[PATCH v1 2/6] xen/riscv: implement copy_to_guest_phys()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

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@xxxxxxxxx>
---
 xen/arch/riscv/Makefile                   |   1 +
 xen/arch/riscv/guestcopy.c                | 112 ++++++++++++++++++++++
 xen/arch/riscv/include/asm/guest_access.h |   7 ++
 3 files changed, 120 insertions(+)
 create mode 100644 xen/arch/riscv/guestcopy.c

diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index 7439d029cc45..90210799e038 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -3,6 +3,7 @@ obj-y += cpufeature.o
 obj-y += domain.o
 obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
 obj-y += entry.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..19b681c30b1b
--- /dev/null
+++ b/xen/arch/riscv/guestcopy.c
@@ -0,0 +1,112 @@
+/* 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 << 0)
+#define COPY_to_guest       (1U << 0)
+#define COPY_ipa            (0U << 1)
+#define COPY_linear         (1U << 1)
+
+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 linear, bool write)
+{
+    p2m_type_t p2mt;
+    struct page_info *page;
+
+    if ( linear )
+        BUG_ON("unimplemeted\n");
+
+    page = get_page_from_gfn(info.gpa.d, paddr_to_pfn(addr), &p2mt, P2M_ALLOC);
+
+    if ( !page )
+        return NULL;
+
+    if ( !p2m_is_ram(p2mt) )
+    {
+        put_page(page);
+        return NULL;
+    }
+
+    return page;
+}
+
+static unsigned long 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_linear,
+                                  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 long 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_ipa);
+}
diff --git a/xen/arch/riscv/include/asm/guest_access.h 
b/xen/arch/riscv/include/asm/guest_access.h
index 7cd51fbbdead..024e29b4c9f9 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 long raw_copy_to_guest(void *to, const void *from, unsigned len);
 unsigned long raw_copy_from_guest(void *to, const void *from, unsigned len);
 unsigned long raw_clear_guest(void *to, unsigned int len);
@@ -18,6 +22,9 @@ unsigned long 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 long copy_to_guest_phys(struct domain *d, paddr_t gpa, void *buf,
+                                 unsigned int len);
+
 #endif /* ASM__RISCV__GUEST_ACCESS_H */
 /*
  * Local variables:
-- 
2.52.0