Introduce the following things:
- Update p2m_domain structure, which describe per p2m-table state, with:
  - lock to protect updates to p2m.
  - pool with pages used to construct p2m.
  - back pointer to domain structure.
- p2m_init() to initalize members introduced in p2m_domain structure.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
Changes in V5:
 - Acked-by: Jan Beulich <jbeulich@suse.com>.
---
Changes in V4:
 - Move an introduction of clean_pte member of p2m_domain structure to the
   patch where it is started to be used:
     xen/riscv: add root page table allocation
 - Add prototype of p2m_init() to asm/p2m.h.
---
Changes in V3:
 - s/p2m_type/p2m_types.
 - Drop init. of p2m->clean_pte in p2m_init() as CONFIG_HAS_PASSTHROUGH is
   going to be selected unconditionaly. Plus CONFIG_HAS_PASSTHROUGH isn't
   ready to be used for RISC-V.
   Add compilation error to not forget to init p2m->clean_pte.
 - Move defintion of p2m->domain up in p2m_init().
 - Add iommu_use_hap_pt() when p2m->clean_pte is initialized.
 - Add the comment above p2m_types member of p2m_domain struct.
 - Add need_flush member to p2m_domain structure.
 - Move introduction of p2m_write_(un)lock() and p2m_tlb_flush_sync()
   to the patch where they are really used:
     xen/riscv: implement guest_physmap_add_entry() for mapping GFNs to MFN
 - Add p2m member to arch_domain structure.
 - Drop p2m_types from struct p2m_domain as P2M type for PTE will be stored
   differently.
 - Drop default_access as it isn't going to be used for now.
 - Move defintion of p2m_is_write_locked() to "implement function to map memory
   in guest p2m"  where it is really used.
---
Changes in V2:
 - Use introduced erlier sbi_remote_hfence_gvma_vmid() for proper implementation
   of p2m_force_tlb_flush_sync() as TLB flushing needs to happen for each pCPU
   which potentially has cached a mapping, what is tracked by d->dirty_cpumask.
 - Drop unnecessary blanks.
 - Fix code style for # of pre-processor directive.
 - Drop max_mapped_gfn and lowest_mapped_gfn as they aren't used now.
 - [p2m_init()] Set p2m->clean_pte=false if CONFIG_HAS_PASSTHROUGH=n.
 - [p2m_init()] Update the comment above p2m->domain = d;
 - Drop p2m->need_flush as it seems to be always true for RISC-V and as a
   consequence drop p2m_tlb_flush_sync().
 - Move to separate patch an introduction of root page table allocation.
---
 xen/arch/riscv/include/asm/domain.h |  5 +++++
 xen/arch/riscv/include/asm/p2m.h    | 33 +++++++++++++++++++++++++++++
 xen/arch/riscv/p2m.c                | 20 +++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/xen/arch/riscv/include/asm/domain.h b/xen/arch/riscv/include/asm/domain.h
index aac1040658..e688980efa 100644
--- a/xen/arch/riscv/include/asm/domain.h
+++ b/xen/arch/riscv/include/asm/domain.h
@@ -5,6 +5,8 @@
 #include <xen/xmalloc.h>
 #include <public/hvm/params.h>
 
+#include <asm/p2m.h>
+
 struct vcpu_vmid {
     uint64_t generation;
     uint16_t vmid;
@@ -24,6 +26,9 @@ struct arch_vcpu {
 
 struct arch_domain {
     struct hvm_domain hvm;
+
+    /* Virtual MMU */
+    struct p2m_domain p2m;
 };
 
 #include <xen/sched.h>
diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/p2m.h
index 3a5066f360..a129ed8392 100644
--- a/xen/arch/riscv/include/asm/p2m.h
+++ b/xen/arch/riscv/include/asm/p2m.h
@@ -3,6 +3,9 @@
 #define ASM__RISCV__P2M_H
 
 #include <xen/errno.h>
+#include <xen/mm.h>
+#include <xen/rwlock.h>
+#include <xen/types.h>
 
 #include <asm/page-bits.h>
 
@@ -10,6 +13,34 @@ extern unsigned char gstage_mode;
 
 #define paddr_bits PADDR_BITS
 
+/* Get host p2m table */
+#define p2m_get_hostp2m(d) (&(d)->arch.p2m)
+
+/* Per-p2m-table state */
+struct p2m_domain {
+    /*
+     * Lock that protects updates to the p2m.
+     */
+    rwlock_t lock;
+
+    /* Pages used to construct the p2m */
+    struct page_list_head pages;
+
+    /* Back pointer to domain */
+    struct domain *domain;
+
+    /*
+     * P2M updates may required TLBs to be flushed (invalidated).
+     *
+     * Flushes may be deferred by setting 'need_flush' and then flushing
+     * when the p2m write lock is released.
+     *
+     * If an immediate flush is required (e.g, if a super page is
+     * shattered), call p2m_tlb_flush_sync().
+     */
+    bool need_flush;
+};
+
 /*
  * List of possible type for each page in the p2m entry.
  * The number of available bit per page in the pte for this purpose is 2 bits.
@@ -92,6 +123,8 @@ static inline bool arch_acquire_resource_check(struct domain *d)
 
 void pre_gstage_init(void);
 
+int p2m_init(struct domain *d);
+
 #endif /* ASM__RISCV__P2M_H */
 
 /*
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index d8027a270f..1b5fc7ffff 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -3,6 +3,10 @@
 #include <xen/init.h>
 #include <xen/lib.h>
 #include <xen/macros.h>
+#include <xen/mm.h>
+#include <xen/paging.h>
+#include <xen/rwlock.h>
+#include <xen/sched.h>
 #include <xen/sections.h>
 
 #include <asm/csr.h>
@@ -97,3 +101,19 @@ void __init pre_gstage_init(void)
 
     vmid_init();
 }
+
+int p2m_init(struct domain *d)
+{
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+
+    /*
+     * "Trivial" initialisation is now complete.  Set the backpointer so the
+     * users of p2m could get an access to domain structure.
+     */
+    p2m->domain = d;
+
+    rwlock_init(&p2m->lock);
+    INIT_PAGE_LIST_HEAD(&p2m->pages);
+
+    return 0;
+}
-- 
2.51.0