x86/msi: get rid of read_msi_msg

It's safer and faster to just use the cached last written
(untranslated) MSI message stored in msi_desc for the single user that
calls read_msi_msg.

This also prevents relying on the data read from the device MSI
registers in order to figure out the index into the IOMMU interrupt
remapping table, which is not safe.

This is part of XSA-337.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 475881ed89f444ff01a8758b151afeab1c343e40..8c5fac1f69232a573d22124c72f797039e1ee2ef 100644 (file)
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -191,59 +191,6 @@ void msi_compose_msg(unsigned vector, const cpumask_t *cpu_mask, struct msi_msg
                 MSI_DATA_VECTOR(vector);
 }
 
-static bool read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
-{
-    switch ( entry->msi_attrib.type )
-    {
-    case PCI_CAP_ID_MSI:
-    {
-        struct pci_dev *dev = entry->dev;
-        int pos = entry->msi_attrib.pos;
-        u16 data, seg = dev->seg;
-        u8 bus = dev->bus;
-        u8 slot = PCI_SLOT(dev->devfn);
-        u8 func = PCI_FUNC(dev->devfn);
-
-        msg->address_lo = pci_conf_read32(seg, bus, slot, func,
-                                          msi_lower_address_reg(pos));
-        if ( entry->msi_attrib.is_64 )
-        {
-            msg->address_hi = pci_conf_read32(seg, bus, slot, func,
-                                              msi_upper_address_reg(pos));
-            data = pci_conf_read16(seg, bus, slot, func,
-                                   msi_data_reg(pos, 1));
-        }
-        else
-        {
-            msg->address_hi = 0;
-            data = pci_conf_read16(seg, bus, slot, func,
-                                   msi_data_reg(pos, 0));
-        }
-        msg->data = data;
-        break;
-    }
-    case PCI_CAP_ID_MSIX:
-    {
-        void __iomem *base = entry->mask_base;
-
-        if ( unlikely(!msix_memory_decoded(entry->dev,
-                                           entry->msi_attrib.pos)) )
-            return false;
-        msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR_OFFSET);
-        msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR_OFFSET);
-        msg->data = readl(base + PCI_MSIX_ENTRY_DATA_OFFSET);
-        break;
-    }
-    default:
-        BUG();
-    }
-
-    if ( iommu_intremap )
-        iommu_read_msi_from_ire(entry, msg);
-
-    return true;
-}
-
 static int write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 {
     entry->msg = *msg;
@@ -321,10 +268,7 @@ void set_msi_affinity(struct irq_desc *desc, const cpumask_t *mask)
 
     ASSERT(spin_is_locked(&desc->lock));
 
-    memset(&msg, 0, sizeof(msg));
-    if ( !read_msi_msg(msi_desc, &msg) )
-        return;
-
+    msg = msi_desc->msg;
     msg.data &= ~MSI_DATA_VECTOR_MASK;
     msg.data |= MSI_DATA_VECTOR(desc->arch.vector);
     msg.address_lo &= ~MSI_ADDR_DEST_ID_MASK;