[xen staging] drivers/char: mark extra reserved device memory in memory map

[patchbot@xxxxxxx]

commit dd5101a6169f89b9e3f3b72f0b0fcdb38db2fb35
Author:     Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
AuthorDate: Wed Apr 3 09:34:22 2024 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Apr 3 09:34:22 2024 +0200

    drivers/char: mark extra reserved device memory in memory map
    
    The IOMMU driver checks if RMRR/IVMD are marked as reserved in memory
    map. This should be true for addresses coming from the firmware, but
    when extra pages used by Xen itself are included in the mapping, those
    are taken from usable RAM used. Mark those pages as reserved too.
    
    Not marking the pages as reserved didn't caused issues before due to
    another a bug in IOMMU driver code, that was fixed in 83afa3135830
    ("amd-vi: fix IVMD memory type checks").
    
    Failing to reserve memory will lead to panic in IOMMU setup code. And
    not including the page in IOMMU mapping will lead to broken console (due
    to IOMMU faults). The pages chosen by the XHCI console driver should
    still be usable by the CPU though, and the console code already can deal
    with too slow console by dropping characters (and console not printing
    anything is a special case of "slow"). When reserving fails print an error
    message showing which pages failed and who requested them. This should
    be enough hint to find why XHCI console doesn't work.
    
    Fixes: 3a1a7b809ffa "drivers/char: mark DMA buffers as reserved for the 
XHCI"
    Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/passthrough/iommu.c | 17 +++++++++++++++++
 xen/include/xen/iommu.h         |  5 ++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 03587c0cd6..ba18136c46 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -22,6 +22,10 @@
 #include <xen/keyhandler.h>
 #include <xsm/xsm.h>
 
+#ifdef CONFIG_X86
+#include <asm/e820.h>
+#endif
+
 unsigned int __read_mostly iommu_dev_iotlb_timeout = 1000;
 integer_param("iommu_dev_iotlb_timeout", iommu_dev_iotlb_timeout);
 
@@ -715,6 +719,19 @@ int __init 
iommu_get_extra_reserved_device_memory(iommu_grdm_t *func,
 
     for ( idx = 0; idx < nr_extra_reserved_ranges; idx++ )
     {
+#ifdef CONFIG_X86
+        paddr_t start = pfn_to_paddr(extra_reserved_ranges[idx].start);
+        paddr_t end = pfn_to_paddr(extra_reserved_ranges[idx].start +
+                                   extra_reserved_ranges[idx].nr);
+
+        if ( !reserve_e820_ram(&e820, start, end) )
+        {
+            printk(XENLOG_ERR "Failed to reserve [%"PRIx64"-%"PRIx64") for %s, 
"
+                   "skipping IOMMU mapping for it, some functionality may be 
broken\n",
+                   start, end, extra_reserved_ranges[idx].name);
+            continue;
+        }
+#endif
         ret = func(extra_reserved_ranges[idx].start,
                    extra_reserved_ranges[idx].nr,
                    extra_reserved_ranges[idx].sbdf.sbdf,
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index a9c9457c07..92db6f124f 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -321,7 +321,8 @@ struct iommu_ops {
 };
 
 /*
- * To be called by Xen internally, to register extra RMRR/IVMD ranges.
+ * To be called by Xen internally, to register extra RMRR/IVMD ranges for RAM
+ * pages.
  * Needs to be called before IOMMU initialization.
  */
 extern int iommu_add_extra_reserved_device_memory(unsigned long start,
@@ -331,6 +332,8 @@ extern int iommu_add_extra_reserved_device_memory(unsigned 
long start,
 /*
  * To be called by specific IOMMU driver during initialization,
  * to fetch ranges registered with iommu_add_extra_reserved_device_memory().
+ * This has a side effect of marking requested ranges as "reserved" in the
+ * memory map.
  */
 extern int iommu_get_extra_reserved_device_memory(iommu_grdm_t *func,
                                                   void *ctxt);
--
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