Re: [Xen-devel] [PATCH] ioreq-server: handle IOREQ_TYPE_PCI_CONFIG in assist function

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx]
> Sent: 27 January 2015 19:06
> To: xen-devel@xxxxxxxxxxxxx
> Cc: Wei Liu; Jan Beulich; Paul Durrant; Andrew Cooper
> Subject: [PATCH] ioreq-server: handle IOREQ_TYPE_PCI_CONFIG in assist
> function
> 
> QEMU stubdom will read PCI config space when enumerating PCI devices.
> Xen should return ~0 when there is no suitable ioreq server to dispatch
> the request.
> 
> Without this patch, QEMU stubdom will fail to start because hvmloader
> fails following assertion:
> 
> 118         ASSERT((devfn != PCI_ISA_DEVFN) ||
> 119                ((vendor_id == 0x8086) && (device_id == 0x7000)));
> 
> because vendor_id and device_id are 0.
> 
> This fixes a regression for QEMU stubdom. It should be backported to 4.5
> as well.
> 
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

No, you should not need this. If you look at the code closely you'll see that 
hvm_complete_assist_req() is only called if hvm_select_ioreq_server() returns 
NULL, and the switch from IOREQ_TYPE_PIO to IOREQ_TYPE_PCI_CONFIG is only made 
if a non-default ioreq server matches the current cf8. Hence we could actually 
ASSERT(p->type !- IOREQ_TYPE_PCI_CONFIG) at the top of 
hvm_complete_assist_req().

  Paul

> ---
>  xen/arch/x86/hvm/hvm.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index c7984d1..c826ac5 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2577,6 +2577,7 @@ static bool_t hvm_complete_assist_req(ioreq_t *p)
>      {
>      case IOREQ_TYPE_COPY:
>      case IOREQ_TYPE_PIO:
> +    case IOREQ_TYPE_PCI_CONFIG:
>          if ( p->dir == IOREQ_READ )
>          {
>              if ( !p->data_is_ptr )
> --
> 1.9.1


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