Re: [Qemu-devel] [PATCH 2/3] s390x/pci: fixup global refresh

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 30 Jan 2018 10:47:14 +0100
Yi Min Zhao <zyimin@linux.vnet.ibm.com> wrote:

> The VFIO common code doesn't provide the possibility to modify a
> previous mapping entry in another way than unmapping and mapping again
> with new properties.

I'm wondering why other architectures don't need that. Is this
refreshing an unique ability on s390 (due to that instruction)?

> 
> To avoid -EEXIST DMA mapping error, this we introduce a GHashTable to

s/this//

> store S390IOTLBEntry instances in order to cache the mapped entries.
> When intercepting rpcit instruction, ignore the identical mapped
> entries to avoid doing map operations multiple times and do unmap and
> re-map operations for the case of updating the valid entries. To
> achieve that goal, we also export the DMA walking function and
> optimize the code handling errors in rpcit handler.

How often does such a thing happen in practice?

> 
> Acked-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
> Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
> ---
>  hw/s390x/s390-pci-bus.c  | 28 +++++++++-----
>  hw/s390x/s390-pci-bus.h  |  3 ++
>  hw/s390x/s390-pci-inst.c | 95 ++++++++++++++++++++++++++++++++++--------------
>  3 files changed, 90 insertions(+), 36 deletions(-)

Can't really review the rest due to -ENODOC, sorry.