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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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...

Jan


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