[Xen-devel] [PATCH v6 3/8] x86/PCI: read maximum MSI vector count early

[Jan Beulich <jbeulich@xxxxxxxx>]

Rather than doing this every time we set up interrupts for a device
anew (and then in several places) fill this invariant field right after
allocating struct pci_dev.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v6: New.

---
 xen/arch/x86/msi.c            |   13 +++++--------
 xen/drivers/passthrough/pci.c |   10 ++++++++++
 xen/drivers/vpci/msi.c        |    9 ++++-----
 xen/include/xen/pci.h         |    3 ++-
 xen/include/xen/vpci.h        |    6 ++----
 5 files changed, 23 insertions(+), 18 deletions(-)

--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -664,7 +664,7 @@ static int msi_capability_init(struct pc
 {
     struct msi_desc *entry;
     int pos;
-    unsigned int i, maxvec, mpos;
+    unsigned int i, mpos;
     u16 control, seg = dev->seg;
     u8 bus = dev->bus;
     u8 slot = PCI_SLOT(dev->devfn);
@@ -675,9 +675,8 @@ static int msi_capability_init(struct pc
     if ( !pos )
         return -ENODEV;
     control = pci_conf_read16(dev->sbdf, msi_control_reg(pos));
-    maxvec = multi_msi_capable(control);
-    if ( nvec > maxvec )
-        return maxvec;
+    if ( nvec > dev->msi_maxvec )
+        return dev->msi_maxvec;
     control &= ~PCI_MSI_FLAGS_QSIZE;
     multi_msi_enable(control, nvec);
 
@@ -711,7 +710,7 @@ static int msi_capability_init(struct pc
 
         /* All MSIs are unmasked by default, Mask them all */
         maskbits = pci_conf_read32(dev->sbdf, mpos);
-        maskbits |= ~(u32)0 >> (32 - maxvec);
+        maskbits |= ~(u32)0 >> (32 - dev->msi_maxvec);
         pci_conf_write32(dev->sbdf, mpos, maskbits);
     }
     list_add_tail(&entry->list, &dev->msi_list);
@@ -1284,7 +1283,6 @@ int pci_msi_conf_write_intercept(struct
     entry = find_msi_entry(pdev, -1, PCI_CAP_ID_MSI);
     if ( entry && entry->msi_attrib.maskbit )
     {
-        uint16_t cntl;
         uint32_t unused;
         unsigned int nvec = entry->msi.nvec;
 
@@ -1297,8 +1295,7 @@ int pci_msi_conf_write_intercept(struct
         if ( reg < entry->msi.mpos || reg >= entry->msi.mpos + 4 || size != 4 )
             return -EACCES;
 
-        cntl = pci_conf_read16(pdev->sbdf, msi_control_reg(pos));
-        unused = ~(uint32_t)0 >> (32 - multi_msi_capable(cntl));
+        unused = ~(uint32_t)0 >> (32 - pdev->msi_maxvec);
         for ( pos = 0; pos < nvec; ++pos, ++entry )
         {
             entry->msi_attrib.guest_masked =
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -340,6 +340,16 @@ static struct pci_dev *alloc_pdev(struct
     pdev->domain = NULL;
     INIT_LIST_HEAD(&pdev->msi_list);
 
+
+    pos = pci_find_cap_offset(pseg->nr, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
+                              PCI_CAP_ID_MSI);
+    if ( pos )
+    {
+        uint16_t ctrl = pci_conf_read16(pdev->sbdf, msi_control_reg(pos));
+
+        pdev->msi_maxvec = multi_msi_capable(ctrl);
+    }
+
     pos = pci_find_cap_offset(pseg->nr, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
                               PCI_CAP_ID_MSIX);
     if ( pos )
--- a/xen/drivers/vpci/msi.c
+++ b/xen/drivers/vpci/msi.c
@@ -27,7 +27,7 @@ static uint32_t control_read(const struc
 {
     const struct vpci_msi *msi = data;
 
-    return MASK_INSR(fls(msi->max_vectors) - 1, PCI_MSI_FLAGS_QMASK) |
+    return MASK_INSR(fls(pdev->msi_maxvec) - 1, PCI_MSI_FLAGS_QMASK) |
            MASK_INSR(fls(msi->vectors) - 1, PCI_MSI_FLAGS_QSIZE) |
            (msi->enabled ? PCI_MSI_FLAGS_ENABLE : 0) |
            (msi->masking ? PCI_MSI_FLAGS_MASKBIT : 0) |
@@ -40,7 +40,7 @@ static void control_write(const struct p
     struct vpci_msi *msi = data;
     unsigned int vectors = min_t(uint8_t,
                                  1u << MASK_EXTR(val, PCI_MSI_FLAGS_QSIZE),
-                                 msi->max_vectors);
+                                 pdev->msi_maxvec);
     bool new_enabled = val & PCI_MSI_FLAGS_ENABLE;
 
     /*
@@ -215,8 +215,7 @@ static int init_msi(struct pci_dev *pdev
      * FIXME: I've only been able to test this code with devices using a single
      * MSI interrupt and no mask register.
      */
-    pdev->vpci->msi->max_vectors = multi_msi_capable(control);
-    ASSERT(pdev->vpci->msi->max_vectors <= 32);
+    ASSERT(pdev->msi_maxvec <= 32);
 
     /* The multiple message enable is 0 after reset (1 message enabled). */
     pdev->vpci->msi->vectors = 1;
@@ -298,7 +297,7 @@ void vpci_dump_msi(void)
                 if ( msi->masking )
                     printk(" mask=%08x", msi->mask);
                 printk(" vectors max: %u enabled: %u\n",
-                       msi->max_vectors, msi->vectors);
+                       pdev->msi_maxvec, msi->vectors);
 
                 vpci_msi_arch_print(msi);
             }
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -94,7 +94,8 @@ struct pci_dev {
         pci_sbdf_t sbdf;
     };
 
-    u8 phantom_stride;
+    uint8_t msi_maxvec;
+    uint8_t phantom_stride;
 
     nodeid_t node; /* NUMA node */
 
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -99,14 +99,12 @@ struct vpci {
         uint32_t mask;
         /* Data. */
         uint16_t data;
-        /* Maximum number of vectors supported by the device. */
-        uint8_t max_vectors : 6;
+        /* Number of vectors configured. */
+        uint8_t vectors     : 6;
         /* Supports per-vector masking? */
         bool masking        : 1;
         /* 64-bit address capable? */
         bool address64      : 1;
-        /* Number of vectors configured. */
-        uint8_t vectors     : 6;
         /* Enabled? */
         bool enabled        : 1;
         /* Arch-specific data. */


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