &v->arch.mapcache;
-    if ( !dcache->inuse )
-        return mfn_to_virt(mfn_x(mfn));
 
     perfc_incr(map_domain_page_count);
 
@@ -184,6 +193,12 @@ void unmap_domain_page(const void *ptr)
     if ( va >= DIRECTMAP_VIRT_START )
         return;
 
+    if ( va >= FIXADDR_START && va < FIXADDR_TOP )
+    {
+        pmap_unmap((void *)ptr);
+        return;
+    }
+
     ASSERT(va >= MAPCACHE_VIRT_START && va < MAPCACHE_VIRT_END);
 
     v = mapcache_current_vcpu();
@@ -237,7 +252,7 @@ int mapcache_domain_init(struct domain *d)
     unsigned int bitmap_pages;
 
 #ifdef NDEBUG
-    if ( !mem_hotplug && max_page <= PFN_DOWN(__pa(HYPERVISOR_VIRT_END - 1)) )
+    if ( !mem_hotplug && arch_mfn_in_directmap(max_page) )
         return 0;
 #endif
 
@@ -308,7 +323,7 @@ void *map_domain_page_global(mfn_t mfn)
             local_irq_is_enabled()));
 
 #ifdef NDEBUG
-    if ( mfn_x(mfn) <= PFN_DOWN(__pa(HYPERVISOR_VIRT_END - 1)) )
+    if ( arch_mfn_in_directmap(mfn_x(mfn)) )
         return mfn_to_virt(mfn_x(mfn));
 #endif
 
-- 
2.24.1.AMZN