[PATCH v4 01/10] PCI/MSI: Support allocating virtual MSI interrupts

Logan Gunthorpe
2019-04-22T21:06:44Z

For NTB devices, we want to be able to trigger MSI interrupts
through a memory window. In these cases we may want to use
more interrupts than the NTB PCI device has available in its MSI-X
table.

We allow for this by creating a new 'virtual' interrupt. These
interrupts are allocated as usual but are not programmed into the
MSI-X table (as there may not be space for them).

The MSI address and data will then handled through an NTB MSI library
introduced later in this series.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/msi.c | 54 +++++++++++++++++++++++++++++++++++++--------
include/linux/msi.h | 8 +++++++
include/linux/pci.h | 9 ++++++++
3 files changed, 62 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 73986825d221..668bc16ef4d1 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -192,6 +192,9 @@ static void msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)

static void __iomem *pci_msix_desc_addr(struct msi_desc *desc)
{
+ if (desc->msi_attrib.is_virtual)
+ return NULL;
+
return desc->mask_base +
desc->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;
}
@@ -206,14 +209,19 @@ static void __iomem *pci_msix_desc_addr(struct msi_desc *desc)
u32 __pci_msix_desc_mask_irq(struct msi_desc *desc, u32 flag)
{
u32 mask_bits = desc->masked;
+ void __iomem *desc_addr;

if (pci_msi_ignore_mask)
return 0;
+ desc_addr = pci_msix_desc_addr(desc);
+ if (!desc_addr)
+ return 0;

mask_bits &= ~PCI_MSIX_ENTRY_CTRL_MASKBIT;
if (flag)
mask_bits |= PCI_MSIX_ENTRY_CTRL_MASKBIT;
- writel(mask_bits, pci_msix_desc_addr(desc) + PCI_MSIX_ENTRY_VECTOR_CTRL);
+
+ writel(mask_bits, desc_addr + PCI_MSIX_ENTRY_VECTOR_CTRL);

return mask_bits;
}
@@ -273,6 +281,11 @@ void __pci_read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
if (entry->msi_attrib.is_msix) {
void __iomem *base = pci_msix_desc_addr(entry);

+ if (!base) {
+ WARN_ON(1);
+ return;
+ }
+
msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
@@ -303,6 +316,9 @@ void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
} else if (entry->msi_attrib.is_msix) {
void __iomem *base = pci_msix_desc_addr(entry);

+ if (!base)
+ goto skip;
+
writel(msg->address_lo, base + PCI_MSIX_ENTRY_LOWER_ADDR);
writel(msg->address_hi, base + PCI_MSIX_ENTRY_UPPER_ADDR);
writel(msg->data, base + PCI_MSIX_ENTRY_DATA);
@@ -327,7 +343,13 @@ void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
msg->data);
}
}
+
+skip:
entry->msg = *msg;
+
+ if (entry->write_msi_msg)
+ entry->write_msi_msg(entry, entry->write_msi_msg_data);
+
}

void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg)
@@ -550,6 +572,7 @@ msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)

entry->msi_attrib.is_msix = 0;
entry->msi_attrib.is_64 = !!(control & PCI_MSI_FLAGS_64BIT);
+ entry->msi_attrib.is_virtual = 0;
entry->msi_attrib.entry_nr = 0;
entry->msi_attrib.maskbit = !!(control & PCI_MSI_FLAGS_MASKBIT);
entry->msi_attrib.default_irq = dev->irq; /* Save IOAPIC IRQ */
@@ -674,6 +697,7 @@ static int msix_setup_entries(struct pci_dev *dev, void __iomem *base,
struct irq_affinity_desc *curmsk, *masks = NULL;
struct msi_desc *entry;
int ret, i;
+ int vec_count = pci_msix_vec_count(dev);

if (affd)
masks = irq_create_affinity_masks(nvec, affd);
@@ -696,6 +720,10 @@ static int msix_setup_entries(struct pci_dev *dev, void __iomem *base,
entry->msi_attrib.entry_nr = entries[i].entry;
else
entry->msi_attrib.entry_nr = i;
+
+ entry->msi_attrib.is_virtual =
+ entry->msi_attrib.entry_nr >= vec_count;
+
entry->msi_attrib.default_irq = dev->irq;
entry->mask_base = base;

@@ -714,12 +742,19 @@ static void msix_program_entries(struct pci_dev *dev,
{
struct msi_desc *entry;
int i = 0;
+ void __iomem *desc_addr;

for_each_pci_msi_entry(entry, dev) {
if (entries)
entries[i++].vector = entry->irq;
- entry->masked = readl(pci_msix_desc_addr(entry) +
- PCI_MSIX_ENTRY_VECTOR_CTRL);
+
+ desc_addr = pci_msix_desc_addr(entry);
+ if (desc_addr)
+ entry->masked = readl(desc_addr +
+ PCI_MSIX_ENTRY_VECTOR_CTRL);
+ else
+ entry->masked = 0;
+
msix_mask_irq(entry, 1);
}
}
@@ -932,7 +967,7 @@ int pci_msix_vec_count(struct pci_dev *dev)
EXPORT_SYMBOL(pci_msix_vec_count);

static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
- int nvec, struct irq_affinity *affd)
+ int nvec, struct irq_affinity *affd, int flags)
{
int nr_entries;
int i, j;
@@ -943,7 +978,7 @@ static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
nr_entries = pci_msix_vec_count(dev);
if (nr_entries < 0)
return nr_entries;
- if (nvec > nr_entries)
+ if (nvec > nr_entries && !(flags & PCI_IRQ_VIRTUAL))
return nr_entries;

if (entries) {
@@ -1079,7 +1114,8 @@ EXPORT_SYMBOL(pci_enable_msi);

static int __pci_enable_msix_range(struct pci_dev *dev,
struct msix_entry *entries, int minvec,
- int maxvec, struct irq_affinity *affd)
+ int maxvec, struct irq_affinity *affd,
+ int flags)
{
int rc, nvec = maxvec;

@@ -1096,7 +1132,7 @@ static int __pci_enable_msix_range(struct pci_dev *dev,
return -ENOSPC;
}

- rc = __pci_enable_msix(dev, entries, nvec, affd);
+ rc = __pci_enable_msix(dev, entries, nvec, affd, flags);
if (rc == 0)
return nvec;

@@ -1127,7 +1163,7 @@ static int __pci_enable_msix_range(struct pci_dev *dev,
int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
int minvec, int maxvec)
{
- return __pci_enable_msix_range(dev, entries, minvec, maxvec, NULL);
+ return __pci_enable_msix_range(dev, entries, minvec, maxvec, NULL, 0);
}
EXPORT_SYMBOL(pci_enable_msix_range);

@@ -1167,7 +1203,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,

if (flags & PCI_IRQ_MSIX) {
msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
- max_vecs, affd);
+ max_vecs, affd, flags);
if (msix_vecs > 0)
return msix_vecs;
}
diff --git a/include/linux/msi.h b/include/linux/msi.h
index 7e9b81c3b50d..c278ae8760df 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -56,6 +56,10 @@ struct fsl_mc_msi_desc {
* @msg: The last set MSI message cached for reuse
* @affinity: Optional pointer to a cpu affinity mask for this descriptor
*
+ * @write_msi_msg: Callback that may be called when the MSI message
+ * address or data changes
+ * @write_msi_msg_data: Data parameter for the callback.
+ *
* @masked: [PCI MSI/X] Mask bits
* @is_msix: [PCI MSI/X] True if MSI-X
* @multiple: [PCI MSI/X] log2 num of messages allocated
@@ -78,6 +82,9 @@ struct msi_desc {
struct msi_msg msg;
struct irq_affinity_desc *affinity;

+ void (*write_msi_msg)(struct msi_desc *entry, void *data);
+ void *write_msi_msg_data;
+
union {
/* PCI MSI/X specific data */
struct {
@@ -88,6 +95,7 @@ struct msi_desc {
u8 multi_cap : 3;
u8 maskbit : 1;
u8 is_64 : 1;
+ u8 is_virtual : 1;
u16 entry_nr;
unsigned default_irq;
} msi_attrib;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 77448215ef5b..c482aaa8e970 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1355,6 +1355,15 @@ int pci_set_vga_state(struct pci_dev *pdev, bool decode,
#define PCI_IRQ_MSI (1 << 1) /* Allow MSI interrupts */
#define PCI_IRQ_MSIX (1 << 2) /* Allow MSI-X interrupts */
#define PCI_IRQ_AFFINITY (1 << 3) /* Auto-assign affinity */
+
+/*
+ * Virtual interrupts allow for more interrupts to be allocated
+ * than the device has interrupts for. These are not programmed
+ * into the device's MSI-X table and must be handled by some
+ * other driver means.
+ */
+#define PCI_IRQ_VIRTUAL (1 << 4)
+
#define PCI_IRQ_ALL_TYPES \
(PCI_IRQ_LEGACY | PCI_IRQ_MSI | PCI_IRQ_MSIX)

--
2.20.1