Re: [PATCH v3 06/30] s390/airq: allow for airq structure that uses an input vector

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Fri,  4 Feb 2022 16:15:12 -0500
Matthew Rosato <mjrosato@linux.ibm.com> wrote:

> When doing device passthrough where interrupts are being forwarded from
> host to guest, we wish to use a pinned section of guest memory as the
> vector (the same memory used by the guest as the vector). To accomplish
> this, add a new parameter for airq_iv_create which allows passing an
> existing vector to be used instead of allocating a new one. The caller
> is responsible for ensuring the vector is pinned in memory as well as for
> unpinning the memory when the vector is no longer needed.
> 
> A subsequent patch will use this new parameter for zPCI interpretation.
> 
> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/s390/include/asm/airq.h     |  4 +++-
>  arch/s390/pci/pci_irq.c          |  8 ++++----
>  drivers/s390/cio/airq.c          | 10 +++++++---
>  drivers/s390/virtio/virtio_ccw.c |  2 +-
>  4 files changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/s390/include/asm/airq.h b/arch/s390/include/asm/airq.h
> index 7918a7d09028..e82e5626e139 100644
> --- a/arch/s390/include/asm/airq.h
> +++ b/arch/s390/include/asm/airq.h
> @@ -47,8 +47,10 @@ struct airq_iv {
>  #define AIRQ_IV_PTR		4	/* Allocate the ptr array */
>  #define AIRQ_IV_DATA		8	/* Allocate the data array */
>  #define AIRQ_IV_CACHELINE	16	/* Cacheline alignment for the vector */
> +#define AIRQ_IV_GUESTVEC	32	/* Vector is a pinned guest page */
>  
> -struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags);
> +struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags,
> +			       unsigned long *vec);
>  void airq_iv_release(struct airq_iv *iv);
>  unsigned long airq_iv_alloc(struct airq_iv *iv, unsigned long num);
>  void airq_iv_free(struct airq_iv *iv, unsigned long bit, unsigned long num);
> diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
> index cc4c8d7c8f5c..0d0a02a9fbbf 100644
> --- a/arch/s390/pci/pci_irq.c
> +++ b/arch/s390/pci/pci_irq.c
> @@ -296,7 +296,7 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
>  		zdev->aisb = bit;
>  
>  		/* Create adapter interrupt vector */
> -		zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA | AIRQ_IV_BITLOCK);
> +		zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA | AIRQ_IV_BITLOCK, NULL);
>  		if (!zdev->aibv)
>  			return -ENOMEM;
>  
> @@ -419,7 +419,7 @@ static int __init zpci_directed_irq_init(void)
>  	union zpci_sic_iib iib = {{0}};
>  	unsigned int cpu;
>  
> -	zpci_sbv = airq_iv_create(num_possible_cpus(), 0);
> +	zpci_sbv = airq_iv_create(num_possible_cpus(), 0, NULL);
>  	if (!zpci_sbv)
>  		return -ENOMEM;
>  
> @@ -441,7 +441,7 @@ static int __init zpci_directed_irq_init(void)
>  		zpci_ibv[cpu] = airq_iv_create(cache_line_size() * BITS_PER_BYTE,
>  					       AIRQ_IV_DATA |
>  					       AIRQ_IV_CACHELINE |
> -					       (!cpu ? AIRQ_IV_ALLOC : 0));
> +					       (!cpu ? AIRQ_IV_ALLOC : 0), NULL);
>  		if (!zpci_ibv[cpu])
>  			return -ENOMEM;
>  	}
> @@ -458,7 +458,7 @@ static int __init zpci_floating_irq_init(void)
>  	if (!zpci_ibv)
>  		return -ENOMEM;
>  
> -	zpci_sbv = airq_iv_create(ZPCI_NR_DEVICES, AIRQ_IV_ALLOC);
> +	zpci_sbv = airq_iv_create(ZPCI_NR_DEVICES, AIRQ_IV_ALLOC, NULL);
>  	if (!zpci_sbv)
>  		goto out_free;
>  
> diff --git a/drivers/s390/cio/airq.c b/drivers/s390/cio/airq.c
> index 2f2226786319..375a58b1c838 100644
> --- a/drivers/s390/cio/airq.c
> +++ b/drivers/s390/cio/airq.c
> @@ -122,10 +122,12 @@ static inline unsigned long iv_size(unsigned long bits)
>   * airq_iv_create - create an interrupt vector
>   * @bits: number of bits in the interrupt vector
>   * @flags: allocation flags
> + * @vec: pointer to pinned guest memory if AIRQ_IV_GUESTVEC
>   *
>   * Returns a pointer to an interrupt vector structure
>   */
> -struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags)
> +struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags,
> +			       unsigned long *vec)
>  {
>  	struct airq_iv *iv;
>  	unsigned long size;
> @@ -146,6 +148,8 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags)
>  					     &iv->vector_dma);
>  		if (!iv->vector)
>  			goto out_free;
> +	} else if (flags & AIRQ_IV_GUESTVEC) {
> +		iv->vector = vec;
>  	} else {
>  		iv->vector = cio_dma_zalloc(size);
>  		if (!iv->vector)
> @@ -185,7 +189,7 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags)
>  	kfree(iv->avail);
>  	if (iv->flags & AIRQ_IV_CACHELINE && iv->vector)
>  		dma_pool_free(airq_iv_cache, iv->vector, iv->vector_dma);
> -	else
> +	else if (!(iv->flags & AIRQ_IV_GUESTVEC))
>  		cio_dma_free(iv->vector, size);
>  	kfree(iv);
>  out:
> @@ -204,7 +208,7 @@ void airq_iv_release(struct airq_iv *iv)
>  	kfree(iv->bitlock);
>  	if (iv->flags & AIRQ_IV_CACHELINE)
>  		dma_pool_free(airq_iv_cache, iv->vector, iv->vector_dma);
> -	else
> +	else if (!(iv->flags & AIRQ_IV_GUESTVEC))
>  		cio_dma_free(iv->vector, iv_size(iv->bits));
>  	kfree(iv->avail);
>  	kfree(iv);
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index 52c376d15978..410498d693f8 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -241,7 +241,7 @@ static struct airq_info *new_airq_info(int index)
>  		return NULL;
>  	rwlock_init(&info->lock);
>  	info->aiv = airq_iv_create(VIRTIO_IV_BITS, AIRQ_IV_ALLOC | AIRQ_IV_PTR
> -				   | AIRQ_IV_CACHELINE);
> +				   | AIRQ_IV_CACHELINE, NULL);
>  	if (!info->aiv) {
>  		kfree(info);
>  		return NULL;