[PATCH v3] ppc: use rfid when running under a CPU from the 970 family.

[Cédric Le Goater]

A recent attempt to restrict the use of rfi on 64bit cpus in qemu
broke 32bit OpenBIOS when run under a 970.

This patches memory to replace rfi instructions with rfid in the
vector code.

Signed-off-by: Cédric Le Goater <clg(a)kaod.org>
Suggested-by: Alexander Graf <agraf(a)suse.de>
---

 Tested on qemu.

 Changes since v2 :

 - make it nicer

 arch/ppc/qemu/ofmem.c |   26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

Index: openbios.git/arch/ppc/qemu/ofmem.c
===================================================================
--- openbios.git.orig/arch/ppc/qemu/ofmem.c
+++ openbios.git/arch/ppc/qemu/ofmem.c
@@ -478,6 +478,30 @@ isi_exception(void)
     hash_page(nip, phys, mode);
 }
 
+/* When running on ppc64, we cannot use rfi anymore. Let's patch the
+ * vectors to use rfid instead.
+ */
+#define RFI     0x4c000064
+#define RFID    0x4c000024
+
+extern char __vectors[];
+extern char __vectors_end[];
+
+static void patch_rfi(void)
+{
+    uint32_t* ptr;
+    uint32_t* vec_start = (uint32_t*) 0x100UL;
+    uint32_t* vec_end = (uint32_t*) (__vectors_end - __vectors);
+
+    if (!is_ppc64())
+        return;
+
+    for (ptr = vec_start; ptr < vec_end; ptr++)  {
+        if (*ptr == RFI)
+            *ptr = RFID;
+    }
+    flush_icache_range((char*) vec_start , (char*) vec_end);
+}
 
 /************************************************************************/
 /*	init / cleanup							*/
@@ -532,6 +556,8 @@ setup_mmu(unsigned long ramsize)
 
     memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
 
+    patch_rfi();
+
     /* Enable MMU */
 
     mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Alexander Graf]

  Am 22.06.2016 um 09:29 schrieb Cédric Le Goater
<clg(a)kaod.org>rg>:
 
 A recent attempt to restrict the use of rfi on 64bit cpus in qemu
 broke 32bit OpenBIOS when run under a 970.
 
 This patches memory to replace rfi instructions with rfid in the
 vector code.
 
 Signed-off-by: Cédric Le Goater <clg(a)kaod.org>
 Suggested-by: Alexander Graf <agraf(a)suse.de>
 ---
 
 Tested on qemu.
 
 Changes since v2 :
 
 - make it nicer
 
 arch/ppc/qemu/ofmem.c |   26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 
 Index: openbios.git/arch/ppc/qemu/ofmem.c
 ===================================================================
 --- openbios.git.orig/arch/ppc/qemu/ofmem.c
 +++ openbios.git/arch/ppc/qemu/ofmem.c
 @@ -478,6 +478,30 @@ isi_exception(void)
     hash_page(nip, phys, mode);
 }
 
 +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
 + * vectors to use rfid instead.
Please use

/*
 * Comments like this
 */

and explain exactly why "we can not use rfi anymore", so that someone looking at
the code in 5 years will still know what's going on.

  + */
 +#define RFI     0x4c000064
 +#define RFID    0x4c000024
 +
 +extern char __vectors[];
 +extern char __vectors_end[];
 +
 +static void patch_rfi(void)
 +{
 +    uint32_t* ptr;
 +    uint32_t* vec_start = (uint32_t*) 0x100UL;
 +    uint32_t* vec_end = (uint32_t*) (__vectors_end - __vectors);
 +
 +    if (!is_ppc64())
 +        return;
 +
 +    for (ptr = vec_start; ptr < vec_end; ptr++)  {
Last time I asked < was not really defined for pointers. You can only match (==, !=) or
convert to numbers (uintptr_t) them. The smaller comparison might work for now, but I
can't guarantee it won't break in gcc7 or so.

In short, please just make it != :).

Alex

  +        if (*ptr == RFI)
 +            *ptr = RFID;
 +    }
 +    flush_icache_range((char*) vec_start , (char*) vec_end);
 +}
 
 /************************************************************************/
 /*    init / cleanup                            */
 @@ -532,6 +556,8 @@ setup_mmu(unsigned long ramsize)
 
     memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
 
 +    patch_rfi();
 +
     /* Enable MMU */
 
     mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Cédric Le Goater]

On 06/22/2016 09:41 AM, Alexander Graf wrote:
  
 
  Am 22.06.2016 um 09:29 schrieb Cédric Le Goater
<clg(a)kaod.org>rg>:

 A recent attempt to restrict the use of rfi on 64bit cpus in qemu
 broke 32bit OpenBIOS when run under a 970.

 This patches memory to replace rfi instructions with rfid in the
 vector code.

 Signed-off-by: Cédric Le Goater <clg(a)kaod.org>
 Suggested-by: Alexander Graf <agraf(a)suse.de>
 ---

 Tested on qemu.

 Changes since v2 :

 - make it nicer

 arch/ppc/qemu/ofmem.c |   26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

 Index: openbios.git/arch/ppc/qemu/ofmem.c
 ===================================================================
 --- openbios.git.orig/arch/ppc/qemu/ofmem.c
 +++ openbios.git/arch/ppc/qemu/ofmem.c
 @@ -478,6 +478,30 @@ isi_exception(void)
     hash_page(nip, phys, mode);
 }

 +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
 + * vectors to use rfid instead.
 
 Please use
 
 /*
  * Comments like this
  */
 
 and explain exactly why "we can not use rfi anymore", so that someone 
 looking at the code in 5 years will still know what's going on.
yep.

  + */
 +#define RFI     0x4c000064
 +#define RFID    0x4c000024
 +
 +extern char __vectors[];
 +extern char __vectors_end[];
 +
 +static void patch_rfi(void)
 +{
 +    uint32_t* ptr;
 +    uint32_t* vec_start = (uint32_t*) 0x100UL;
 +    uint32_t* vec_end = (uint32_t*) (__vectors_end - __vectors);
 +
 +    if (!is_ppc64())
 +        return;
 +
 +    for (ptr = vec_start; ptr < vec_end; ptr++)  {
 
 Last time I asked < was not really defined for pointers. You can only
 match (==, !=) or convert to numbers (uintptr_t) them. The smaller 
 comparison might work for now, but I can't guarantee it won't break 
 in gcc7 or so.
oh yes. that is true.

  In short, please just make it != :).
Thanks,

C.
 
  Alex
 
  +        if (*ptr == RFI)
 +            *ptr = RFID;
 +    }
 +    flush_icache_range((char*) vec_start , (char*) vec_end);
 +}

 /************************************************************************/
 /*    init / cleanup                            */
 @@ -532,6 +556,8 @@ setup_mmu(unsigned long ramsize)

     memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);

 +    patch_rfi();
 +
     /* Enable MMU */

     mtmsr(mfmsr() | MSR_IR | MSR_DR);