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

[Alexander Graf <agraf@suse.de>]

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.


Alex