s390/airq: allow for airq structure that uses an input vector

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: Thomas Huth <thuth@redhat.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20220606203325.110625-7-mjrosato@linux.ibm.comSigned-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>

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);

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;
 

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);

drivers/s390/virtio/virtio_ccw.c

@@ -242,7 +242,7 @@ 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;