[PATCH v4 04/18] xen/riscv: construct the P2M pages pool for guests

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Implement p2m_set_allocation() to construct p2m pages pool for guests
based on required number of pages.

This is implemented by:
- Adding a `struct paging_domain` which contains a freelist, a
  counter variable and a spinlock to `struct arch_domain` to
  indicate the free p2m pages and the number of p2m total pages in
  the p2m pages pool.
- Adding a helper `p2m_set_allocation` to set the p2m pages pool
  size. This helper should be called before allocating memory for
  a guest and is called from domain_p2m_set_allocation(), the latter
  is a part of common dom0less code.
- Adding implementation of paging_freelist_adjust() and
  paging_domain_init().

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Changes in V4:
 - s/paging_freelist_init/paging_freelist_adjust.
 - Add empty line between definiton of paging_freelist_adjust()
   and paging_domain_init().
 - Update commit message.
 - Add Acked-by: Jan Beulich <jbeulich@xxxxxxxx>.
---
Changes in v3:
 - Drop usage of p2m_ prefix inside struct paging_domain().
 - Introduce paging_domain_init() to init paging struct.
---
Changes in v2:
 - Drop the comment above inclusion of <xen/event.h> in riscv/p2m.c.
 - Use ACCESS_ONCE() for lhs and rhs for the expressions in
   p2m_set_allocation().
---
 xen/arch/riscv/Makefile             |  1 +
 xen/arch/riscv/include/asm/Makefile |  1 -
 xen/arch/riscv/include/asm/domain.h | 12 ++++++
 xen/arch/riscv/include/asm/paging.h | 13 ++++++
 xen/arch/riscv/p2m.c                | 18 ++++++++
 xen/arch/riscv/paging.c             | 65 +++++++++++++++++++++++++++++
 6 files changed, 109 insertions(+), 1 deletion(-)
 create mode 100644 xen/arch/riscv/include/asm/paging.h
 create mode 100644 xen/arch/riscv/paging.c

diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index e2499210c8..6b912465b9 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -6,6 +6,7 @@ obj-y += imsic.o
 obj-y += intc.o
 obj-y += irq.o
 obj-y += mm.o
+obj-y += paging.o
 obj-y += pt.o
 obj-y += p2m.o
 obj-$(CONFIG_RISCV_64) += riscv64/
diff --git a/xen/arch/riscv/include/asm/Makefile 
b/xen/arch/riscv/include/asm/Makefile
index bfdf186c68..3824f31c39 100644
--- a/xen/arch/riscv/include/asm/Makefile
+++ b/xen/arch/riscv/include/asm/Makefile
@@ -6,7 +6,6 @@ generic-y += hardirq.h
 generic-y += hypercall.h
 generic-y += iocap.h
 generic-y += irq-dt.h
-generic-y += paging.h
 generic-y += percpu.h
 generic-y += perfc_defn.h
 generic-y += random.h
diff --git a/xen/arch/riscv/include/asm/domain.h 
b/xen/arch/riscv/include/asm/domain.h
index e688980efa..316e7c6c84 100644
--- a/xen/arch/riscv/include/asm/domain.h
+++ b/xen/arch/riscv/include/asm/domain.h
@@ -2,6 +2,8 @@
 #ifndef ASM__RISCV__DOMAIN_H
 #define ASM__RISCV__DOMAIN_H
 
+#include <xen/mm.h>
+#include <xen/spinlock.h>
 #include <xen/xmalloc.h>
 #include <public/hvm/params.h>
 
@@ -24,11 +26,21 @@ struct arch_vcpu {
     struct vcpu_vmid vmid;
 };
 
+struct paging_domain {
+    spinlock_t lock;
+    /* Free pages from the pre-allocated pool */
+    struct page_list_head freelist;
+    /* Number of pages from the pre-allocated pool */
+    unsigned long total_pages;
+};
+
 struct arch_domain {
     struct hvm_domain hvm;
 
     /* Virtual MMU */
     struct p2m_domain p2m;
+
+    struct paging_domain paging;
 };
 
 #include <xen/sched.h>
diff --git a/xen/arch/riscv/include/asm/paging.h 
b/xen/arch/riscv/include/asm/paging.h
new file mode 100644
index 0000000000..98d8b06d45
--- /dev/null
+++ b/xen/arch/riscv/include/asm/paging.h
@@ -0,0 +1,13 @@
+#ifndef ASM_RISCV_PAGING_H
+#define ASM_RISCV_PAGING_H
+
+#include <asm-generic/paging.h>
+
+struct domain;
+
+int paging_domain_init(struct domain *d);
+
+int paging_freelist_adjust(struct domain *d, unsigned long pages,
+                           bool *preempted);
+
+#endif /* ASM_RISCV_PAGING_H */
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index 70f9e97ab6..dc0f2b2a23 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -11,6 +11,7 @@
 
 #include <asm/csr.h>
 #include <asm/flushtlb.h>
+#include <asm/paging.h>
 #include <asm/riscv_encoding.h>
 
 unsigned long __ro_after_init gstage_mode;
@@ -104,8 +105,25 @@ int p2m_init(struct domain *d)
      */
     p2m->domain = d;
 
+    paging_domain_init(d);
+
     rwlock_init(&p2m->lock);
     INIT_PAGE_LIST_HEAD(&p2m->pages);
 
     return 0;
 }
+
+/*
+ * Set the pool of pages to the required number of pages.
+ * Returns 0 for success, non-zero for failure.
+ * Call with d->arch.paging.lock held.
+ */
+int p2m_set_allocation(struct domain *d, unsigned long pages, bool *preempted)
+{
+    int rc;
+
+    if ( (rc = paging_freelist_adjust(d, pages, preempted)) )
+        return rc;
+
+    return 0;
+}
diff --git a/xen/arch/riscv/paging.c b/xen/arch/riscv/paging.c
new file mode 100644
index 0000000000..2df8de033b
--- /dev/null
+++ b/xen/arch/riscv/paging.c
@@ -0,0 +1,65 @@
+#include <xen/event.h>
+#include <xen/lib.h>
+#include <xen/mm.h>
+#include <xen/sched.h>
+#include <xen/spinlock.h>
+
+int paging_freelist_adjust(struct domain *d, unsigned long pages,
+                           bool *preempted)
+{
+    struct page_info *pg;
+
+    ASSERT(spin_is_locked(&d->arch.paging.lock));
+
+    for ( ; ; )
+    {
+        if ( d->arch.paging.total_pages < pages )
+        {
+            /* Need to allocate more memory from domheap */
+            pg = alloc_domheap_page(d, MEMF_no_owner);
+            if ( pg == NULL )
+            {
+                printk(XENLOG_ERR "Failed to allocate pages.\n");
+                return -ENOMEM;
+            }
+            ACCESS_ONCE(d->arch.paging.total_pages)++;
+            page_list_add_tail(pg, &d->arch.paging.freelist);
+        }
+        else if ( d->arch.paging.total_pages > pages )
+        {
+            /* Need to return memory to domheap */
+            pg = page_list_remove_head(&d->arch.paging.freelist);
+            if ( pg )
+            {
+                ACCESS_ONCE(d->arch.paging.total_pages)--;
+                free_domheap_page(pg);
+            }
+            else
+            {
+                printk(XENLOG_ERR
+                       "Failed to free pages, freelist is empty.\n");
+                return -ENOMEM;
+            }
+        }
+        else
+            break;
+
+        /* Check to see if we need to yield and try again */
+        if ( preempted && general_preempt_check() )
+        {
+            *preempted = true;
+            return -ERESTART;
+        }
+    }
+
+    return 0;
+}
+
+/* Domain paging struct initialization. */
+int paging_domain_init(struct domain *d)
+{
+    spin_lock_init(&d->arch.paging.lock);
+    INIT_PAGE_LIST_HEAD(&d->arch.paging.freelist);
+
+    return 0;
+}
-- 
2.51.0