Re: [Qemu-devel] [PATCH v18 1/2] sPAPR: Implement EEH RTAS calls

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Gavin Shan (2015-02-15 23:32:09)
> On Mon, Feb 16, 2015 at 12:52:48PM +1100, David Gibson wrote:
> >On Mon, Feb 16, 2015 at 10:16:01AM +1100, 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
> >> callbacks sPAPRPHBClass::{eeh_set_option, eeh_get_state, eeh_reset,
> >> eeh_configure}, which are going to be used as follows:
> >> 
> >>   * 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 the corresponding sPAPRPHBClass callback is
> >>     defined, it is called.
> >>   * Those callbacks are only implemented for VFIO now. They do ioctl()
> >>     to the IOMMU container fd to complete the calls. 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          | 281 ++++++++++++++++++++++++++++++++++++++++++++
> >>  include/hw/pci-host/spapr.h |   4 +
> >>  include/hw/ppc/spapr.h      |  43 ++++++-
> >>  3 files changed, 326 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> >> index cebdeb3..29b071d 100644
> >> --- a/hw/ppc/spapr_pci.c
> >> +++ b/hw/ppc/spapr_pci.c
> >> @@ -406,6 +406,268 @@ static void rtas_ibm_query_interrupt_source_number(PowerPCCPU *cpu,
> >>      rtas_st(rets, 2, 1);/* 0 == level; 1 == edge */
> >>  }
> >>  
> >> +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)
> >> +{
> >> +    sPAPRPHBState *sphb;
> >> +    sPAPRPHBClass *spc;
> >> +    uint32_t addr, option;
> >> +    uint64_t buid;
> >> +    int ret;
> >> +
> >> +    if ((nargs != 4) || (nret != 1)) {
> >> +        goto param_error_exit;
> >> +    }
> >> +
> >> +    buid = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 2);
> >> +    addr = rtas_ld(args, 0);
> >> +    option = rtas_ld(args, 3);
> >> +
> >> +    sphb = find_phb(spapr, buid);
> >> +    if (!sphb) {
> >> +        goto param_error_exit;
> >> +    }
> >> +
> >> +    spc = SPAPR_PCI_HOST_BRIDGE_GET_CLASS(sphb);
> >> +    if (!spc->eeh_set_option) {
> >> +        goto param_error_exit;
> >> +    }
> >> +
> >> +    /*
> >> +     * The EEH functionality is enabled on basis of PCI device,
> >> +     * instead of PE. We need check the validity of the PCI
> >> +     * device address.
> >> +     */
> >> +    if (option == RTAS_EEH_ENABLE &&
> >> +        !find_dev(spapr, buid, addr)) {
> >> +        goto param_error_exit;
> >> +    }
> >
> >You're still breaking your layering by doing checks dependent on the
> >specific option both here and in the callback.
> >
> >What I meant by my comments on the previous version was that this
> >find_dev() test should also move into the eeh_set_option callback.
> >Obviously that means adding addr into the parameters - but surely if
> >the addr has any meaning whatsoever, it must be at least potentially
> >needed by the callback anyway.
> >
> 
> Ok. Either simply dropping the check here, or moving find_dev() to
> sPAPRPHBClass::eeh_set_option() as you suggested. However, there're more
> things needed for sPAPRPHBClass::eeh_set_option() to do the check as follows.
> David, could you help to confirm which way you prefer?
> 
> - Rename find_dev() to spapr_find_pci_dev() and make it public. It will be
>   called in spapr_pci_vfio.c
> - Add one field sPAPRPHBState::spapr to reference the associated sPAPREnvironment,
>   which is required by spapr_find_pci_dev(). Otherwise, we have to pass sPAPREnvironment
>   to sPAPRPHBClass::eeh_set_option().

AFAICT spapr_pci.c:find_dev() only needs sPAPREnvironment to look up the phb
given a buid, but in your case you already have the phb and pass it on to
eeh_set_option(), so within eeh_set_option() you can call pci_find_device()
just like spapr_pci.c:find_dev() does to do the validation.

The validation seems to assume the addr value is a config_addr for the device
though, isn't it possible we might recieve a pe_addr of the form returned
by rtas_ibm_get_config_addr_info2? That value would happen to correspond to
bus:n,device:0,func:0,reg:1, and find_dev in that case would just mask off
the reg value and verify there's a device in PCI slot 0, instead of whatever
actually needs to be validated in that situation (which isn't clear to me).

> 
> Thanks,
> Gavin
> 
> >Apart from that,
> >
> >Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> >
> >-- 
> >David Gibson                   | I'll have my music baroque, and my code
> >david AT gibson.dropbear.id.au | minimalist, thank you.  NOT _the_ _other_
> >                               | _way_ _around_!
> >http://www.ozlabs.org/~dgibson