x86/vMSI: miscellaneous fixes

This addresses a number of problems in msixtbl_{read,write}():
- address alignment was not checked, allowing for memory corruption in
  the hypervisor (write case) or returning of hypervisor private data
  to the guest (read case)
- the interrupt mask bit was permitted to be written by the guest
  (while Xen's interrupt flow control routines need to control it)
- MAX_MSIX_TABLE_{ENTRIES,PAGES} were pointlessly defined to plain
  numbers (making it unobvious why they have these values, and making
  the latter non-portable)
- MAX_MSIX_TABLE_PAGES was also off by one (failing to account for a
  non-zero table offset); this was also affecting host MSI-X code
- struct msixtbl_entry's table_flags[] was one element larger than
  necessary due to improper open-coding of BITS_TO_LONGS()
- msixtbl_read() unconditionally accessed the physical table, even
  though the data was only needed in a quarter of all cases
- various calculations were done unnecessarily for both of the rather
  distinct code paths in msixtbl_read()

Additionally it is unclear on what basis MAX_MSIX_ACC_ENTRIES was
chosen to be 3.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Committed-by: Keir Fraser <keir@xen.org>
xen-unstable changeset:   24535:fb81b807c154
xen-unstable date:        Mon Jan 23 09:35:17 2012 +0000

4 files changed, 37 insertions, 22 deletions

diff --git a/xen/arch/x86/hvm/vmsi.c b/xen/arch/x86/hvm/vmsi.c
index d9ec9fb0a4..87f3bd1396 100644
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -157,7 +157,7 @@ struct msixtbl_entry
     struct pci_dev *pdev;
     unsigned long gtable;       /* gpa of msix table */
     unsigned long table_len;
-    unsigned long table_flags[MAX_MSIX_TABLE_ENTRIES / BITS_PER_LONG + 1];
+    unsigned long table_flags[BITS_TO_LONGS(MAX_MSIX_TABLE_ENTRIES)];
 
     struct rcu_head rcu;
 };
@@ -179,17 +179,14 @@ static struct msixtbl_entry *msixtbl_find_entry(
 static void __iomem *msixtbl_addr_to_virt(
     struct msixtbl_entry *entry, unsigned long addr)
 {
-    int idx, nr_page;
+    unsigned int idx, nr_page;
 
-    if ( !entry )
+    if ( !entry || !entry->pdev )
         return NULL;
 
     nr_page = (addr >> PAGE_SHIFT) -
               (entry->gtable >> PAGE_SHIFT);
 
-    if ( !entry->pdev )
-        return NULL;
-
     idx = entry->pdev->msix_table_idx[nr_page];
     if ( !idx )
         return NULL;
@@ -207,10 +204,10 @@ static int msixtbl_read(
     void *virt;
     int r = X86EMUL_UNHANDLEABLE;
 
-    rcu_read_lock();
+    if ( len != 4 || (address & 3) )
+        return r;
 
-    if ( len != 4 )
-        goto out;
+    rcu_read_lock();
 
     offset = address & (PCI_MSIX_ENTRY_SIZE - 1);
     if ( offset != PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET)
@@ -235,13 +232,13 @@ static int msixtbl_write(struct vcpu *v, unsigned long address,
     unsigned long offset;
     struct msixtbl_entry *entry;
     void *virt;
-    int nr_entry;
+    unsigned int nr_entry;
     int r = X86EMUL_UNHANDLEABLE;
 
-    rcu_read_lock();
+    if ( len != 4 || (address & 3) )
+        return r;
 
-    if ( len != 4 )
-        goto out;
+    rcu_read_lock();
 
     entry = msixtbl_find_entry(v, address);
     nr_entry = (address - entry->gtable) / PCI_MSIX_ENTRY_SIZE;
@@ -261,9 +258,22 @@ static int msixtbl_write(struct vcpu *v, unsigned long address,
     if ( !virt )
         goto out;
 
+    /* Do not allow the mask bit to be changed. */
+#if 0 /* XXX
+       * As the mask bit is the only defined bit in the word, and as the
+       * host MSI-X code doesn't preserve the other bits anyway, doing
+       * this is pointless. So for now just discard the write (also
+       * saving us from having to determine the matching irq_desc).
+       */
+    spin_lock_irqsave(&desc->lock, flags);
+    orig = readl(virt);
+    val &= ~PCI_MSIX_VECTOR_BITMASK;
+    val |= orig & PCI_MSIX_VECTOR_BITMASK;
     writel(val, virt);
-    r = X86EMUL_OKAY;
+    spin_unlock_irqrestore(&desc->lock, flags);
+#endif
 
+    r = X86EMUL_OKAY;
 out:
     rcu_read_unlock();
     return r;
diff --git a/xen/include/asm-x86/msi.h b/xen/include/asm-x86/msi.h
index bc8ab0e870..75e73dd259 100644
--- a/xen/include/asm-x86/msi.h
+++ b/xen/include/asm-x86/msi.h
@@ -127,12 +127,6 @@ extern const struct hw_interrupt_type pci_msi_type;
 #define PCI_MSIX_FLAGS_BIRMASK		(7 << 0)
 #define PCI_MSIX_FLAGS_BITMASK		(1 << 0)
 
-#define PCI_MSIX_ENTRY_SIZE			16
-#define  PCI_MSIX_ENTRY_LOWER_ADDR_OFFSET	0
-#define  PCI_MSIX_ENTRY_UPPER_ADDR_OFFSET	4
-#define  PCI_MSIX_ENTRY_DATA_OFFSET		8
-#define  PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET	12
-
 #define msi_control_reg(base)		(base + PCI_MSI_FLAGS)
 #define msi_lower_address_reg(base)	(base + PCI_MSI_ADDRESS_LO)
 #define msi_upper_address_reg(base)	(base + PCI_MSI_ADDRESS_HI)
diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
index 2f2014fd64..634ed106d8 100644
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -11,6 +11,8 @@
 #include <xen/types.h>
 #include <xen/list.h>
 #include <xen/spinlock.h>
+#include <xen/pci_regs.h>
+#include <asm/page.h>
 
 /*
  * The PCI interface treats multi-function devices as independent
@@ -29,8 +31,10 @@
 #define PCI_BDF(b,d,f)  ((((b) & 0xff) << 8) | PCI_DEVFN(d,f))
 #define PCI_BDF2(b,df)  ((((b) & 0xff) << 8) | ((df) & 0xff))
 
-#define MAX_MSIX_TABLE_ENTRIES  2048
-#define MAX_MSIX_TABLE_PAGES    8
+#define MAX_MSIX_TABLE_ENTRIES  (PCI_MSIX_FLAGS_QSIZE + 1)
+#define MAX_MSIX_TABLE_PAGES    PFN_UP(MAX_MSIX_TABLE_ENTRIES * \
+                                       PCI_MSIX_ENTRY_SIZE + \
+                                       (~PCI_MSIX_FLAGS_BIRMASK & (PAGE_SIZE - 1)))
 struct pci_dev_info {
     unsigned is_extfn;
     unsigned is_virtfn;
diff --git a/xen/include/xen/pci_regs.h b/xen/include/xen/pci_regs.h
index b92a171052..8bd193a5d7 100644
--- a/xen/include/xen/pci_regs.h
+++ b/xen/include/xen/pci_regs.h
@@ -302,6 +302,13 @@
 #define  PCI_MSIX_FLAGS_ENABLE	(1 << 15)
 #define  PCI_MSIX_FLAGS_MASKALL	(1 << 14)
 #define PCI_MSIX_FLAGS_BIRMASK	(7 << 0)
+
+#define PCI_MSIX_ENTRY_SIZE			16
+#define  PCI_MSIX_ENTRY_LOWER_ADDR_OFFSET	0
+#define  PCI_MSIX_ENTRY_UPPER_ADDR_OFFSET	4
+#define  PCI_MSIX_ENTRY_DATA_OFFSET		8
+#define  PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET	12
+
 #define PCI_MSIX_FLAGS_BITMASK	(1 << 0)
 
 /* CompactPCI Hotswap Register */