Re: [PATCH for-5.2] s390x/pci: fix endianness issues

[Thomas Huth <thuth@redhat.com>]

On 18/11/2020 09.51, Cornelia Huck wrote:
> The zPCI group and function structures are big endian. However, we do
> not consistently store them as big endian locally, and are missing some
> conversions.
> 
> Let's just store the structures as host endian instead and convert to
> big endian when actually handling the instructions retrieving the data.
> 
> Also fix the layout of ClpReqQueryPciGrp: g is actually only 8 bit. This
> also fixes accesses on little endian hosts.
> 
> Fixes: 28dc86a07299 ("s390x/pci: use a PCI Group structure")
> Fixes: 9670ee752727 ("s390x/pci: use a PCI Function structure")
> Fixes: 1e7552ff5c34 ("s390x/pci: get zPCI function info from host")
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
> 
> Alternative approach to my patch from yesterday. The change is bigger,
> but the end result is arguably nicer.

Looks way better in my eyes, thanks!

[...]
> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> index 58cd041d17fb..6c36201229f3 100644
> --- a/hw/s390x/s390-pci-inst.c
> +++ b/hw/s390x/s390-pci-inst.c
> @@ -281,7 +281,12 @@ int clp_service_call(S390CPU *cpu, uint8_t r2, uintptr_t ra)
>              goto out;
>          }
>  
> -        memcpy(resquery, &pbdev->zpci_fn, sizeof(*resquery));
> +        stq_p(&resquery->sdma, pbdev->zpci_fn.sdma);
> +        stq_p(&resquery->edma, pbdev->zpci_fn.edma);
> +        stw_p(&resquery->pchid, pbdev->zpci_fn.pchid);
> +        resquery->pfgid = pbdev->zpci_fn.pfgid;
> +        stl_p(&resquery->fid, pbdev->zpci_fn.fid);
> +        stl_p(&resquery->uid, pbdev->zpci_fn.uid);

Looking at what had been removed in 9670ee7527279, I think you likely miss
this here:

        stw_p(&resquery->ug, pbdev->zpci_fn.ug)

?

>          for (i = 0; i < PCI_BAR_COUNT; i++) {
>              uint32_t data = pci_get_long(pbdev->pdev->config +
> @@ -313,6 +318,13 @@ int clp_service_call(S390CPU *cpu, uint8_t r2, uintptr_t ra)
>              goto out;
>          }
>          memcpy(resgrp, &group->zpci_group, sizeof(ClpRspQueryPciGrp));

I think you likely could remove the memcpy now, too?

> +        resgrp->fr = group->zpci_group.fr;
> +        stq_p(&resgrp->dasm, group->zpci_group.dasm);
> +        stq_p(&resgrp->msia, group->zpci_group.msia);
> +        stw_p(&resgrp->mui, group->zpci_group.mui);
> +        stw_p(&resgrp->i, group->zpci_group.i);
> +        stw_p(&resgrp->maxstbl, group->zpci_group.maxstbl);
> +        resgrp->version = group->zpci_group.version;
>          stw_p(&resgrp->hdr.rsp, CLP_RC_OK);
>          break;
>      }
[...]
> diff --git a/include/hw/s390x/s390-pci-clp.h b/include/hw/s390x/s390-pci-clp.h
> index ea2b1378cd5a..96b8e3f1331b 100644
> --- a/include/hw/s390x/s390-pci-clp.h
> +++ b/include/hw/s390x/s390-pci-clp.h
> @@ -144,10 +144,10 @@ typedef struct ClpReqQueryPciGrp {
>      ClpReqHdr hdr;
>      uint32_t fmt;
>      uint64_t reserved1;
> -#define CLP_REQ_QPCIG_MASK_PFGID 0xff
> -    uint32_t g;
> -    uint32_t reserved2;
> -    uint64_t reserved3;
> +    uint8_t reserved2[3];
> +    uint8_t g;
> +    uint32_t reserved3;
> +    uint64_t reserved4;
>  } QEMU_PACKED ClpReqQueryPciGrp;

This might even qualify as a separate patch, since it fixes a separate
problem on big endian hosts, too (g should have been masked with 0xff when
read as 32-bit value).

 Thomas