passthrough: allow to suppress SERR and PERR signaling altogether

This is just to have a workaround at hand in case other chipsets (not
covered by the previous two patches) also have similar issues.

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

--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -154,6 +154,112 @@ static void __init parse_phantom_dev(cha
 }
 custom_param("pci-phantom", parse_phantom_dev);
 
+static u16 __read_mostly command_mask;
+static u16 __read_mostly bridge_ctl_mask;
+
+/*
+ * The 'pci' parameter controls certain PCI device aspects.
+ * Optional comma separated value may contain:
+ *
+ *   serr                       don't suppress system errors (default)
+ *   no-serr                    suppress system errors
+ *   perr                       don't suppress parity errors (default)
+ *   no-perr                    suppress parity errors
+ */
+static void __init parse_pci_param(char *s)
+{
+    char *ss;
+
+    do {
+        bool_t on = !!strncmp(s, "no-", 3);
+        u16 cmd_mask = 0, brctl_mask = 0;
+
+        if ( !on )
+            s += 3;
+
+        ss = strchr(s, ',');
+        if ( ss )
+            *ss = '\0';
+
+        if ( !strcmp(s, "serr") )
+        {
+            cmd_mask = PCI_COMMAND_SERR;
+            brctl_mask = PCI_BRIDGE_CTL_SERR | PCI_BRIDGE_CTL_DTMR_SERR;
+        }
+        else if ( !strcmp(s, "perr") )
+        {
+            cmd_mask = PCI_COMMAND_PARITY;
+            brctl_mask = PCI_BRIDGE_CTL_PARITY;
+        }
+
+        if ( on )
+        {
+            command_mask &= ~cmd_mask;
+            bridge_ctl_mask &= ~brctl_mask;
+        }
+        else
+        {
+            command_mask |= cmd_mask;
+            bridge_ctl_mask |= brctl_mask;
+        }
+
+        s = ss + 1;
+    } while ( ss );
+}
+custom_param("pci", parse_pci_param);
+
+static void check_pdev(const struct pci_dev *pdev)
+{
+#define PCI_STATUS_CHECK \
+    (PCI_STATUS_PARITY | PCI_STATUS_SIG_TARGET_ABORT | \
+     PCI_STATUS_REC_TARGET_ABORT | PCI_STATUS_REC_MASTER_ABORT | \
+     PCI_STATUS_SIG_SYSTEM_ERROR | PCI_STATUS_DETECTED_PARITY)
+    u16 seg = pdev->seg;
+    u8 bus = pdev->bus;
+    u8 dev = PCI_SLOT(pdev->devfn);
+    u8 func = PCI_FUNC(pdev->devfn);
+    u16 val;
+
+    if ( command_mask )
+    {
+        val = pci_conf_read16(seg, bus, dev, func, PCI_COMMAND);
+        if ( val & command_mask )
+            pci_conf_write16(seg, bus, dev, func, PCI_COMMAND,
+                             val & ~command_mask);
+        val = pci_conf_read16(seg, bus, dev, func, PCI_STATUS);
+        if ( val & PCI_STATUS_CHECK )
+        {
+            printk(XENLOG_INFO "%04x:%02x:%02x.%u status %04x\n",
+                   seg, bus, dev, func, val);
+            pci_conf_write16(seg, bus, dev, func, PCI_STATUS, val);
+        }
+    }
+
+    switch ( pci_conf_read8(seg, bus, dev, func, PCI_HEADER_TYPE) & 0x7f )
+    {
+    case PCI_HEADER_TYPE_BRIDGE:
+        if ( !bridge_ctl_mask )
+            break;
+        val = pci_conf_read16(seg, bus, dev, func, PCI_BRIDGE_CONTROL);
+        if ( val & bridge_ctl_mask )
+            pci_conf_write16(seg, bus, dev, func, PCI_BRIDGE_CONTROL,
+                             val & ~bridge_ctl_mask);
+        val = pci_conf_read16(seg, bus, dev, func, PCI_SEC_STATUS);
+        if ( val & PCI_STATUS_CHECK )
+        {
+            printk(XENLOG_INFO "%04x:%02x:%02x.%u secondary status %04x\n",
+                   seg, bus, dev, func, val);
+            pci_conf_write16(seg, bus, dev, func, PCI_SEC_STATUS, val);
+        }
+        break;
+
+    case PCI_HEADER_TYPE_CARDBUS:
+        /* TODO */
+        break;
+    }
+#undef PCI_STATUS_CHECK
+}
+
 static struct pci_dev *alloc_pdev(struct pci_seg *pseg, u8 bus, u8 devfn)
 {
     struct pci_dev *pdev;
@@ -252,6 +358,8 @@ static struct pci_dev *alloc_pdev(struct
             break;
     }
 
+    check_pdev(pdev);
+
     return pdev;
 }
 
@@ -566,6 +674,8 @@ int pci_add_device(u16 seg, u8 bus, u8 d
                    seg, bus, slot, func, ctrl);
     }
 
+    check_pdev(pdev);
+
     ret = 0;
     if ( !pdev->domain )
     {
--- a/xen/include/xen/pci_regs.h
+++ b/xen/include/xen/pci_regs.h
@@ -125,7 +125,7 @@
 #define  PCI_IO_RANGE_TYPE_16	0x00
 #define  PCI_IO_RANGE_TYPE_32	0x01
 #define  PCI_IO_RANGE_MASK	(~0x0fUL)
-#define PCI_SEC_STATUS		0x1e	/* Secondary status register, only bit 14 used */
+#define PCI_SEC_STATUS		0x1e	/* Secondary status register */
 #define PCI_MEMORY_BASE		0x20	/* Memory range behind */
 #define PCI_MEMORY_LIMIT	0x22
 #define  PCI_MEMORY_RANGE_TYPE_MASK 0x0fUL
@@ -152,6 +152,7 @@
 #define  PCI_BRIDGE_CTL_MASTER_ABORT	0x20  /* Report master aborts */
 #define  PCI_BRIDGE_CTL_BUS_RESET	0x40	/* Secondary bus reset */
 #define  PCI_BRIDGE_CTL_FAST_BACK	0x80	/* Fast Back2Back enabled on secondary interface */
+#define  PCI_BRIDGE_CTL_DTMR_SERR	0x800	/* SERR upon discard timer expiry */
 
 /* Header type 2 (CardBus bridges) */
 #define PCI_CB_CAPABILITY_LIST	0x14