[Xen-devel] RE: [PATCH] VT-d: don't reject possibly valid DRHD or RMRR

["Kay, Allen M" <allen.m.kay@xxxxxxxxx>]

For RMRR case, looks like you miss the following change (or something similar):

-for ( i = 0; i < rmrru->scope.devices_cnt; i++ )
+for (; i < rmrru->scope.devices_cnt; i++ )

Otherwise, the logic for handling non-zero PCI segments looks reasonable.

Allen

-----Original Message-----
From: Jan Beulich [mailto:JBeulich@xxxxxxxx] 
Sent: Tuesday, October 04, 2011 4:30 AM
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Kay, Allen M
Subject: [PATCH] VT-d: don't reject possibly valid DRHD or RMRR

If a non-zero PCI segment isn't accessible during Xen boot (because
firmware decided to not enter the necessary MMIO space into the E820
table), devices referred to on those segments through DRHD or RMRR
structures should not be rejected just because the devices can't be
found.

This is in line with what is being done in at least one other case
already: Systems with more than one PCI segment (usually high end
ones) are assumed to have valid firmware provided data, while systems
with just segment 0 continue to have their firmware tables validated.

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

--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -53,6 +53,11 @@ static inline struct pci_seg *get_pseg(u
     return radix_tree_lookup(&pci_segments, seg);
 }
 
+bool_t pci_known_segment(u16 seg)
+{
+    return get_pseg(seg) != NULL;
+}
+
 static struct pci_seg *alloc_pseg(u16 seg)
 {
     struct pci_seg *pseg = get_pseg(seg);
--- a/xen/drivers/passthrough/vtd/dmar.c
+++ b/xen/drivers/passthrough/vtd/dmar.c
@@ -444,10 +444,14 @@ acpi_parse_one_drhd(struct acpi_dmar_ent
     else
     {
         u8 b, d, f;
-        int i, invalid_cnt = 0;
+        unsigned int i = 0, invalid_cnt = 0;
         void *p;
 
-        for ( i = 0, p = dev_scope_start; i < dmaru->scope.devices_cnt;
+        /* Skip checking if segment is not accessible yet. */
+        if ( !pci_known_segment(drhd->segment) )
+            i = UINT_MAX;
+
+        for ( p = dev_scope_start; i < dmaru->scope.devices_cnt;
               i++, p += ((struct acpi_dev_scope *)p)->length )
         {
             if ( ((struct acpi_dev_scope *)p)->dev_type == ACPI_DEV_IOAPIC ||
@@ -549,7 +553,12 @@ acpi_parse_one_rmrr(struct acpi_dmar_ent
     else
     {
         u8 b, d, f;
-        int i, ignore = 0;
+        bool_t ignore = 0;
+        unsigned int i = 0;
+
+        /* Skip checking if segment is not accessible yet. */
+        if ( !pci_known_segment(rmrr->segment) )
+            i = UINT_MAX;
 
         for ( i = 0; i < rmrru->scope.devices_cnt; i++ )
         {
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -82,6 +82,7 @@ enum {
     DEV_TYPE_PCI,
 };
 
+bool_t pci_known_segment(u16 seg);
 int pci_device_detect(u16 seg, u8 bus, u8 dev, u8 func);
 int scan_pci_devices(void);
 int pdev_type(u16 seg, u8 bus, u8 devfn);




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