Introduce arch_pmap_{un}map functions and select HAS_PMAP for CONFIG_RISCV.

Add pte_from_mfn() for use in arch_pmap_map().

Introduce flush_xen_tlb_one_local() and use it in arch_pmap_{un}map().

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
Changes in V5:
 - Add Reviewed-by: Jan Beulich <jbeulich@suse.com>.
 - Fix a typo in "Changes in V4":
   - "drop flush_xen_tlb_range_va_local() as it isn't used in this patch" ->
     "drop flush_xen_tlb_range_va() as it isn't used in this patch"
   - "s/flush_xen_tlb_range_va_local/flush_tlb_range_va_local" ->
     "s/flush_xen_tlb_one_local/flush_tlb_one_local"
---
Changes in V4:
 - mark arch_pmap_{un}map() as __init: documentation purpose and
   a necessary (but not sufficient) condition here, to validly
   use local TLB flushes only.
 - add flush_xen_tlb_one_local() to arch_pmap_map() as absense of
   "negative" TLB entrues will be guaranted only in the case
   when Svvptc extension is present.
 - s/mfn_from_pte/pte_from_mfn
 - drop mfn_to_xen_entry() as pte_from_mfn() does the same thing
 - add flags argument to pte_from_mfn().
 - update the commit message.
 - drop flush_xen_tlb_range_va() as it isn't used in this patch
 - s/flush_xen_tlb_one_local/flush_tlb_one_local
---
Changes in V3:
 - rename argument of function mfn_to_xen_entry(..., attr -> flags ).
 - update the code of mfn_to_xen_entry() to use flags argument.
 - add blank in mfn_from_pte() in return line.
 - introduce flush_xen_tlb_range_va_local() and use it inside arch_pmap_{un}map().
 - s/__ASM_PMAP_H__/ASM_PMAP_H
 - add SPDX-License-Identifier: GPL-2.0 
---
 xen/arch/riscv/Kconfig                |  1 +
 xen/arch/riscv/include/asm/flushtlb.h |  6 +++++
 xen/arch/riscv/include/asm/page.h     |  6 +++++
 xen/arch/riscv/include/asm/pmap.h     | 36 +++++++++++++++++++++++++++
 4 files changed, 49 insertions(+)
 create mode 100644 xen/arch/riscv/include/asm/pmap.h

diff --git a/xen/arch/riscv/Kconfig b/xen/arch/riscv/Kconfig
index 259eea8d3b..0112aa8778 100644
--- a/xen/arch/riscv/Kconfig
+++ b/xen/arch/riscv/Kconfig
@@ -3,6 +3,7 @@ config RISCV
 	select FUNCTION_ALIGNMENT_16B
 	select GENERIC_BUG_FRAME
 	select HAS_DEVICE_TREE
+	select HAS_PMAP
 
 config RISCV_64
 	def_bool y
diff --git a/xen/arch/riscv/include/asm/flushtlb.h b/xen/arch/riscv/include/asm/flushtlb.h
index 7ce32bea0b..f4a735fd6c 100644
--- a/xen/arch/riscv/include/asm/flushtlb.h
+++ b/xen/arch/riscv/include/asm/flushtlb.h
@@ -5,6 +5,12 @@
 #include <xen/bug.h>
 #include <xen/cpumask.h>
 
+/* Flush TLB of local processor for address va. */
+static inline void flush_tlb_one_local(vaddr_t va)
+{
+    asm volatile ( "sfence.vma %0" :: "r" (va) : "memory" );
+}
+
 /*
  * Filter the given set of CPUs, removing those that definitely flushed their
  * TLB since @page_timestamp.
diff --git a/xen/arch/riscv/include/asm/page.h b/xen/arch/riscv/include/asm/page.h
index a7419b93b2..55916eaa92 100644
--- a/xen/arch/riscv/include/asm/page.h
+++ b/xen/arch/riscv/include/asm/page.h
@@ -94,6 +94,12 @@ static inline pte_t read_pte(pte_t *p)
     return read_atomic(p);
 }
 
+static inline pte_t pte_from_mfn(mfn_t mfn, unsigned int flags)
+{
+    unsigned long pte = (mfn_x(mfn) << PTE_PPN_SHIFT) | flags;
+    return (pte_t){ .pte = pte };
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_RISCV_PAGE_H */
diff --git a/xen/arch/riscv/include/asm/pmap.h b/xen/arch/riscv/include/asm/pmap.h
new file mode 100644
index 0000000000..60065c996f
--- /dev/null
+++ b/xen/arch/riscv/include/asm/pmap.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ASM_PMAP_H
+#define ASM_PMAP_H
+
+#include <xen/bug.h>
+#include <xen/init.h>
+#include <xen/mm.h>
+#include <xen/page-size.h>
+
+#include <asm/fixmap.h>
+#include <asm/flushtlb.h>
+#include <asm/system.h>
+
+static inline void __init arch_pmap_map(unsigned int slot, mfn_t mfn)
+{
+    pte_t *entry = &xen_fixmap[slot];
+    pte_t pte;
+
+    ASSERT(!pte_is_valid(*entry));
+
+    pte = pte_from_mfn(mfn, PAGE_HYPERVISOR_RW);
+    write_pte(entry, pte);
+
+    flush_tlb_one_local(FIXMAP_ADDR(slot));
+}
+
+static inline void __init arch_pmap_unmap(unsigned int slot)
+{
+    pte_t pte = {};
+
+    write_pte(&xen_fixmap[slot], pte);
+
+    flush_tlb_one_local(FIXMAP_ADDR(slot));
+}
+
+#endif /* ASM_PMAP_H */
-- 
2.46.0