[Xen-devel] [PATCH v2 14/25] arm/altp2m: Make get_page_from_gva ready for altp2m.

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

The function get_page_from_gva uses ARM's hardware support to translate
gva's to machine addresses. This function is used, among others, for
memory regulation purposes, e.g, within the context of memory ballooning.
To ensure correct behavior while altp2m is in use, we use the host's p2m
table for the associated gva to ma translation. This is required at this
point, as altp2m lazily copies pages from the host's p2m and even might
be flushed because of changes to the host's p2m (as it is done within
the context of memory ballooning).

Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/p2m.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index bcad51f..784f8da 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1614,7 +1614,7 @@ struct page_info *get_page_from_gva(struct vcpu *v, 
vaddr_t va,
                                     unsigned long flags)
 {
     struct domain *d = v->domain;
-    struct p2m_domain *p2m = &d->arch.p2m;
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
     struct page_info *page = NULL;
     paddr_t maddr = 0;
     int rc;
@@ -1628,7 +1628,34 @@ struct page_info *get_page_from_gva(struct vcpu *v, 
vaddr_t va,
 
     p2m_read_lock(p2m);
 
-    rc = gvirt_to_maddr(va, &maddr, flags);
+    /*
+     * If altp2m is active, we still read the gva from the hostp2m, as it
+     * contains all valid mappings while the currently active altp2m view might
+     * not have the required gva mapping yet.
+     */
+    if ( unlikely(altp2m_active(d)) )
+    {
+        unsigned long irq_flags = 0;
+        uint64_t ovttbr = READ_SYSREG64(VTTBR_EL2);
+
+        if ( ovttbr != p2m->vttbr.vttbr )
+        {
+            local_irq_save(irq_flags);
+            WRITE_SYSREG64(p2m->vttbr.vttbr, VTTBR_EL2);
+            isb();
+        }
+
+        rc = gvirt_to_maddr(va, &maddr, flags);
+
+        if ( ovttbr != p2m->vttbr.vttbr )
+        {
+            WRITE_SYSREG64(ovttbr, VTTBR_EL2);
+            isb();
+            local_irq_restore(irq_flags);
+        }
+    }
+    else
+        rc = gvirt_to_maddr(va, &maddr, flags);
 
     if ( rc )
         goto err;
-- 
2.9.0


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