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

Thomas Huth thuth at redhat.com
Mon Jun 20 18:59:27 CEST 2016


On 20.06.2016 17:42, Cédric Le Goater wrote:
> On 06/20/2016 03:26 PM, Alexander Graf wrote:
>> On 06/20/2016 02:59 PM, Cédric Le Goater wrote:
>>> On 06/20/2016 11:49 AM, Mark Cave-Ayland wrote:
>>>> On 20/06/16 10:33, Alexander Graf wrote:
>>>>
>>>>> On 06/20/2016 11:32 AM, Cédric Le Goater wrote:
>>>>>> On 06/20/2016 09:39 AM, Alexander Graf wrote:
>>>>>>> On 20.06.16 09:34, Cédric Le Goater wrote:
>>>>>>>> A recent attempt to restrict the use of rfi to 64bit cpus in qemu
>>>>>>>> broke 32bit OpenBIOS when run under a 970.
>>>>>>>>
>>>>>>>> This is adding a dynamic check on the pvr to choose between rfi and
>>>>>>>> rfid. Only the 970 family is supported.
>>>>>>>>
>>>>>>>> Signed-off-by: Cédric Le Goater <clg at kaod.org>
>>>>>>>> ---
>>>>>>>>
>>>>>>>>    Tested on qemu.
>>>>>>>>
>>>>>>>>    arch/ppc/qemu/start.S |   25 +++++++++++++++++++++++--
>>>>>>>>    arch/ppc/start.S      |   25 +++++++++++++++++++++++--
>>>>>>>>    2 files changed, 46 insertions(+), 4 deletions(-)
>>>>>>>>
>>>>>>>> Index: openbios.git/arch/ppc/qemu/start.S
>>>>>>>> ===================================================================
>>>>>>>> --- openbios.git.orig/arch/ppc/qemu/start.S
>>>>>>>> +++ openbios.git/arch/ppc/qemu/start.S
>>>>>>>> @@ -27,6 +27,27 @@
>>>>>>>>      #ifdef CONFIG_PPC_64BITSUPPORT
>>>>>>>>    +/* When running on ppc64, we cannot use rfi anymore. Let's try to
>>>>>>>> + * catch which cpu we are running on and act accordingly. This is
>>>>>>>> + * for 970s only.
>>>>>>> Do you think you could move the check into the cpu init function and use
>>>>>>> a global variable / live patching instead? I don't remember if we need
>>>>>>> to handle any faults before we reach that path.
>>>>>> So we get an ISI really early, when returning from setup_mmu(), which is
>>>>>> the first call in _entry.
>>>>> Ok, can we add the check there?
>>>> Bear in mind that the code for entry/context switching has been reworked
>>>> pending commit whilst we switch the OpenBIOS repository over from SVN to
>>>> git. The relevant commits are here:
>>>> https://www.coreboot.org/pipermail/openbios/2016-May/009395.html.
>>>>
>>>> So please consider OpenBIOS git master plus the patchset above to be the
>>>> latest code.
>>> OK. The first version applies fine. I pushed everything here :
>>>
>>>     https://github.com/legoater/openbios/commits/master
>>>
>>> I am still looking at what Alex is asking for : a global variable doing
>>> live patching for rfi.
>>
>> It's not both - it's either or :).
> 
> ah :) I need to grow my live patching skills.
> 
>> So either you define a global variable that we can just read from to determine 
>> whether we do rfi or rfid 
> 
> That is what I started doing and that was much bigger then v1.
> 
>> or we live patch. Looking at the code, it's probably
>> easiest to live patch even. Just call a function from setup_mmu() that checks 
>> PVR and if it's 64bit, loops through (0x0 .. 0x1000) in 32bit steps and checks 
>> if *p == INST_RFI. If so, replace with INST_RFID and flush the cache.
> 
> Indeed, the hunk below seems to do the trick :
> 
> 	@@ -524,6 +524,17 @@ setup_mmu(unsigned long ramsize)
> 	         asm volatile("mtsrin %0,%1" :: "r" (sr_base + i), "r" (j));
> 	     }
> 	 
> 	+    if (is_ppc64()) {
> 	+#define RFI	0x4c000064
> 	+#define RFID	0x4c000024
> 	+        unsigned long addr;
> 	+
> 	+        for (addr = 0x2000; addr < 0x3000; addr += 4) {
> 	+            unsigned long *ptr = (unsigned long *) addr;
> 	+            if (*ptr == RFI) *ptr = RFID;

Could you please use "unsigned int" or "uint32_t" instead of unsigned
long here? ... in case anybody every tries to compile this in 64-bit mode...

 Thomas




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