[Xen-devel] [PATCH v4 27/39] arm/p2m: 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>
---
v3: Cosmetic fixes.

    Changed the locking mechanism to "p2m_write_lock" inside the
    function "altp2m_reset".

    Removed TLB flushing and resetting of the max_mapped_gfn
    lowest_mapped_gfn fields within the function "altp2m_reset". These
    operations are performed in the function "p2m_flush_table".

    Protected altp2m_active(d) check in "altp2m_propagate_change".

    The function "altp2m_propagate_change" now decides whether an entry
    needs to be dropped out of the altp2m view only if the smfn value
    equals INVALID_MFN.

    Extended the function "altp2m_propagate_change" so that it returns
    an int value to the caller. Also, the function "apply_p2m_changes"
    checks the return value and fails the entire operation on error.

    Moved the funtion "modify_altp2m_range" out of this commit.

v4: Use the functions "p2m_(set|get)_entry" instead of the helpers
    "p2m_lookup_attr" and "modify_altp2m_entry".
---
 xen/arch/arm/altp2m.c        | 84 ++++++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/p2m.c           |  4 +++
 xen/include/asm-arm/altp2m.h |  8 +++++
 3 files changed, 96 insertions(+)

diff --git a/xen/arch/arm/altp2m.c b/xen/arch/arm/altp2m.c
index 8c3212780a..4883b1323b 100644
--- a/xen/arch/arm/altp2m.c
+++ b/xen/arch/arm/altp2m.c
@@ -123,6 +123,90 @@ int altp2m_set_mem_access(struct domain *d,
     return rc;
 }
 
+static inline void altp2m_reset(struct p2m_domain *p2m)
+{
+    p2m_write_lock(p2m);
+    p2m_flush_table(p2m);
+    p2m_write_unlock(p2m);
+}
+
+int altp2m_propagate_change(struct domain *d,
+                            gfn_t sgfn,
+                            unsigned int page_order,
+                            mfn_t smfn,
+                            p2m_type_t p2mt,
+                            p2m_access_t p2ma)
+{
+    int rc = 0;
+    unsigned int i;
+    unsigned int reset_count = 0;
+    unsigned int last_reset_idx = ~0;
+    struct p2m_domain *p2m;
+    mfn_t m;
+
+    altp2m_lock(d);
+
+    if ( !altp2m_active(d) )
+        goto out;
+
+    for ( i = 0; i < MAX_ALTP2M; i++ )
+    {
+        p2m = d->arch.altp2m_p2m[i];
+
+        if ( p2m == NULL )
+            continue;
+
+        /*
+         * Get the altp2m mapping. If the smfn has not been dropped, a valid
+         * altp2m mapping needs to be changed/modified accordingly.
+         */
+        p2m_read_lock(p2m);
+        m = p2m_get_entry(p2m, sgfn, NULL, NULL, NULL);
+        p2m_read_unlock(p2m);
+
+        /* Check for a dropped page that may impact this altp2m. */
+        if ( mfn_eq(smfn, INVALID_MFN) &&
+             (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++ )
+                {
+                    p2m = d->arch.altp2m_p2m[i];
+
+                    if ( i == last_reset_idx || p2m == NULL )
+                        continue;
+
+                    altp2m_reset(p2m);
+                }
+                goto out;
+            }
+        }
+        else if ( !mfn_eq(m, INVALID_MFN) )
+        {
+            /* Align the gfn and mfn to the given pager order. */
+            sgfn = _gfn(gfn_x(sgfn) & ~((1UL << page_order) - 1));
+            smfn = _mfn(mfn_x(smfn) & ~((1UL << page_order) - 1));
+
+            p2m_write_lock(p2m);
+            rc = p2m_set_entry(p2m, sgfn, (1UL << page_order), smfn, p2mt, 
p2ma);
+            p2m_write_unlock(p2m);
+        }
+    }
+
+out:
+    altp2m_unlock(d);
+
+    return rc;
+}
+
 static void altp2m_vcpu_reset(struct vcpu *v)
 {
     v->arch.ap2m_idx = INVALID_ALTP2M;
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index e9274c74a8..dcf7be6439 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -958,6 +958,10 @@ static int __p2m_set_entry(struct p2m_domain *p2m,
     else
         rc = 0;
 
+    /* Update all affected altp2m views if necessary. */
+    if ( p2m_is_hostp2m(p2m) )
+        rc = altp2m_propagate_change(p2m->domain, sgfn, page_order, smfn, t, 
a);
+
 out:
     unmap_domain_page(table);
 
diff --git a/xen/include/asm-arm/altp2m.h b/xen/include/asm-arm/altp2m.h
index f8e772f120..3e418cb0f0 100644
--- a/xen/include/asm-arm/altp2m.h
+++ b/xen/include/asm-arm/altp2m.h
@@ -80,4 +80,12 @@ int altp2m_set_mem_access(struct domain *d,
                           p2m_access_t a,
                           gfn_t gfn);
 
+/* Propagates changes made to hostp2m to affected altp2m views. */
+int altp2m_propagate_change(struct domain *d,
+                            gfn_t sgfn,
+                            unsigned int page_order,
+                            mfn_t smfn,
+                            p2m_type_t p2mt,
+                            p2m_access_t p2ma);
+
 #endif /* __ASM_ARM_ALTP2M_H */
-- 
2.13.3


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