Re: [Xen-devel] [PATCH v3 for 4.5] ioreq-server: handle the lack of a default emulator properly

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/09/14 10:29, Andrew Cooper wrote:
> On 30/09/14 10:18, Paul Durrant wrote:
>> I started porting QEMU over to use the new ioreq server API and hit a
>> problem with PCI bus enumeration. Because, with my patches, QEMU only
>> registers to handle config space accesses for the PCI device it implements
>> all other attempts by the guest to access 0xcfc go nowhere and this was
>> causing the vcpu to wedge up because nothing was completing the I/O.
>>
>> This patch introduces an I/O completion handler into the hypervisor for the
>> case where no ioreq server matches a particular request. Read requests are
>> completed with 0xf's in the data buffer, writes and all other I/O req types
>> are ignored.
>>
>> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
>> Cc: Keir Fraser <keir@xxxxxxx>
>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> One bug, couple of nits.
>
> It is probably worth having a sentence in the commit message concerning
> the removal of list_is_singular().
>
>> ---
>> v3: - Fix for backwards string instruction emulation
>>
>> v2: - First non-RFC submission
>>     - Removed warning on unemulated MMIO accesses
>>
>>  xen/arch/x86/hvm/hvm.c |   35 ++++++++++++++++++++++++++++++++---
>>  1 file changed, 32 insertions(+), 3 deletions(-)
>>
>> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
>> index 5c7e0a4..e6611ed 100644
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -2386,8 +2386,7 @@ static struct hvm_ioreq_server 
>> *hvm_select_ioreq_server(struct domain *d,
>>      if ( list_empty(&d->arch.hvm_domain.ioreq_server.list) )
>>          return NULL;
>>  
>> -    if ( list_is_singular(&d->arch.hvm_domain.ioreq_server.list) ||
>> -         (p->type != IOREQ_TYPE_COPY && p->type != IOREQ_TYPE_PIO) )
>> +    if ( p->type != IOREQ_TYPE_COPY && p->type != IOREQ_TYPE_PIO )
>>          return d->arch.hvm_domain.default_ioreq_server;
>>  
>>      cf8 = d->arch.hvm_domain.pci_cf8;
>> @@ -2618,12 +2617,42 @@ bool_t hvm_send_assist_req_to_ioreq_server(struct 
>> hvm_ioreq_server *s,
>>      return 0;
>>  }
>>  
>> +static bool_t hvm_complete_assist_req(ioreq_t *p)
>> +{
>> +    switch (p->type)
> Style: ( p-> type )

Hmm - I am not sure where the space following -> appeared from, but I
meant "( p->type )".  Apologies.

~Andrew

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