xen/riscv: introduce asm/pmap.h header

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>

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
 	select HAS_VMAP
 
 config RISCV_64

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.

xen/arch/riscv/include/asm/page.h

@@ -94,6 +94,12 @@ static inline pte_t read_pte(const 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 */

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 */