Linux Virtualization - May 2019 - [PATCH 10/10] virtio/s390: make airq summary indicators DMA

On 26/04/2019 20:32, Halil Pasic 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(-)
> 
> diff --git a/drivers/s390/virtio/virtio_ccw.c
b/drivers/s390/virtio/virtio_ccw.c
> index 613b18001a0c..6058b07fea08 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -140,11 +140,17 @@ static int virtio_ccw_use_airq = 1;
>   
>   struct airq_info {
>   	rwlock_t lock;
> -	u8 summary_indicator;
> +	u8 summary_indicator_idx;
>   	struct airq_struct airq;
>   	struct airq_iv *aiv;
>   };
>   static struct airq_info *airq_areas[MAX_AIRQ_AREAS];
> +static u8 *summary_indicators;
> +
> +static inline u8 *get_summary_indicator(struct airq_info *info)
> +{
> +	return summary_indicators + info->summary_indicator_idx;
> +}
>   
>   #define CCW_CMD_SET_VQ 0x13
>   #define CCW_CMD_VDEV_RESET 0x33
> @@ -225,7 +231,7 @@ static void virtio_airq_handler(struct airq_struct
*airq)
>   			break;
>   		vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv, ai));
>   	}
> -	info->summary_indicator = 0;
> +	*(get_summary_indicator(info)) = 0;
>   	smp_wmb();
>   	/* Walk through indicators field, summary indicator not active. */
>   	for (ai = 0;;) {
> @@ -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 */
> +static struct airq_info *new_airq_info(int index)
>   {
>   	struct airq_info *info;
>   	int rc;
> @@ -252,7 +259,8 @@ static struct airq_info *new_airq_info(void)
>   		return NULL;
>   	}
>   	info->airq.handler = virtio_airq_handler;
> -	info->airq.lsi_ptr = &info->summary_indicator;
> +	info->summary_indicator_idx = index;
> +	info->airq.lsi_ptr = get_summary_indicator(info);
>   	info->airq.lsi_mask = 0xff;
>   	info->airq.isc = VIRTIO_AIRQ_ISC;
>   	rc = register_adapter_interrupt(&info->airq);
> @@ -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 */
yes, my opinions too, was already racy, in my opinion, we need another 
patch in another series to fix this.

However, not sure about the comment.
>   		if (!airq_areas[i])
> -			airq_areas[i] = new_airq_info();
> +			airq_areas[i] = new_airq_info(i);
>   		info = airq_areas[i];
>   		if (!info)
>   			return 0;
> @@ -359,7 +368,7 @@ static void virtio_ccw_drop_indicator(struct
virtio_ccw_device *vcdev,
>   		if (!thinint_area)
>   			return;
>   		thinint_area->summary_indicator > -			(unsigned long)
&airq_info->summary_indicator;
> +			(unsigned long) get_summary_indicator(airq_info);
>   		thinint_area->isc = VIRTIO_AIRQ_ISC;
>   		ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
>   		ccw->count = sizeof(*thinint_area);
> @@ -624,7 +633,7 @@ static int virtio_ccw_register_adapter_ind(struct
virtio_ccw_device *vcdev,
>   	}
>   	info = vcdev->airq_info;
>   	thinint_area->summary_indicator > -		(unsigned long)
&info->summary_indicator;
> +		(unsigned long) get_summary_indicator(info);
>   	thinint_area->isc = VIRTIO_AIRQ_ISC;
>   	ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
>   	ccw->flags = CCW_FLAG_SLI;
> @@ -1500,6 +1509,7 @@ static int __init virtio_ccw_init(void)
>   {
>   	/* parse no_auto string before we do anything further */
>   	no_auto_parse();
> +	summary_indicators = cio_dma_zalloc(MAX_AIRQ_AREAS);
>   	return ccw_driver_register(&virtio_ccw_driver);
>   }
>   device_initcall(virtio_ccw_init);
> 


-- 
Pierre Morel
Linux/KVM/QEMU in B?blingen - Germany

On 08.05.19 17:11, Pierre Morel wrote:
> On 26/04/2019 20:32, Halil Pasic 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(-)
>>
>> diff --git a/drivers/s390/virtio/virtio_ccw.c 
>> b/drivers/s390/virtio/virtio_ccw.c
>> index 613b18001a0c..6058b07fea08 100644
>> --- a/drivers/s390/virtio/virtio_ccw.c
>> +++ b/drivers/s390/virtio/virtio_ccw.c
>> @@ -140,11 +140,17 @@ static int virtio_ccw_use_airq = 1;
>> ? struct airq_info {
>> ????? rwlock_t lock;
>> -??? u8 summary_indicator;
>> +??? u8 summary_indicator_idx;
>> ????? struct airq_struct airq;
>> ????? struct airq_iv *aiv;
>> ? };
>> ? static struct airq_info *airq_areas[MAX_AIRQ_AREAS];
>> +static u8 *summary_indicators;
>> +
>> +static inline u8 *get_summary_indicator(struct airq_info *info)
>> +{
>> +??? return summary_indicators + info->summary_indicator_idx;
>> +}
>> ? #define CCW_CMD_SET_VQ 0x13
>> ? #define CCW_CMD_VDEV_RESET 0x33
>> @@ -225,7 +231,7 @@ static void virtio_airq_handler(struct airq_struct 
>> *airq)
>> ????????????? break;
>> ????????? vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv,
ai));
>> ????? }
>> -??? info->summary_indicator = 0;
>> +??? *(get_summary_indicator(info)) = 0;
>> ????? smp_wmb();
>> ????? /* Walk through indicators field, summary indicator not active.
*/
>> ????? for (ai = 0;;) {
>> @@ -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 */
>> +static struct airq_info *new_airq_info(int index)
>> ? {
>> ????? struct airq_info *info;
>> ????? int rc;
>> @@ -252,7 +259,8 @@ static struct airq_info *new_airq_info(void)
>> ????????? return NULL;
>> ????? }
>> ????? info->airq.handler = virtio_airq_handler;
>> -??? info->airq.lsi_ptr = &info->summary_indicator;
>> +??? info->summary_indicator_idx = index;
>> +??? info->airq.lsi_ptr = get_summary_indicator(info);
>> ????? info->airq.lsi_mask = 0xff;
>> ????? info->airq.isc = VIRTIO_AIRQ_ISC;
>> ????? rc = register_adapter_interrupt(&info->airq);
>> @@ -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 */
> 
> yes, my opinions too, was already racy, in my opinion, we need another 
> patch in another series to fix this.
> 
> However, not sure about the comment.
I will drop this comment for v2 of this patch series.
We shall fix the race with a separate patch.

Michael
> 
>> ????????? if (!airq_areas[i])
>> -??????????? airq_areas[i] = new_airq_info();
>> +??????????? airq_areas[i] = new_airq_info(i);
>> ????????? info = airq_areas[i];
>> ????????? if (!info)
>> ????????????? return 0;
>> @@ -359,7 +368,7 @@ static void virtio_ccw_drop_indicator(struct 
>> virtio_ccw_device *vcdev,
>> ????????? if (!thinint_area)
>> ????????????? return;
>> ????????? thinint_area->summary_indicator >> -???????????
(unsigned long) &airq_info->summary_indicator;
>> +??????????? (unsigned long) get_summary_indicator(airq_info);
>> ????????? thinint_area->isc = VIRTIO_AIRQ_ISC;
>> ????????? ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
>> ????????? ccw->count = sizeof(*thinint_area);
>> @@ -624,7 +633,7 @@ static int virtio_ccw_register_adapter_ind(struct 
>> virtio_ccw_device *vcdev,
>> ????? }
>> ????? info = vcdev->airq_info;
>> ????? thinint_area->summary_indicator >> -??????? (unsigned
long) &info->summary_indicator;
>> +??????? (unsigned long) get_summary_indicator(info);
>> ????? thinint_area->isc = VIRTIO_AIRQ_ISC;
>> ????? ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
>> ????? ccw->flags = CCW_FLAG_SLI;
>> @@ -1500,6 +1509,7 @@ static int __init virtio_ccw_init(void)
>> ? {
>> ????? /* parse no_auto string before we do anything further */
>> ????? no_auto_parse();
>> +??? summary_indicators = cio_dma_zalloc(MAX_AIRQ_AREAS);
>> ????? return ccw_driver_register(&virtio_ccw_driver);
>> ? }
>> ? device_initcall(virtio_ccw_init);
>>
> 
> 
> 
-- 
Mit freundlichen Gr??en / Kind regards
Michael M?ller

IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Matthias Hartmann
Gesch?ftsf?hrung: Dirk Wittkopp
Sitz der Gesellschaft: B?blingen
Registergericht: Amtsgericht Stuttgart, HRB 243294

On Wed, 15 May 2019 15:33:02 +0200
Michael Mueller <mimu at linux.ibm.com> wrote:
> >> @@ -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 */  
> > 
> > yes, my opinions too, was already racy, in my opinion, we need another
> > patch in another series to fix this.
> > 
> > However, not sure about the comment.  
> 
> I will drop this comment for v2 of this patch series.
> We shall fix the race with a separate patch.
Unless there is somebody eager to address this real soon, I would prefer
keeping the comment as a reminder.

Thanks for shouldering the v2!

Regards,
Halil