Re: [PATCH v5 4/8] s390/airq: use DMA memory for adapter interrupts

[Michael Mueller <mimu@linux.ibm.com>]

On 12.06.19 13:12, Halil Pasic wrote:
> Protected virtualization guests have to use shared pages for airq
> notifier bit vectors, because hypervisor needs to write these bits.

because the hypervisor

> 
> Let us make sure we allocate DMA memory for the notifier bit vectors by
> replacing the kmem_cache with a dma_cache and kalloc() with
> cio_dma_zalloc().
> 
> Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> Reviewed-by: Sebastian Ott <sebott@linux.ibm.com>
> ---
>   arch/s390/include/asm/airq.h |  2 ++
>   drivers/s390/cio/airq.c      | 37 ++++++++++++++++++++++--------------
>   drivers/s390/cio/cio.h       |  2 ++
>   drivers/s390/cio/css.c       |  1 +
>   4 files changed, 28 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/s390/include/asm/airq.h b/arch/s390/include/asm/airq.h
> index c10d2ee2dfda..01936fdfaddb 100644
> --- a/arch/s390/include/asm/airq.h
> +++ b/arch/s390/include/asm/airq.h
> @@ -11,6 +11,7 @@
>   #define _ASM_S390_AIRQ_H
>   
>   #include <linux/bit_spinlock.h>
> +#include <linux/dma-mapping.h>
>   
>   struct airq_struct {
>   	struct hlist_node list;		/* Handler queueing. */
> @@ -29,6 +30,7 @@ void unregister_adapter_interrupt(struct airq_struct *airq);
>   /* Adapter interrupt bit vector */
>   struct airq_iv {
>   	unsigned long *vector;	/* Adapter interrupt bit vector */
> +	dma_addr_t vector_dma; /* Adapter interrupt bit vector dma */
>   	unsigned long *avail;	/* Allocation bit mask for the bit vector */
>   	unsigned long *bitlock;	/* Lock bit mask for the bit vector */
>   	unsigned long *ptr;	/* Pointer associated with each bit */
> diff --git a/drivers/s390/cio/airq.c b/drivers/s390/cio/airq.c
> index 4534afc63591..427b2e24a8ce 100644
> --- a/drivers/s390/cio/airq.c
> +++ b/drivers/s390/cio/airq.c
> @@ -16,9 +16,11 @@
>   #include <linux/mutex.h>
>   #include <linux/rculist.h>
>   #include <linux/slab.h>
> +#include <linux/dmapool.h>
>   
>   #include <asm/airq.h>
>   #include <asm/isc.h>
> +#include <asm/cio.h>
>   
>   #include "cio.h"
>   #include "cio_debug.h"
> @@ -27,7 +29,7 @@
>   static DEFINE_SPINLOCK(airq_lists_lock);
>   static struct hlist_head airq_lists[MAX_ISC+1];
>   
> -static struct kmem_cache *airq_iv_cache;
> +static struct dma_pool *airq_iv_cache;
>   
>   /**
>    * register_adapter_interrupt() - register adapter interrupt handler
> @@ -115,6 +117,11 @@ void __init init_airq_interrupts(void)
>   	setup_irq(THIN_INTERRUPT, &airq_interrupt);
>   }
>   
> +static inline unsigned long iv_size(unsigned long bits)
> +{
> +	return BITS_TO_LONGS(bits) * sizeof(unsigned long);
> +}
> +
>   /**
>    * airq_iv_create - create an interrupt vector
>    * @bits: number of bits in the interrupt vector
> @@ -132,17 +139,19 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags)
>   		goto out;
>   	iv->bits = bits;
>   	iv->flags = flags;
> -	size = BITS_TO_LONGS(bits) * sizeof(unsigned long);
> +	size = iv_size(bits);
>   
>   	if (flags & AIRQ_IV_CACHELINE) {
> -		if ((cache_line_size() * BITS_PER_BYTE) < bits)
> +		if ((cache_line_size() * BITS_PER_BYTE) < bits
> +				|| !airq_iv_cache)
>   			goto out_free;
>   
> -		iv->vector = kmem_cache_zalloc(airq_iv_cache, GFP_KERNEL);
> +		iv->vector = dma_pool_zalloc(airq_iv_cache, GFP_KERNEL,
> +					     &iv->vector_dma);
>   		if (!iv->vector)
>   			goto out_free;
>   	} else {
> -		iv->vector = kzalloc(size, GFP_KERNEL);
> +		iv->vector = cio_dma_zalloc(size);
>   		if (!iv->vector)
>   			goto out_free;
>   	}
> @@ -178,10 +187,10 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags)
>   	kfree(iv->ptr);
>   	kfree(iv->bitlock);
>   	kfree(iv->avail);
> -	if (iv->flags & AIRQ_IV_CACHELINE)
> -		kmem_cache_free(airq_iv_cache, iv->vector);
> +	if (iv->flags & AIRQ_IV_CACHELINE && iv->vector)
> +		dma_pool_free(airq_iv_cache, iv->vector, iv->vector_dma);
>   	else
> -		kfree(iv->vector);
> +		cio_dma_free(iv->vector, size);
>   	kfree(iv);
>   out:
>   	return NULL;
> @@ -198,9 +207,9 @@ void airq_iv_release(struct airq_iv *iv)
>   	kfree(iv->ptr);
>   	kfree(iv->bitlock);
>   	if (iv->flags & AIRQ_IV_CACHELINE)
> -		kmem_cache_free(airq_iv_cache, iv->vector);
> +		dma_pool_free(airq_iv_cache, iv->vector, iv->vector_dma);
>   	else
> -		kfree(iv->vector);
> +		cio_dma_free(iv->vector, iv_size(iv->bits));
>   	kfree(iv->avail);
>   	kfree(iv);
>   }
> @@ -295,12 +304,12 @@ unsigned long airq_iv_scan(struct airq_iv *iv, unsigned long start,
>   }
>   EXPORT_SYMBOL(airq_iv_scan);
>   
> -static int __init airq_init(void)
> +int __init airq_init(void)
>   {
> -	airq_iv_cache = kmem_cache_create("airq_iv_cache", cache_line_size(),
> -					  cache_line_size(), 0, NULL);
> +	airq_iv_cache = dma_pool_create("airq_iv_cache", cio_get_dma_css_dev(),
> +					cache_line_size(),
> +					cache_line_size(), PAGE_SIZE);
>   	if (!airq_iv_cache)
>   		return -ENOMEM;
>   	return 0;
>   }
> -subsys_initcall(airq_init);
> diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h
> index 06a91743335a..4d6c7d16416e 100644
> --- a/drivers/s390/cio/cio.h
> +++ b/drivers/s390/cio/cio.h
> @@ -135,6 +135,8 @@ extern int cio_commit_config(struct subchannel *sch);
>   int cio_tm_start_key(struct subchannel *sch, struct tcw *tcw, u8 lpm, u8 key);
>   int cio_tm_intrg(struct subchannel *sch);
>   
> +extern int __init airq_init(void);
> +
>   /* Use with care. */
>   #ifdef CONFIG_CCW_CONSOLE
>   extern struct subchannel *cio_probe_console(void);
> diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
> index e0f19f1e82a0..1b867c941b86 100644
> --- a/drivers/s390/cio/css.c
> +++ b/drivers/s390/cio/css.c
> @@ -1184,6 +1184,7 @@ static int __init css_bus_init(void)
>   	ret = cio_dma_pool_init();
>   	if (ret)
>   		goto out_unregister_pmn;
> +	airq_init();
>   	css_init_done = 1;
>   
>   	/* Enable default isc for I/O subchannels. */
> 

Reviewed-by: Michael Mueller <mimu@linux.ibm.com>

Michael