[RFC PATCH v6 30/43] arm/altp2m: Add altp2m view validity/visibility indicator

[Rose Spangler <Rose.Spangler@xxxxxxxxxxxxxx>]

This commit adds the altp2m_view_state enum, which indicates whether an
altp2m view is invalid, visible, or invisible. The altp2m_state array is
comprised of altp2m_view_state values, where each entry corresponds to the
altp2m view with the same entry. This is analogous to the altp2m_eptp and
altp2m_visible_eptp arrays on x86.

This addition is necessary to tell whether an altp2m is valid, in addition
to whether it is visible. Since all altp2m views are allocated up-front
during p2m initialization, there must be an additional mechanism to
determine whether an altp2m view is valid. Since the implementation of
HVMOP_altp2m_set_visibility also needs an additional mechanism to determine
whether a view is visible, it makes sense to combine altp2m view validity
and visibility into a single mechanism. Therefore, the altp2m_state array
is used to track both view validitity and visibility.

This is commit 1/5 of the altp2m view validity/visibility phase.

Signed-off-by: Rose Spangler <Rose.Spangler@xxxxxxxxxxxxxx>
---
v6: Introduced this patch.

    In the v4/v5 patch series, view validity was determined by simply
    checking if the altp2m p2m_domain pointer is NULL. This isn't possible
    in the v6 patch series, since altp2m views are allocated up-front
    during altp2m_init.

    Since the altp2m_view_state enum definition has to be available in
    asm/domain.h, this commit removes the sched.h dependency from altp2m.h.
    Unfortunately, this means that it's not possible to have static inline
    functions in altp2m.h which need a complete definition of arch_domain
    and arch_vcpu. If there would be a better place to put the
    altp2m_view_state definition, feedback would be appreciated.
---
 xen/arch/arm/altp2m.c             | 13 +++++++++++++
 xen/arch/arm/include/asm/altp2m.h | 23 +++++++++++++----------
 xen/arch/arm/include/asm/domain.h |  4 ++++
 xen/arch/arm/mmu/p2m.c            | 14 +++++++++++++-
 4 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/xen/arch/arm/altp2m.c b/xen/arch/arm/altp2m.c
index 339f82835caf..e741648ff5a1 100644
--- a/xen/arch/arm/altp2m.c
+++ b/xen/arch/arm/altp2m.c
@@ -5,6 +5,8 @@
  * Copyright (c) 2016 Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
  */
 
+#include <xen/sched.h>
+
 #include <asm/p2m.h>
 
 /* Check to see if vcpu should be switched to a different p2m. */
@@ -14,6 +16,17 @@ void altp2m_check(struct vcpu *v, uint16_t idx)
     BUG();
 }
 
+/* Alternate p2m VCPU */
+uint16_t altp2m_vcpu_idx(const struct vcpu *v)
+{
+    return v->arch.ap2m_idx;
+}
+
+void altp2m_set_vcpu_idx(struct vcpu *v, unsigned int idx)
+{
+    v->arch.ap2m_idx = idx;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/arch/arm/include/asm/altp2m.h 
b/xen/arch/arm/include/asm/altp2m.h
index f001e022a213..05beb7f698a7 100644
--- a/xen/arch/arm/include/asm/altp2m.h
+++ b/xen/arch/arm/include/asm/altp2m.h
@@ -9,7 +9,10 @@
 #ifndef __ASM_ARM_ALTP2M_H
 #define __ASM_ARM_ALTP2M_H
 
-#include <xen/sched.h>
+#include <xen/mem_access.h>
+
+struct domain;
+struct vcpu;
 
 #ifdef CONFIG_ALTP2M
 
@@ -24,15 +27,15 @@ static inline bool altp2m_supported(void)
 #define altp2m_unlock(d)    spin_unlock(&(d)->arch.altp2m_lock)
 
 /* Alternate p2m VCPU */
-static inline uint16_t altp2m_vcpu_idx(const struct vcpu *v)
-{
-    return v->arch.ap2m_idx;
-}
-
-static inline void altp2m_set_vcpu_idx(struct vcpu *v, unsigned int idx)
-{
-    v->arch.ap2m_idx = idx;
-}
+uint16_t altp2m_vcpu_idx(const struct vcpu *v);
+void altp2m_set_vcpu_idx(struct vcpu *v, unsigned int idx);
+
+/* The current state of an altp2m view */
+enum altp2m_view_state {
+    ALTP2M_INVALID,
+    ALTP2M_VISIBLE,
+    ALTP2M_INVISIBLE,
+};
 
 #else /* CONFIG_ALTP2M */
 
diff --git a/xen/arch/arm/include/asm/domain.h 
b/xen/arch/arm/include/asm/domain.h
index 4d497a21b648..28533b08db1f 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -3,6 +3,7 @@
 
 #include <xen/cache.h>
 #include <xen/timer.h>
+#include <asm/altp2m.h>
 #include <asm/page.h>
 #include <asm/p2m.h>
 #include <asm/suspend.h>
@@ -135,6 +136,9 @@ struct arch_domain
      * concurrently.
      */
     spinlock_t altp2m_lock;
+
+    /* Validity/visibility of altp2m views */
+    enum altp2m_view_state *altp2m_state;
 #endif
 }  __cacheline_aligned;
 
diff --git a/xen/arch/arm/mmu/p2m.c b/xen/arch/arm/mmu/p2m.c
index 04d17e787259..7c23995f8074 100644
--- a/xen/arch/arm/mmu/p2m.c
+++ b/xen/arch/arm/mmu/p2m.c
@@ -1494,6 +1494,8 @@ int p2m_teardown(struct domain *d)
 
     d->altp2m_active = false;
 
+    FREE_XENHEAP_PAGE(d->arch.altp2m_state);
+
     for ( i = 0; i < d->nr_altp2m; i++ )
     {
         rc = p2m_teardown_one(d->altp2m_p2m[i]);
@@ -1617,7 +1619,7 @@ struct p2m_domain *p2m_init_one(struct domain *d)
 static int p2m_init_altp2m(struct domain *d)
 {
 #ifdef CONFIG_ALTP2M
-    int rc;
+    int rc, i;
 
     rc = altp2m_init(d);
     if ( rc )
@@ -1626,6 +1628,16 @@ static int p2m_init_altp2m(struct domain *d)
         return rc;
     }
 
+    if ( (d->arch.altp2m_state = alloc_xenheap_page()) == NULL )
+    {
+        return -ENOMEM;
+    }
+
+    for ( i = 0; i < d->nr_altp2m; i++ )
+    {
+        d->arch.altp2m_state[i] = ALTP2M_INVALID;
+    }
+
     d->altp2m_active = false;
 #endif
 
-- 
2.34.1