[PATCH v8 3/3] hw/riscv: clear kernel_entry higher bits in load_elf_ram_sym()

[Daniel Henrique Barboza]

Recent hw/risc/boot.c changes caused a regression in an use case with
the Xvisor hypervisor. Running a 32 bit QEMU guest with '-kernel'
stopped working. The reason seems to be that Xvisor is using 64 bit to
encode the 32 bit addresses from the guest, and load_elf_ram_sym() is
sign-extending the result with '1's [1].

Use a translate_fn() callback to be called by load_elf_ram_sym() and
return only the 32 bits address if we're running a 32 bit CPU.

[1] https://lists.gnu.org/archive/html/qemu-devel/2023-01/msg02281.html

Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Suggested-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 hw/riscv/boot.c            | 20 +++++++++++++++++++-
 hw/riscv/microchip_pfsoc.c |  4 ++--
 hw/riscv/opentitan.c       |  3 ++-
 hw/riscv/sifive_e.c        |  3 ++-
 hw/riscv/sifive_u.c        |  4 ++--
 hw/riscv/spike.c           |  2 +-
 hw/riscv/virt.c            |  4 ++--
 include/hw/riscv/boot.h    |  1 +
 target/riscv/cpu_bits.h    |  1 +
 9 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
index e868fb6ade..0fd39df7f3 100644
--- a/hw/riscv/boot.c
+++ b/hw/riscv/boot.c
@@ -213,7 +213,24 @@ static void riscv_load_initrd(MachineState *machine, 
uint64_t kernel_entry)
     }
 }
 
+static uint64_t translate_kernel_address(void *opaque, uint64_t addr)
+{
+    RISCVHartArrayState *harts = opaque;
+
+    /*
+     * For 32 bit CPUs, kernel_load_base is sign-extended (i.e.
+     * it can be padded with '1's) if the hypervisor is using
+     * 64 bit addresses with 32 bit guests.
+     */
+    if (riscv_is_32bit(harts)) {
+        return extract64(addr, 0, RV32_KERNEL_ADDR_LEN);
+    }
+
+    return addr;
+}
+
 target_ulong riscv_load_kernel(MachineState *machine,
+                               RISCVHartArrayState *harts,
                                target_ulong kernel_start_addr,
                                bool load_initrd,
                                symbol_fn_t sym_cb)
@@ -231,7 +248,8 @@ target_ulong riscv_load_kernel(MachineState *machine,
      * the (expected) load address load address. This allows kernels to have
      * separate SBI and ELF entry points (used by FreeBSD, for example).
      */
-    if (load_elf_ram_sym(kernel_filename, NULL, NULL, NULL,
+    if (load_elf_ram_sym(kernel_filename, NULL,
+                         translate_kernel_address, NULL,
                          NULL, &kernel_load_base, NULL, NULL, 0,
                          EM_RISCV, 1, 0, NULL, true, sym_cb) > 0) {
         kernel_entry = kernel_load_base;
diff --git a/hw/riscv/microchip_pfsoc.c b/hw/riscv/microchip_pfsoc.c
index c45023a2b1..b7e171b605 100644
--- a/hw/riscv/microchip_pfsoc.c
+++ b/hw/riscv/microchip_pfsoc.c
@@ -629,8 +629,8 @@ static void microchip_icicle_kit_machine_init(MachineState 
*machine)
         kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc.u_cpus,
                                                          firmware_end_addr);
 
-        kernel_entry = riscv_load_kernel(machine, kernel_start_addr,
-                                         true, NULL);
+        kernel_entry = riscv_load_kernel(machine, &s->soc.u_cpus,
+                                         kernel_start_addr, true, NULL);
 
         /* Compute the fdt load address in dram */
         fdt_load_addr = riscv_load_fdt(memmap[MICROCHIP_PFSOC_DRAM_LO].base,
diff --git a/hw/riscv/opentitan.c b/hw/riscv/opentitan.c
index f6fd9725a5..1404a52da0 100644
--- a/hw/riscv/opentitan.c
+++ b/hw/riscv/opentitan.c
@@ -101,7 +101,8 @@ static void opentitan_board_init(MachineState *machine)
     }
 
     if (machine->kernel_filename) {
-        riscv_load_kernel(machine, memmap[IBEX_DEV_RAM].base, false, NULL);
+        riscv_load_kernel(machine, &s->soc.cpus,
+                          memmap[IBEX_DEV_RAM].base, false, NULL);
     }
 }
 
diff --git a/hw/riscv/sifive_e.c b/hw/riscv/sifive_e.c
index 6835d1c807..04939b60c3 100644
--- a/hw/riscv/sifive_e.c
+++ b/hw/riscv/sifive_e.c
@@ -114,7 +114,8 @@ static void sifive_e_machine_init(MachineState *machine)
                           memmap[SIFIVE_E_DEV_MROM].base, 
&address_space_memory);
 
     if (machine->kernel_filename) {
-        riscv_load_kernel(machine, memmap[SIFIVE_E_DEV_DTIM].base,
+        riscv_load_kernel(machine, &s->soc.cpus,
+                          memmap[SIFIVE_E_DEV_DTIM].base,
                           false, NULL);
     }
 }
diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
index ccad386920..b0b3e6f03a 100644
--- a/hw/riscv/sifive_u.c
+++ b/hw/riscv/sifive_u.c
@@ -598,8 +598,8 @@ static void sifive_u_machine_init(MachineState *machine)
         kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc.u_cpus,
                                                          firmware_end_addr);
 
-        kernel_entry = riscv_load_kernel(machine, kernel_start_addr,
-                                         true, NULL);
+        kernel_entry = riscv_load_kernel(machine, &s->soc.u_cpus,
+                                         kernel_start_addr, true, NULL);
     } else {
        /*
         * If dynamic firmware is used, it doesn't know where is the next mode
diff --git a/hw/riscv/spike.c b/hw/riscv/spike.c
index 91bf194ec1..3c0ac916c0 100644
--- a/hw/riscv/spike.c
+++ b/hw/riscv/spike.c
@@ -305,7 +305,7 @@ static void spike_board_init(MachineState *machine)
         kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc[0],
                                                          firmware_end_addr);
 
-        kernel_entry = riscv_load_kernel(machine, kernel_start_addr,
+        kernel_entry = riscv_load_kernel(machine, &s->soc[0], 
kernel_start_addr,
                                          true, htif_symbol_callback);
     } else {
        /*
diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index e374b58f89..cf64da65bf 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -1281,8 +1281,8 @@ static void virt_machine_done(Notifier *notifier, void 
*data)
         kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc[0],
                                                          firmware_end_addr);
 
-        kernel_entry = riscv_load_kernel(machine, kernel_start_addr,
-                                         true, NULL);
+        kernel_entry = riscv_load_kernel(machine, &s->soc[0],
+                                         kernel_start_addr, true, NULL);
     } else {
        /*
         * If dynamic firmware is used, it doesn't know where is the next mode
diff --git a/include/hw/riscv/boot.h b/include/hw/riscv/boot.h
index cbd131bad7..bc9faed397 100644
--- a/include/hw/riscv/boot.h
+++ b/include/hw/riscv/boot.h
@@ -44,6 +44,7 @@ target_ulong riscv_load_firmware(const char 
*firmware_filename,
                                  hwaddr firmware_load_addr,
                                  symbol_fn_t sym_cb);
 target_ulong riscv_load_kernel(MachineState *machine,
+                               RISCVHartArrayState *harts,
                                target_ulong firmware_end_addr,
                                bool load_initrd,
                                symbol_fn_t sym_cb);
diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index 8b0d7e20ea..8fcaeae342 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -751,6 +751,7 @@ typedef enum RISCVException {
 #define MENVCFG_STCE                       (1ULL << 63)
 
 /* For RV32 */
+#define RV32_KERNEL_ADDR_LEN               32
 #define MENVCFGH_PBMTE                     BIT(30)
 #define MENVCFGH_STCE                      BIT(31)
 
-- 
2.39.0