Re: [Qemu-devel] [PATCH v13 2/3] sPAPR: Implement EEH RTAS calls

[Alexander Graf <agraf@suse.de>]

On 16.12.14 00:08, Gavin Shan wrote:
> On Mon, Dec 15, 2014 at 03:52:17PM +0100, Alexander Graf wrote:
>> On 15.12.14 01:15, Gavin Shan wrote:
>>> The emulation for EEH RTAS requests from guest isn't covered
>>> by QEMU yet and the patch implements them.
>>>
>>> The patch defines constants used by EEH RTAS calls and adds
>>> callback sPAPRPHBClass::eeh_handler, which is going to be used
>>> this way:
>>>
>>>   * RTAS calls are received in spapr_pci.c, sanity check is done
>>>     there.
>>>   * RTAS handlers handle what they can. If there is something it
>>>     cannot handle and sPAPRPHBClass::eeh_handler callback is defined,
>>>     it is called.
>>>   * sPAPRPHBClass::eeh_handler is only implemented for VFIO now. It
>>>     does ioctl() to the IOMMU container fd to complete the call. Error
>>>     codes from that ioctl() are transferred back to the guest.
>>>
>>> [aik: defined RTAS tokens for EEH RTAS calls]
>>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>>> ---
>>>  hw/ppc/spapr_pci.c          | 246 ++++++++++++++++++++++++++++++++++++++++++++
>>>  include/hw/pci-host/spapr.h |   7 ++
>>>  include/hw/ppc/spapr.h      |  43 +++++++-
>>>  3 files changed, 294 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
>>> index 3d70efe..3bb1971 100644
>>> --- a/hw/ppc/spapr_pci.c
>>> +++ b/hw/ppc/spapr_pci.c
>>> @@ -406,6 +406,233 @@ static void rtas_ibm_query_interrupt_source_number(PowerPCCPU *cpu,
>>>      rtas_st(rets, 2, 1);/* 0 == level; 1 == edge */
>>>  }
>>>  
>>> +static int rtas_handle_eeh_request(sPAPREnvironment *spapr,
>>> +                                   uint64_t buid, uint32_t req, uint32_t opt)
>>> +{
>>> +    sPAPRPHBState *sphb = spapr_pci_find_phb(spapr, buid);
>>> +    sPAPRPHBClass *info = SPAPR_PCI_HOST_BRIDGE_GET_CLASS(sphb);
>>
>> What happens when you try to cast NULL? Could a guest process invoke a
>> host assert() through this and abort the whole VM?
>>
> 
> Yes, it would cause core dump. I had one experiment to force assigning
> NULL to "sphb" before doing the cast, the whole VM is aborted. So I
> guess you're happy to have something as follows. If you're not suggesting
> something else, I'll update the code as follows in next version:
> 
> 	sPAPRPHBState *sphb = spapr_pci_find_phb(spapr, buid);
> 	sPAPRPHBClass *info;
> 
> 	if (!sphb) {
> 	    return -ENODEV;
> 	}
> 
> 	info = SPAPR_PCI_HOST_BRIDGE_GET_CLASS(sphb);
> 	if (!info->eeh_handler) {
> 	    return -ENOENT;
> 	}
> 
> 	return info->eeh_handler(sphb, req, opt);

Yes, I think this is a lot safer. And yes, the other patch looks sane to me.

> 
>>> +
>>> +    if (!sphb || !info->eeh_handler) {
>>> +        return -ENOENT;
>>> +    }
>>> +
>>> +    return info->eeh_handler(sphb, req, opt);
>>> +}
>>> +
>>> +static void rtas_ibm_set_eeh_option(PowerPCCPU *cpu,
>>> +                                    sPAPREnvironment *spapr,
>>> +                                    uint32_t token, uint32_t nargs,
>>> +                                    target_ulong args, uint32_t nret,
>>> +                                    target_ulong rets)
>>> +{
>>> +    uint32_t addr, option;
>>> +    uint64_t buid = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 2);
>>> +    int ret;
>>> +
>>> +    if ((nargs != 4) || (nret != 1)) {
>>> +        goto param_error_exit;
>>> +    }
>>> +
>>> +    addr = rtas_ld(args, 0);
>>> +    option = rtas_ld(args, 3);
>>> +    switch (option) {
>>> +    case RTAS_EEH_ENABLE:
>>> +        if (!spapr_pci_find_dev(spapr, buid, addr)) {
>>> +            goto param_error_exit;
>>> +        }
>>> +        break;
>>> +    case RTAS_EEH_DISABLE:
>>> +    case RTAS_EEH_THAW_IO:
>>> +    case RTAS_EEH_THAW_DMA:
>>
>> So these don't use the addr hint?
>>
> 
> No, there're no address as argument of this RTAS call "ibm,set-eeh-option".
> The RTAS call has 4 arguments, all of them are 32-bits: BUID high part, BUID
> low part, PE address, option. The option could be one of: enable/disable EEH
> functionality, enable IO path, enable DMA path.

Well, I'm just wondering that ENABLE wants to make sure there's a device
and the others don't.


Alex