[Xen-devel] [PATCH v2 19/25] arm/altp2m: Add altp2m_propagate_change.

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

This commit introduces the function "altp2m_propagate_change" that is
responsible to propagate changes applied to the host's p2m to a specific
or even all altp2m views. In this way, Xen can in-/decrease the guest's
physmem at run-time without leaving the altp2m views with
stalled/invalid entries.

Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/altp2m.c        | 75 ++++++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/p2m.c           | 14 +++++++++
 xen/include/asm-arm/altp2m.h |  9 ++++++
 xen/include/asm-arm/p2m.h    |  5 +++
 4 files changed, 103 insertions(+)

diff --git a/xen/arch/arm/altp2m.c b/xen/arch/arm/altp2m.c
index f98fd73..f3c1cff 100644
--- a/xen/arch/arm/altp2m.c
+++ b/xen/arch/arm/altp2m.c
@@ -133,6 +133,81 @@ out:
     return rc;
 }
 
+static inline void altp2m_reset(struct p2m_domain *p2m)
+{
+    read_lock(&p2m->lock);
+
+    p2m_flush_table(p2m);
+    p2m_flush_tlb(p2m);
+
+    p2m->lowest_mapped_gfn = INVALID_GFN;
+    p2m->max_mapped_gfn = _gfn(0);
+
+    read_unlock(&p2m->lock);
+}
+
+void altp2m_propagate_change(struct domain *d,
+                             gfn_t sgfn,
+                             unsigned long nr,
+                             mfn_t smfn,
+                             uint32_t mask,
+                             p2m_type_t p2mt,
+                             p2m_access_t p2ma)
+{
+    struct p2m_domain *p2m;
+    mfn_t m;
+    unsigned int i;
+    unsigned int reset_count = 0;
+    unsigned int last_reset_idx = ~0;
+
+    if ( !altp2m_active(d) )
+        return;
+
+    altp2m_lock(d);
+
+    for ( i = 0; i < MAX_ALTP2M; i++ )
+    {
+        if ( d->arch.altp2m_vttbr[i] == INVALID_VTTBR )
+            continue;
+
+        p2m = d->arch.altp2m_p2m[i];
+
+        m = p2m_lookup_attr(p2m, sgfn, NULL, NULL, NULL, NULL);
+
+        /* Check for a dropped page that may impact this altp2m. */
+        if ( (mfn_eq(smfn, INVALID_MFN) || p2mt == p2m_invalid) &&
+             gfn_x(sgfn) >= gfn_x(p2m->lowest_mapped_gfn) &&
+             gfn_x(sgfn) <= gfn_x(p2m->max_mapped_gfn) )
+        {
+            if ( !reset_count++ )
+            {
+                altp2m_reset(p2m);
+                last_reset_idx = i;
+            }
+            else
+            {
+                /* At least 2 altp2m's impacted, so reset everything. */
+                for ( i = 0; i < MAX_ALTP2M; i++ )
+                {
+                    if ( i == last_reset_idx ||
+                         d->arch.altp2m_vttbr[i] == INVALID_VTTBR )
+                        continue;
+
+                    p2m = d->arch.altp2m_p2m[i];
+                    altp2m_reset(p2m);
+                }
+                goto out;
+            }
+        }
+        else if ( !mfn_eq(m, INVALID_MFN) )
+            modify_altp2m_range(d, p2m, sgfn, nr, smfn,
+                                mask, p2mt, p2ma);
+    }
+
+out:
+    altp2m_unlock(d);
+}
+
 static void altp2m_vcpu_reset(struct vcpu *v)
 {
     struct altp2mvcpu *av = &vcpu_altp2m(v);
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index e0a7f38..31810e6 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -992,6 +992,7 @@ static int apply_p2m_changes(struct domain *d,
     const bool_t preempt = !is_idle_vcpu(current);
     bool_t flush = false;
     bool_t flush_pt;
+    bool_t entry_written = false;
     PAGE_LIST_HEAD(free_pages);
     struct page_info *pg;
 
@@ -1112,6 +1113,7 @@ static int apply_p2m_changes(struct domain *d,
                                   &addr, &maddr, &flush,
                                   t, a);
             if ( ret < 0 ) { rc = ret ; goto out; }
+            if ( ret ) entry_written = 1;
             count += ret;
 
             if ( ret != P2M_ONE_PROGRESS_NOP )
@@ -1208,6 +1210,9 @@ out:
 
     p2m_write_unlock(p2m);
 
+    if ( rc >= 0 && entry_written && p2m_is_hostp2m(p2m) )
+        altp2m_propagate_change(d, sgfn, nr, smfn, mask, t, a);
+
     if ( rc < 0 && ( op == INSERT ) &&
          addr != start_gpaddr )
     {
@@ -1331,6 +1336,15 @@ int modify_altp2m_entry(struct domain *d, struct 
p2m_domain *ap2m,
     return apply_p2m_changes(d, ap2m, INSERT, gfn, nr, mfn, 0, t, a);
 }
 
+int modify_altp2m_range(struct domain *d, struct p2m_domain *ap2m,
+                        gfn_t sgfn, unsigned long nr, mfn_t smfn,
+                        uint32_t m, p2m_type_t t, p2m_access_t a)
+{
+    ASSERT(p2m_is_altp2m(ap2m));
+
+    return apply_p2m_changes(d, ap2m, INSERT, sgfn, nr, smfn, m, t, a);
+}
+
 int p2m_alloc_table(struct p2m_domain *p2m)
 {
     unsigned int i;
diff --git a/xen/include/asm-arm/altp2m.h b/xen/include/asm-arm/altp2m.h
index dc41f93..9aeb7d6 100644
--- a/xen/include/asm-arm/altp2m.h
+++ b/xen/include/asm-arm/altp2m.h
@@ -81,4 +81,13 @@ int altp2m_set_mem_access(struct domain *d,
                           p2m_access_t a,
                           gfn_t gfn);
 
+/* Propagates changes made to hostp2m to affected altp2m views. */
+void altp2m_propagate_change(struct domain *d,
+                             gfn_t sgfn,
+                             unsigned long nr,
+                             mfn_t smfn,
+                             uint32_t mask,
+                             p2m_type_t p2mt,
+                             p2m_access_t p2ma);
+
 #endif /* __ASM_ARM_ALTP2M_H */
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index 9859ad1..59186c9 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -191,6 +191,11 @@ int modify_altp2m_entry(struct domain *d, struct 
p2m_domain *p2m,
                         paddr_t gpa, paddr_t maddr, unsigned int level,
                         p2m_type_t t, p2m_access_t a);
 
+/* Modify an altp2m view's range of entries or their attributes. */
+int modify_altp2m_range(struct domain *d, struct p2m_domain *p2m,
+                        gfn_t sgfn, unsigned long nr, mfn_t smfn,
+                        uint32_t mask, p2m_type_t t, p2m_access_t a);
+
 /* Clean & invalidate caches corresponding to a region of guest address space 
*/
 int p2m_cache_flush(struct domain *d, gfn_t start, unsigned long nr);
 
-- 
2.9.0


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