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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.10.14 at 11:54, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 30 September 2014 10:49
>> To: Andrew Cooper; Paul Durrant
>> Cc: xen-devel@xxxxxxxxxxxxx; Keir (Xen.org)
>> Subject: RE: [Xen-devel] [PATCH v3 for 4.5] ioreq-server: handle the lack of 
>> a
>> default emulator properly
>> 
>> >>> On 30.09.14 at 11:43, <Paul.Durrant@xxxxxxxxxx> wrote:
>> >>  -----Original Message-----
>> >> From: Andrew Cooper
>> >> Sent: 30 September 2014 10:29
>> >> To: Paul Durrant; xen-devel@xxxxxxxxxxxxx 
>> >> Cc: Keir (Xen.org); Jan Beulich
>> >> Subject: Re: [Xen-devel] [PATCH v3 for 4.5] ioreq-server: handle the lack
>> of a
>> >> default emulator properly
>> >>
>> >> 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 )
>> >>
>> >
>> > <Sigh> Yes, missed that one.
>> 
>> And I can fix that while committing...
>> 
> 
> BTW, can I take that as an ack?

Sure, but is that still relevant considering that the patch got committed
already?

Jan


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