roms: Flush icache when writing roms to guest memory

We use the rom infrastructure to write firmware and/or initial kernel
blobs into guest address space. So we're basically emulating the cache
off phase on very early system bootup.

That phase is usually responsible for clearing the instruction cache for
anything it writes into cachable memory, to ensure that after reboot we
don't happen to execute stale bits from the instruction cache.

So we need to invalidate the icache every time we write a rom into guest
address space. We do not need to do this for every DMA since the guest
expects it has to flush the icache manually in that case.

This fixes random reboot issues on e5500 (booke ppc) for me.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/exec.c b/exec.c
index f4b9ef25f5c5bd8c3935fa46528dd63923f4b713..896f7b83fc23fb116dd35059af148946c5bbc2ba 100644 (file)
--- a/exec.c
+++ b/exec.c
@@ -50,6 +50,7 @@
 #include "translate-all.h"
 
 #include "exec/memory-internal.h"
+#include "qemu/cache-utils.h"
 
 //#define DEBUG_SUBPAGE
 
@@ -2010,9 +2011,13 @@ void cpu_physical_memory_rw(hwaddr addr, uint8_t *buf,
     address_space_rw(&address_space_memory, addr, buf, len, is_write);
 }
 
-/* used for ROM loading : can write in RAM and ROM */
-void cpu_physical_memory_write_rom(hwaddr addr,
-                                   const uint8_t *buf, int len)
+enum write_rom_type {
+    WRITE_DATA,
+    FLUSH_CACHE,
+};
+
+static inline void cpu_physical_memory_write_rom_internal(
+    hwaddr addr, const uint8_t *buf, int len, enum write_rom_type type)
 {
     hwaddr l;
     uint8_t *ptr;
@@ -2031,8 +2036,15 @@ void cpu_physical_memory_write_rom(hwaddr addr,
             addr1 += memory_region_get_ram_addr(mr);
             /* ROM/RAM case */
             ptr = qemu_get_ram_ptr(addr1);
-            memcpy(ptr, buf, l);
-            invalidate_and_set_dirty(addr1, l);
+            switch (type) {
+            case WRITE_DATA:
+                memcpy(ptr, buf, l);
+                invalidate_and_set_dirty(addr1, l);
+                break;
+            case FLUSH_CACHE:
+                flush_icache_range((uintptr_t)ptr, (uintptr_t)ptr + l);
+                break;
+            }
         }
         len -= l;
         buf += l;
@@ -2040,6 +2052,28 @@ void cpu_physical_memory_write_rom(hwaddr addr,
     }
 }
 
+/* used for ROM loading : can write in RAM and ROM */
+void cpu_physical_memory_write_rom(hwaddr addr,
+                                   const uint8_t *buf, int len)
+{
+    cpu_physical_memory_write_rom_internal(addr, buf, len, WRITE_DATA);
+}
+
+void cpu_flush_icache_range(hwaddr start, int len)
+{
+    /*
+     * This function should do the same thing as an icache flush that was
+     * triggered from within the guest. For TCG we are always cache coherent,
+     * so there is no need to flush anything. For KVM / Xen we need to flush
+     * the host's instruction cache at least.
+     */
+    if (tcg_enabled()) {
+        return;
+    }
+
+    cpu_physical_memory_write_rom_internal(start, NULL, len, FLUSH_CACHE);
+}
+
 typedef struct {
     MemoryRegion *mr;
     void *buffer;

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 60d2ebd4ac85d98079fd65cf3d5d955709ca02f3..0634bee20c9394ce871f7f354eaf66aaa59959f4 100644 (file)
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -785,6 +785,13 @@ static void rom_reset(void *unused)
             g_free(rom->data);
             rom->data = NULL;
         }
+        /*
+         * The rom loader is really on the same level as firmware in the guest
+         * shadowing a ROM into RAM. Such a shadowing mechanism needs to ensure
+         * that the instruction cache for that new region is clear, so that the
+         * CPU definitely fetches its instructions from the just written data.
+         */
+        cpu_flush_icache_range(rom->addr, rom->datasize);
     }
 }
 

diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index e4996e19c322d145d8fbf532f4c0d7ef39c79f24..8f33122c9f15937f58e5941b3465a0572334f77b 100644 (file)
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -110,6 +110,7 @@ void stq_phys(hwaddr addr, uint64_t val);
 
 void cpu_physical_memory_write_rom(hwaddr addr,
                                    const uint8_t *buf, int len);
+void cpu_flush_icache_range(hwaddr start, int len);
 
 extern struct MemoryRegion io_mem_rom;
 extern struct MemoryRegion io_mem_notdirty;