[Xen-devel] [PATCH 6/6] vpci/msix: carve p2m hole for MSIX MMIO regions

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Make sure the MSIX MMIO regions don't have p2m entries setup, so that
accesses to them trap into the hypervisor and can be handled by vpci.

This is a side-effect of commit 042678762 for PVH Dom0, which added
mappings for all the reserved regions into the Dom0 p2m.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/drivers/vpci/header.c |  8 ++++++++
 xen/drivers/vpci/msix.c   | 40 +++++++++++++++++++++++++++++++++++++++
 xen/include/xen/vpci.h    |  3 +++
 3 files changed, 51 insertions(+)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 7a1380a5e7..68cd91c0ec 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -88,6 +88,14 @@ static void modify_decoding(const struct pci_dev *pdev, bool 
map, bool rom_only)
     uint16_t cmd;
     unsigned int i;
 
+    /*
+     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
+     * can be trapped (and emulated) by Xen when the memory decoding bit is
+     * enabled.
+     */
+    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
+        return;
+
     for ( i = 0; i < ARRAY_SIZE(header->bars); i++ )
     {
         if ( !MAPPABLE_BAR(&header->bars[i]) )
diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
index 1960dae123..5759551724 100644
--- a/xen/drivers/vpci/msix.c
+++ b/xen/drivers/vpci/msix.c
@@ -21,6 +21,7 @@
 #include <xen/vpci.h>
 
 #include <asm/msi.h>
+#include <asm/p2m.h>
 
 #define VMSIX_SIZE(num) offsetof(struct vpci_msix, entries[num])
 
@@ -395,6 +396,45 @@ static const struct hvm_mmio_ops vpci_msix_table_ops = {
     .write = msix_write,
 };
 
+int vpci_make_msix_hole(const struct pci_dev *pdev)
+{
+    struct domain *d = pdev->domain;
+    unsigned int i;
+
+    if ( !pdev->vpci->msix )
+        return 0;
+
+    /* Make sure there's a hole for the MSIX table/PBA in the p2m. */
+    for ( i = 0; i < ARRAY_SIZE(pdev->vpci->msix->tables); i++ )
+    {
+        unsigned long start = PFN_DOWN(vmsix_table_addr(pdev->vpci, i));
+        unsigned long end = PFN_DOWN(vmsix_table_addr(pdev->vpci, i) +
+                                     vmsix_table_size(pdev->vpci, i) - 1);
+
+        for ( ; start <= end; start++ )
+        {
+            p2m_type_t t;
+            mfn_t mfn = get_gfn_query(d, start, &t);
+
+            if ( t == p2m_mmio_direct && mfn_x(mfn) == start )
+                    clear_identity_p2m_entry(d, start);
+            else if ( t != p2m_mmio_dm )
+            {
+                put_gfn(d, start);
+                gprintk(XENLOG_WARNING,
+                        "%04x:%02x:%02x.%u: existing mapping (mfn: %" PRI_mfn
+                        "type: %d) at %#lx clobbers MSIX MMIO area\n",
+                        pdev->seg, pdev->bus, PCI_SLOT(pdev->devfn),
+                        PCI_FUNC(pdev->devfn), mfn_x(mfn), t, start);
+                return -EEXIST;
+            }
+            put_gfn(d, start);
+        }
+    }
+
+    return 0;
+}
+
 static int init_msix(struct pci_dev *pdev)
 {
     struct domain *d = pdev->domain;
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index df0537f523..c7ddc7e63d 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -152,6 +152,9 @@ struct vpci_vcpu {
 #ifdef __XEN__
 void vpci_dump_msi(void);
 
+/* Make sure there's a hole in the p2m for the MSIX mmio areas. */
+int vpci_make_msix_hole(const struct pci_dev *pdev);
+
 /* Arch-specific vPCI MSI helpers. */
 void vpci_msi_arch_mask(struct vpci_msi *msi, const struct pci_dev *pdev,
                         unsigned int entry, bool mask);
-- 
2.19.0


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