From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH 08/10] virtio/s390: add indirection to indicators access References: <20190426183245.37939-1-pasic@linux.ibm.com> <20190426183245.37939-9-pasic@linux.ibm.com> <716d47ca-016f-e8f4-6d78-7746a7d9f6ba@linux.ibm.com> <20190509202600.4fd6aebe.pasic@linux.ibm.com> From: Pierre Morel Date: Fri, 10 May 2019 09:43:08 +0200 MIME-Version: 1.0 In-Reply-To: <20190509202600.4fd6aebe.pasic@linux.ibm.com> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 8bit Message-Id: Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Halil Pasic Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, Cornelia Huck , Martin Schwidefsky , Sebastian Ott , virtualization@lists.linux-foundation.org, "Michael S. Tsirkin" , Christoph Hellwig , Thomas Huth , Christian Borntraeger , Viktor Mihajlovski , Vasily Gorbik , Janosch Frank , Claudio Imbrenda , Farhan Ali , Eric Farman List-ID: On 09/05/2019 20:26, Halil Pasic wrote: > On Thu, 9 May 2019 14:01:01 +0200 > Pierre Morel wrote: > >> On 08/05/2019 16:31, Pierre Morel wrote: >>> On 26/04/2019 20:32, Halil Pasic wrote: >>>> This will come in handy soon when we pull out the indicators from >>>> virtio_ccw_device to a memory area that is shared with the hypervisor >>>> (in particular for protected virtualization guests). >>>> >>>> Signed-off-by: Halil Pasic >>>> --- >>>>   drivers/s390/virtio/virtio_ccw.c | 40 >>>> +++++++++++++++++++++++++--------------- >>>>   1 file changed, 25 insertions(+), 15 deletions(-) >>>> >>>> diff --git a/drivers/s390/virtio/virtio_ccw.c >>>> b/drivers/s390/virtio/virtio_ccw.c >>>> index bb7a92316fc8..1f3e7d56924f 100644 >>>> --- a/drivers/s390/virtio/virtio_ccw.c >>>> +++ b/drivers/s390/virtio/virtio_ccw.c >>>> @@ -68,6 +68,16 @@ struct virtio_ccw_device { >>>>       void *airq_info; >>>>   }; >>>> +static inline unsigned long *indicators(struct virtio_ccw_device *vcdev) >>>> +{ >>>> +    return &vcdev->indicators; >>>> +} >>>> + >>>> +static inline unsigned long *indicators2(struct virtio_ccw_device >>>> *vcdev) >>>> +{ >>>> +    return &vcdev->indicators2; >>>> +} >>>> + >>>>   struct vq_info_block_legacy { >>>>       __u64 queue; >>>>       __u32 align; >>>> @@ -337,17 +347,17 @@ static void virtio_ccw_drop_indicator(struct >>>> virtio_ccw_device *vcdev, >>>>           ccw->cda = (__u32)(unsigned long) thinint_area; >>>>       } else { >>>>           /* payload is the address of the indicators */ >>>> -        indicatorp = kmalloc(sizeof(&vcdev->indicators), >>>> +        indicatorp = kmalloc(sizeof(indicators(vcdev)), >>>>                        GFP_DMA | GFP_KERNEL); >>>>           if (!indicatorp) >>>>               return; >>>>           *indicatorp = 0; >>>>           ccw->cmd_code = CCW_CMD_SET_IND; >>>> -        ccw->count = sizeof(&vcdev->indicators); >>>> +        ccw->count = sizeof(indicators(vcdev)); >>> >>> This looks strange to me. Was already weird before. >>> Lucky we are indicators are long... >>> may be just sizeof(long) >> > > I'm not sure I understand where are you coming from... > > With CCW_CMD_SET_IND we tell the hypervisor the guest physical address > at which the so called classic indicators. There is a comment that > makes this obvious. The argument of the sizeof was and remained a > pointer type. AFAIU this is what bothers you. >> >> AFAIK the size of the indicators (AIV/AIS) is not restricted by the >> architecture. > > The size of vcdev->indicators is restricted or defined by the virtio > specification. Please have a look at '4.3.2.6.1 Setting Up Classic Queue > Indicators' here: > https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-1630002 > > Since with Linux on s390 only 64 bit is supported, both the sizes are in > line with the specification. Using u64 would semantically match the spec > better, modulo pre virtio 1.0 which ain't specified. I did not want to > do changes that are not necessary for what I'm trying to accomplish. If > we want we can change these to u64 with a patch on top. I mean you are changing these line already, so why not doing it right while at it? Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany