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

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

On Tuesday 26 August 2014 11:32 AM, David Gibson wrote:
> On Mon, Aug 25, 2014 at 07:15:45PM +0530, 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 */
> 
> You should construct the instruction from the KVMPPC_H_REPORT_ERR
> constant, otherwise it's an undocumented magic dependency between
> parts of the code.

hmm.. yes. will do

> 
>> +        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 . */
>> +    };
>> +    int total_inst = sizeof(trampoline) / sizeof(uint32_t);
>> +
>> +    /* Store the system reset and machine check address */
>> +    guest_machine_check_addr = rtas_ld(args, 1);
>> +
>> +    /* Safety Check */
>> +    if (sizeof(trampoline) >= MC_INTERRUPT_VECTOR_SIZE) {
>> +        fprintf(stderr, "Unable to register ibm,nmi_register: "
>> +                "Trampoline size exceeded\n");
>> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
>> +        return;
> 
> The guest has absolutely no influence over this, so this should be an
> assert() rather than returning an rtas error.  Or better yet, detect
> the failure at compile time, since it doesn't depend on anything
> runtime either.

yes better to detect at compile time.

> 
>> +    }
>> +
>> +    /*
>> +     * Update the branch instruction in trampoline with the absolute
>> +     * machine check address requested by OS
>> +     */
>> +    branch_inst |= guest_machine_check_addr;
> 
> Surely there should be some sanity checking of the address here, or it
> can clobber any part of that branch instruction.

Will include a check to make sure instruction opcode is not clobbered.

> 
>> +    memcpy(&trampoline[11], &branch_inst, sizeof(branch_inst));
>> +
>> +    /* Handle all Host/Guest LE/BE combinations */
>> +    if ((*pcc->interrupts_big_endian)(cpu)) {
>> +        for (i = 0; i < total_inst; i++) {
>> +            trampoline[i] = cpu_to_be32(trampoline[i]);
>> +        }
>> +    } else {
>> +        for (i = 0; i < total_inst; i++) {
>> +            trampoline[i] = cpu_to_le32(trampoline[i]);
>> +        }
>> +    }
>> +
>> +    /* Patch 0x200 NMI interrupt vector memory area of guest */
>> +    cpu_physical_memory_write(MC_INTERRUPT_VECTOR, trampoline,
>> +                              sizeof(trampoline));
>> +
>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> +}
>> +
>> +static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
>> +                                   sPAPREnvironment *spapr,
>> +                                   uint32_t token, uint32_t nargs,
>> +                                   target_ulong args,
>> +                                   uint32_t nret, target_ulong rets)
>> +{
>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> +}
>> +
> 
> This nmi_interlock call isn't described in the commit message.

Yes. will include

Regards,
Aravinda

> 

-- 
Regards,
Aravinda