[xen staging] vpci/msix: improve handling of bogus MSI-X capabilities

[patchbot@xxxxxxx]

commit 53859596c0d34dbca776ec1e47bac8dd90552530
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Fri Sep 26 17:39:29 2025 +0200
Commit:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
CommitDate: Fri Oct 10 11:02:39 2025 +0200

    vpci/msix: improve handling of bogus MSI-X capabilities
    
    I've had the luck to come across a PCI card that exposes a MSI-X capability
    where the BIR of the vector and PBA tables points at a BAR that has 0 size.
    
    This doesn't play nice with the code in vpci_make_msix_hole(), as it would
    still use the address of such empty BAR (0) and attempt to carve a hole in
    the p2m.  This leads to errors like the one below being reported by Xen:
    
    d0v0 0000:22:00.0: existing mapping (mfn: 181c4300 type: 0) at 0 clobbers 
MSIX MMIO area
    
    And the device left unable to enable memory decoding due to the failure
    reported by vpci_make_msix_hole().
    
    Introduce checking in init_msix() to ensure the BARs containing the MSI-X
    tables are usable.  This requires checking that the BIR points to a
    non-empty BAR, and the offset and size of the MSI-X tables can fit in the
    target BAR.
    
    This fixes booting PVH dom0 on Supermicro AS -2126HS-TN servers with AMD
    EPYC 9965 processors.  The broken device is:
    
    22:00.0 SATA controller: Advanced Micro Devices, Inc. [AMD] FCH SATA 
Controller [AHCI mode] (rev 93)
    
    There are multiple of those integrated controllers in the system, all
    broken in the same way.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Released-Acked-By: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
    Reviewed-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
 xen/drivers/vpci/msix.c | 51 ++++++++++++++++++++++++++++++++++++++++++++-----
 xen/include/xen/lib.h   |  3 +++
 2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
index 54a5070733..032e471bb1 100644
--- a/xen/drivers/vpci/msix.c
+++ b/xen/drivers/vpci/msix.c
@@ -18,6 +18,7 @@
  */
 
 #include <xen/io.h>
+#include <xen/lib.h>
 #include <xen/sched.h>
 #include <xen/vpci.h>
 
@@ -675,6 +676,51 @@ static int cf_check init_msix(struct pci_dev *pdev)
     if ( !msix )
         return -ENOMEM;
 
+    msix->tables[VPCI_MSIX_TABLE] =
+        pci_conf_read32(pdev->sbdf, msix_table_offset_reg(msix_offset));
+    msix->tables[VPCI_MSIX_PBA] =
+        pci_conf_read32(pdev->sbdf, msix_pba_offset_reg(msix_offset));
+
+    /* Check that the referenced BAR(s) regions are valid. */
+    for ( i = 0; i < ARRAY_SIZE(msix->tables); i++ )
+    {
+        const char *name = (i == VPCI_MSIX_TABLE) ? "vector" : "PBA";
+        const struct vpci_bar *bars = pdev->vpci->header.bars;
+        unsigned int bir = msix->tables[i] & PCI_MSIX_BIRMASK;
+        unsigned int type;
+        unsigned int offset = msix->tables[i] & ~PCI_MSIX_BIRMASK;
+        unsigned int size =
+            (i == VPCI_MSIX_TABLE) ? max_entries * PCI_MSIX_ENTRY_SIZE
+                                   : ROUNDUP(DIV_ROUND_UP(max_entries, 8), 8);
+
+        if ( bir >= ARRAY_SIZE(pdev->vpci->header.bars) )
+        {
+            printk(XENLOG_ERR DEV_BUG_PREFIX
+                   "%pp: MSI-X %s table with out of range BIR %u\n",
+                   &pdev->sbdf, name, bir);
+ invalid:
+            xfree(msix);
+            return -ENODEV;
+        }
+
+        type = bars[bir].type;
+        if ( type != VPCI_BAR_MEM32 && type != VPCI_BAR_MEM64_LO )
+        {
+            printk(XENLOG_ERR DEV_BUG_PREFIX
+                   "%pp: MSI-X %s table at invalid BAR%u with type %u\n",
+                   &pdev->sbdf, name, bir, type);
+            goto invalid;
+        }
+
+        if ( (uint64_t)offset + size > bars[bir].size )
+        {
+            printk(XENLOG_ERR DEV_BUG_PREFIX
+                   "%pp: MSI-X %s table offset %#x size %#x outside of BAR%u 
size %#lx\n",
+                   &pdev->sbdf, name, offset, size, bir, bars[bir].size);
+            goto invalid;
+        }
+    }
+
     rc = vpci_add_register(pdev->vpci, control_read, control_write,
                            msix_control_reg(msix_offset), 2, msix);
     if ( rc )
@@ -686,11 +732,6 @@ static int cf_check init_msix(struct pci_dev *pdev)
     msix->max_entries = max_entries;
     msix->pdev = pdev;
 
-    msix->tables[VPCI_MSIX_TABLE] =
-        pci_conf_read32(pdev->sbdf, msix_table_offset_reg(msix_offset));
-    msix->tables[VPCI_MSIX_PBA] =
-        pci_conf_read32(pdev->sbdf, msix_pba_offset_reg(msix_offset));
-
     for ( i = 0; i < max_entries; i++)
     {
         msix->entries[i].masked = true;
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index c434dd5f16..c4ac482392 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -60,6 +60,9 @@ static inline void
 debugtrace_printk(const char *fmt, ...) {}
 #endif
 
+/* Common log prefixes for platform related issues. */
+#define DEV_BUG_PREFIX "DEVICE BUG: "
+
 extern void printk(const char *fmt, ...)
     __attribute__ ((format (printf, 1, 2), cold));
 void vprintk(const char *fmt, va_list args)
--
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