Introduce copy_to_guest_phys() for RISC-V, based on the Arm implementation.

Add a generic copy_guest() helper for copying to and from guest physical
(and potentially virtual addresses in the future), and implement
translate_get_page() to translate a guest physical address into a struct
page_info via the domain p2m.

Compared to the Arm code:
- Drop COPY_flush_dcache(), as no such use cases exist on RISC-V.
- Do not implement the linear mapping case, which is currently unused.
- Use PAGE_OFFSET() to initialize the local offset variable in copy_guest().

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
Changes in v2:
 - Use BIT() instead of open-coding.
 - Rename COPY_ipa to COPY_gpa.
 - Rename COPY_linear to COPY_gva.
 - Use  BUG_ON(linear) instead if (lineer) + BUG_ON.
 - Rename arg liner to gva for translate_get_page().
 - Update translate_get_page() to properly handling write argument.
 - Return unsigned int for copy_guest() and copy_to_guest_phys() as
   len function parameter is only 'unsigned int'.
 - Reformat function arguments for alignment
---
 xen/arch/riscv/Makefile                   |   1 +
 xen/arch/riscv/guestcopy.c                | 116 ++++++++++++++++++++++
 xen/arch/riscv/include/asm/guest_access.h |   7 ++
 3 files changed, 124 insertions(+)
 create mode 100644 xen/arch/riscv/guestcopy.c

diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index 6b3f3ed90bdb..6d3c822409b8 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -4,6 +4,7 @@ obj-y += domain.o
 obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
 obj-y += entry.o
 obj-$(CONFIG_HAS_EX_TABLE) += extables.o
+obj-y += guestcopy.o
 obj-y += imsic.o
 obj-y += intc.o
 obj-y += irq.o
diff --git a/xen/arch/riscv/guestcopy.c b/xen/arch/riscv/guestcopy.c
new file mode 100644
index 000000000000..d774a90bff92
--- /dev/null
+++ b/xen/arch/riscv/guestcopy.c
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <xen/domain_page.h>
+#include <xen/page-size.h>
+#include <xen/sched.h>
+#include <xen/string.h>
+
+#include <asm/guest_access.h>
+
+#define COPY_from_guest     0U
+#define COPY_to_guest       BIT(0, U)
+#define COPY_gpa            0U
+#define COPY_gva            BIT(1, U)
+
+typedef union
+{
+    struct
+    {
+        struct vcpu *v;
+    } gva;
+
+    struct
+    {
+        struct domain *d;
+    } gpa;
+} copy_info_t;
+
+#define GVA_INFO(vcpu) ((copy_info_t) { .gva = { vcpu } })
+#define GPA_INFO(domain) ((copy_info_t) { .gpa = { domain } })
+
+static struct page_info *translate_get_page(copy_info_t info, uint64_t addr,
+                                            bool gva, bool write)
+{
+    p2m_type_t p2mt;
+    struct page_info *page;
+
+    /*
+     * Not implemented yet.
+     *
+     * If gva == true, the operation will likely require a struct vcpu
+     * rather than just a struct domain. For this reason copy_info_t is
+     * already passed here instead of only struct domain.
+     */
+    BUG_ON(gva);
+
+    page = get_page_from_gfn(info.gpa.d, paddr_to_pfn(addr), &p2mt, P2M_ALLOC);
+
+    if ( !page )
+        return NULL;
+
+    if ( write ? p2mt != p2m_ram_rw : !p2m_is_ram(p2mt) )
+    {
+        put_page(page);
+        return NULL;
+    }
+
+    return page;
+}
+
+static unsigned int copy_guest(void *buf, uint64_t addr, unsigned int len,
+                               copy_info_t info, unsigned int flags)
+{
+    unsigned int offset = PAGE_OFFSET(addr);
+
+    BUILD_BUG_ON((sizeof(addr)) < sizeof(vaddr_t));
+    BUILD_BUG_ON((sizeof(addr)) < sizeof(paddr_t));
+
+    while ( len )
+    {
+        void *p;
+        unsigned int size = min(len, (unsigned int)PAGE_SIZE - offset);
+        struct page_info *page;
+
+        page = translate_get_page(info, addr, flags & COPY_gva,
+                                  flags & COPY_to_guest);
+        if ( page == NULL )
+            return len;
+
+        p = __map_domain_page(page);
+        p += offset;
+        if ( flags & COPY_to_guest )
+        {
+            /*
+             * buf will be NULL when the caller request to zero the
+             * guest memory.
+             */
+            if ( buf )
+                memcpy(p, buf, size);
+            else
+                memset(p, 0, size);
+        }
+        else
+            memcpy(buf, p, size);
+
+        unmap_domain_page(p - offset);
+        put_page(page);
+        len -= size;
+        buf += size;
+        addr += size;
+
+        /*
+         * After the first iteration, guest virtual address is correctly
+         * aligned to PAGE_SIZE.
+         */
+        offset = 0;
+    }
+
+    return 0;
+}
+
+unsigned int copy_to_guest_phys(struct domain *d, paddr_t gpa, void *buf,
+                                unsigned int len)
+{
+    return copy_guest(buf, gpa, len, GPA_INFO(d),
+                      COPY_to_guest | COPY_gpa);
+}
diff --git a/xen/arch/riscv/include/asm/guest_access.h b/xen/arch/riscv/include/asm/guest_access.h
index 3f4c68e4da20..f0a42745330e 100644
--- a/xen/arch/riscv/include/asm/guest_access.h
+++ b/xen/arch/riscv/include/asm/guest_access.h
@@ -2,6 +2,10 @@
 #ifndef ASM__RISCV__GUEST_ACCESS_H
 #define ASM__RISCV__GUEST_ACCESS_H
 
+#include <xen/types.h>
+
+struct domain;
+
 unsigned int raw_copy_to_guest(void *to, const void *from, unsigned len);
 unsigned int raw_copy_from_guest(void *to, const void *from, unsigned len);
 unsigned int raw_clear_guest(void *to, unsigned int len);
@@ -18,6 +22,9 @@ unsigned int raw_clear_guest(void *to, unsigned int len);
 #define guest_handle_okay(hnd, nr) (1)
 #define guest_handle_subrange_okay(hnd, first, last) (1)
 
+unsigned int copy_to_guest_phys(struct domain *d, paddr_t gpa, void *buf,
+                                unsigned int len);
+
 #endif /* ASM__RISCV__GUEST_ACCESS_H */
 /*
  * Local variables:
-- 
2.53.0