Re: [Qemu-devel] [Qemu-ppc] [PATCH 4/5] target-ppc: Handle ibm, nmi-register RTAS call

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

On Monday 08 September 2014 02:17 AM, Alexander Graf wrote:
> 
> 
> On 25.08.14 15:45, Aravinda Prasad wrote:
>> This patch adds FWNMI support in qemu for powerKVM
>> guests by handling the ibm,nmi-register rtas call.
>> Whenever OS issues ibm,nmi-register RTAS call, the
>> machine check notification address is saved and the
>> machine check interrupt vector 0x200 is patched to
>> issue a private hcall.
>>
>> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
>> ---
>>  hw/ppc/spapr_rtas.c    |   91 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/hw/ppc/spapr.h |    8 ++++
>>  2 files changed, 98 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
>> index 02ddbf9..1135d2b 100644
>> --- a/hw/ppc/spapr_rtas.c
>> +++ b/hw/ppc/spapr_rtas.c
>> @@ -277,6 +277,91 @@ static void rtas_ibm_set_system_parameter(PowerPCCPU *cpu,
>>      rtas_st(rets, 0, ret);
>>  }
>>  
>> +static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
>> +                                  sPAPREnvironment *spapr,
>> +                                  uint32_t token, uint32_t nargs,
>> +                                  target_ulong args,
>> +                                  uint32_t nret, target_ulong rets)
>> +{
>> +    int i;
>> +    uint32_t branch_inst = 0x48000002;
>> +    target_ulong guest_machine_check_addr;
>> +    PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
>> +    /*
>> +     * Trampoline saves r3 in sprg2 and issues private hcall
>> +     * to request qemu to build error log. QEMU builds the
>> +     * error log, copies to rtas-blob and returns the address.
>> +     * The initial 16 bytes in rtas-blob consists of saved srr0
>> +     * and srr1 which we restore and pass on the actual error
>> +     * log address to OS handled mcachine check notification
>> +     * routine
>> +     */
>> +    uint32_t trampoline[] = {
>> +        0x7c7243a6,    /* mtspr   SPRN_SPRG2,r3 */
>> +        0x38600000,    /* li      r3,0   */
>> +        /* 0xf004 is the KVMPPC_H_REPORT_ERR private HCALL */
>> +        0x6063f004,    /* ori     r3,r3,f004  */
>> +        /* Issue H_CALL */
>> +        0x44000022,    /*  sc      1     */
>> +        0x7c9243a6,    /* mtspr r4 sprg2 */
>> +        0xe8830000,    /* ld r4, 0(r3) */
>> +        0x7c9a03a6,    /* mtspr r4, srr0 */
>> +        0xe8830008,    /* ld r4, 8(r3) */
>> +        0x7c9b03a6,    /* mtspr r4, srr1 */
>> +        0x38630010,    /* addi r3,r3,16 */
>> +        0x7c9242a6,    /* mfspr r4 sprg2 */
>> +        0x48000002,    /* Branch to address registered
>> +                        * by OS. The branch address is
>> +                        * patched below */
>> +        0x48000000,    /* b . */
> 
> So how about we just completely change the layout of the RTAS blob?
> 
> Imagine something like the following (completely untested):
> 
> ----
> 
> /**** index table ****/
> .long rtas_entry
> .long nmi_register
> .long nmi_register_final_branch
> .long nmi_data
> 
> /**** RTAS handling code ****/
> .align 1024
> rtas_entry:
> 	...
> nmi_register:
> 	...
> nmi_register_final_branch:
> 	ba .
> 
> /**** RTAS data regions ****/
> .align 4096
> nmi_data:
> .long 0
> .align 4096
> 
> ----
> 
> With this we should be able to have a nice hybrid between easily tunable
> asm code and an easy to load and handle blob.

Sorry, I was out of office hence could not respond.

Yes, even I prefer something like this.

BTB, did you intend to have this in spapr-rtas.S? The spapr-rtas.S is
compiled into a binary and is read into spapr->rtas_blob. If we want to
have rtas-blob layout something similar to above then we may need to
link the object file of spapr-rtas.S to QEMU so that the symbols in
"index table" and other places could be resolved inside QEMU.

If this is fine I will include it in v3.

Regards,
Aravinda

> 
> 
> Alex
> 

-- 
Regards,
Aravinda