[Xen-devel] [PATCH v4 22/39] arm/p2m: Make p2m_mem_access_check ready for altp2m

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

This commit extends the function "p2m_mem_access_check" and
"p2m_mem_access_check_and_get_page" to consider altp2m. The function
"p2m_mem_access_check_and_get_page" needs to translate the gva upon the
hostp2m's vttbr, as it contains all valid mappings while the currently
active altp2m view might not have the required gva mapping yet.

Also, the new implementation fills the request buffer to hold
altp2m-related information.

Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
v3: Extended the function "p2m_mem_access_check_and_get_page" to
    consider altp2m. Similar to "get_page_from_gva", the function
    "p2m_mem_access_check_and_get_page" needs to translate the gva upon
    the hostp2m's vttbr. Although, the function "gva_to_ipa" (called in
    "p2m_mem_access_check_and_get_page") performs a stage 1 table walk,
    it will access page tables residing in memory. Accesses to this
    memory are controlled by the underlying 2nd stage translation table
    and hence require the original mappings of the hostp2m.

v4: Cosmetic fixes.

    Initialized the variable "ipa" in the function
    "p2m_mem_access_check_and_get_page" to satisfy compiler warnings.
---
 xen/arch/arm/mem_access.c | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/mem_access.c b/xen/arch/arm/mem_access.c
index 5bc28db8ff..ebc3a86af3 100644
--- a/xen/arch/arm/mem_access.c
+++ b/xen/arch/arm/mem_access.c
@@ -21,6 +21,7 @@
 #include <xen/sched.h>
 #include <xen/vm_event.h>
 #include <public/vm_event.h>
+#include <asm/altp2m.h>
 #include <asm/event.h>
 #include <asm/guest_walk.h>
 
@@ -108,9 +109,31 @@ p2m_mem_access_check_and_get_page(vaddr_t gva, unsigned 
long flag,
     xenmem_access_t xma;
     p2m_type_t t;
     struct page_info *page = NULL;
-    struct p2m_domain *p2m = p2m_get_hostp2m(v->domain);
+    struct domain *d = v->domain;
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+
+    /*
+     * If altp2m is active, we need to translate the gva upon the hostp2m's
+     * vttbr, as it contains all valid mappings while the currently active
+     * altp2m view might not have the required gva mapping yet. Although, the
+     * function gva_to_ipa performs a stage 1 table walk, it will access page
+     * tables residing in memory. Accesses to this memory are controlled by the
+     * underlying 2nd stage translation table and hence require the original
+     * mappings of the hostp2m.
+     */
+    if ( unlikely(altp2m_active(d)) )
+    {
+        unsigned long flags = 0;
+        uint64_t ovttbr = READ_SYSREG64(VTTBR_EL2);
+
+        p2m_switch_vttbr_and_get_flags(ovttbr, p2m->vttbr, flags);
 
-    rc = gva_to_ipa(gva, &ipa, flag);
+        rc = gva_to_ipa(gva, &ipa, flag);
+
+        p2m_restore_vttbr_and_set_flags(ovttbr, flags);
+    }
+    else
+        rc = gva_to_ipa(gva, &ipa, flag);
 
     /*
      * In case mem_access is active, hardware-based gva_to_ipa translation
@@ -225,13 +248,15 @@ bool_t p2m_mem_access_check(paddr_t gpa, vaddr_t gla, 
const struct npfec npfec)
     xenmem_access_t xma;
     vm_event_request_t *req;
     struct vcpu *v = current;
-    struct p2m_domain *p2m = p2m_get_hostp2m(v->domain);
+    struct p2m_domain *p2m = p2m_get_active_p2m(v);
 
     /* Mem_access is not in use. */
     if ( !p2m->mem_access_enabled )
         return true;
 
-    rc = p2m_get_mem_access(v->domain, gaddr_to_gfn(gpa), &xma);
+    p2m_read_lock(p2m);
+    rc = __p2m_get_mem_access(p2m, _gfn(paddr_to_pfn(gpa)), &xma);
+    p2m_read_unlock(p2m);
     if ( rc )
         return true;
 
-- 
2.13.3


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