Cornelia Huck
2019-May-13 12:20 UTC
[PATCH 10/10] virtio/s390: make airq summary indicators DMA
On Fri, 26 Apr 2019 20:32:45 +0200 Halil Pasic <pasic at linux.ibm.com> wrote:> Hypervisor needs to interact with the summary indicators, so these > need to be DMA memory as well (at least for protected virtualization > guests). > > Signed-off-by: Halil Pasic <pasic at linux.ibm.com> > --- > drivers/s390/virtio/virtio_ccw.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-)(...)> @@ -237,7 +243,8 @@ static void virtio_airq_handler(struct airq_struct *airq) > read_unlock(&info->lock); > } > > -static struct airq_info *new_airq_info(void) > +/* call with airq_areas_lock held */Hm, where is airq_areas_lock defined? If it was introduced in one of the previous patches, I have missed it.> +static struct airq_info *new_airq_info(int index) > { > struct airq_info *info; > int rc;
Michael Mueller
2019-May-15 13:43 UTC
[PATCH 10/10] virtio/s390: make airq summary indicators DMA
On 13.05.19 14:20, Cornelia Huck wrote:> On Fri, 26 Apr 2019 20:32:45 +0200 > Halil Pasic <pasic at linux.ibm.com> wrote: > >> Hypervisor needs to interact with the summary indicators, so these >> need to be DMA memory as well (at least for protected virtualization >> guests). >> >> Signed-off-by: Halil Pasic <pasic at linux.ibm.com> >> --- >> drivers/s390/virtio/virtio_ccw.c | 24 +++++++++++++++++------- >> 1 file changed, 17 insertions(+), 7 deletions(-) > > (...) > >> @@ -237,7 +243,8 @@ static void virtio_airq_handler(struct airq_struct *airq) >> read_unlock(&info->lock); >> } >> >> -static struct airq_info *new_airq_info(void) >> +/* call with drivers/s390/virtio/virtio_ccw.cheld */ > > Hm, where is airq_areas_lock defined? If it was introduced in one of > the previous patches, I have missed it.There is no airq_areas_lock defined currently. My assumption is that this will be used in context with the likely race condition this part of the patch is talking about. @@ -273,8 +281,9 @@ static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs, unsigned long bit, flags; for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) { + /* TODO: this seems to be racy */ if (!airq_areas[i]) - airq_areas[i] = new_airq_info(); + airq_areas[i] = new_airq_info(i); As this shall be handled by a separate patch I will drop the comment in regard to airq_areas_lock from this patch as well for v2. Michael> >> +static struct airq_info *new_airq_info(int index) >> { >> struct airq_info *info; >> int rc; >
Cornelia Huck
2019-May-15 13:50 UTC
[PATCH 10/10] virtio/s390: make airq summary indicators DMA
On Wed, 15 May 2019 15:43:23 +0200 Michael Mueller <mimu at linux.ibm.com> wrote:> On 13.05.19 14:20, Cornelia Huck wrote: > > On Fri, 26 Apr 2019 20:32:45 +0200 > > Halil Pasic <pasic at linux.ibm.com> wrote: > > > >> Hypervisor needs to interact with the summary indicators, so these > >> need to be DMA memory as well (at least for protected virtualization > >> guests). > >> > >> Signed-off-by: Halil Pasic <pasic at linux.ibm.com> > >> --- > >> drivers/s390/virtio/virtio_ccw.c | 24 +++++++++++++++++------- > >> 1 file changed, 17 insertions(+), 7 deletions(-) > > > > (...) > > > >> @@ -237,7 +243,8 @@ static void virtio_airq_handler(struct airq_struct *airq) > >> read_unlock(&info->lock); > >> } > >> > >> -static struct airq_info *new_airq_info(void) > >> +/* call with drivers/s390/virtio/virtio_ccw.cheld */ > > > > Hm, where is airq_areas_lock defined? If it was introduced in one of > > the previous patches, I have missed it. > > There is no airq_areas_lock defined currently. My assumption is that > this will be used in context with the likely race condition this > part of the patch is talking about. > > @@ -273,8 +281,9 @@ static unsigned long get_airq_indicator(struct > virtqueue *vqs[], int nvqs, > unsigned long bit, flags; > > for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) { > + /* TODO: this seems to be racy */ > if (!airq_areas[i]) > - airq_areas[i] = new_airq_info(); > + airq_areas[i] = new_airq_info(i); > > > As this shall be handled by a separate patch I will drop the comment > in regard to airq_areas_lock from this patch as well for v2.Ok, that makes sense.
Halil Pasic
2019-May-15 17:18 UTC
[PATCH 10/10] virtio/s390: make airq summary indicators DMA
On Wed, 15 May 2019 15:43:23 +0200 Michael Mueller <mimu at linux.ibm.com> wrote:> > Hm, where is airq_areas_lock defined? If it was introduced in one of > > the previous patches, I have missed it. > > There is no airq_areas_lock defined currently. My assumption is that > this will be used in context with the likely race condition this > part of the patch is talking about.Right! I first started resolving the race, but then decided to discuss the issue first, because if I were to just have hallucinated that race, it would be a lots of wasted effort. Unfortunately I forgot to get rid of this comment. Regards, Halil
Reasonably Related Threads
- [PATCH 10/10] virtio/s390: make airq summary indicators DMA
- [PATCH 10/10] virtio/s390: make airq summary indicators DMA
- [PATCH 10/10] virtio/s390: make airq summary indicators DMA
- [PATCH v3 8/8] virtio/s390: make airq summary indicators DMA
- [PATCH v2 8/8] virtio/s390: make airq summary indicators DMA