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[PATCH v2 0/2] x86: enable SWIOTLB if system has SRAT memory regions above MAX_DMA32_PFN

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  [PATCH v2 0/2] x86: enable SWIOTLB if system has SRAT memory regions above MAX_DMA32_PFN Igor Mammedov <imammedo@redhat.com> - 2015-12-04 12:30 +0100
    [PATCH v2 1/2] x86: introduce max_possible_pfn Igor Mammedov <imammedo@redhat.com> - 2015-12-04 12:30 +0100

#1283718 — [PATCH v2 0/2] x86: enable SWIOTLB if system has SRAT memory regions above MAX_DMA32_PFN

changes since v1:
  - reduce # of #ifdefs by introducing max_possible_pfn
    global variable
  - don't check 'acpi_no_memhotplug=1' for disabling
    SWIOTLB initialization, since existing 'no_iommu'
    kernel option could be used to the same effect.
  - split into 2 patches
      - 1st adds max_possible_pfn,
      - 2nd fixes bug enabling SWIOTLB when it's needed

when memory hotplug enabled system is booted with less
than 4GB of RAM and then later more RAM is hotplugged
32-bit devices stop functioning with following error:

 nommu_map_single: overflow 327b4f8c0+1522 of device mask ffffffff

the reason for this is that if x86_64 system were booted
with RAM less than 4GB, it doesn't enable SWIOTLB and
when memory is hotplugged beyond MAX_DMA32_PFN, devices
that expect 32-bit addresses can't handle 64-bit addresses.

Fix it by tracking max possible PFN when parsing
memory affinity structures from SRAT ACPI table and
enable SWIOTLB if there is hotpluggable memory
regions beyond MAX_DMA32_PFN.

It fixes KVM guests when they use emulated devices
(reproduces with ata_piix, e1000 and usb devices,
 RHBZ: 1275941, 1275977, 1271527)
It also fixes the HyperV, VMWare with emulated devices
which are affected by this issue as well.

ref to v1:
  https://lkml.org/lkml/2015/11/30/594

Igor Mammedov (2):
  x86: introduce max_possible_pfn
  x86_64: enable SWIOTLB if system has SRAT memory regions above
    MAX_DMA32_PFN

 arch/x86/kernel/pci-swiotlb.c | 2 +-
 arch/x86/kernel/setup.c       | 2 ++
 arch/x86/mm/srat.c            | 3 +++
 include/linux/bootmem.h       | 4 ++++
 mm/bootmem.c                  | 1 +
 mm/nobootmem.c                | 1 +
 6 files changed, 12 insertions(+), 1 deletion(-)

-- 
1.8.3.1

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#1283719 — [PATCH v2 1/2] x86: introduce max_possible_pfn

max_possible_pfn will be used for tracking max possible
PFN for memory that isn't present in E820 table and
could be hotplugged later.

By default max_possible_pfn is initialized with max_pfn,
but a follow up patch will update it with highest PFN of
hotpluggable memory ranges declared in ACPI SRAT table
if any present.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 arch/x86/kernel/setup.c | 2 ++
 include/linux/bootmem.h | 4 ++++
 mm/bootmem.c            | 1 +
 mm/nobootmem.c          | 1 +
 4 files changed, 8 insertions(+)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 29db25f..16a8465 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1048,6 +1048,8 @@ void __init setup_arch(char **cmdline_p)
 	if (mtrr_trim_uncached_memory(max_pfn))
 		max_pfn = e820_end_of_ram_pfn();
 
+	max_possible_pfn = max_pfn;
+
 #ifdef CONFIG_X86_32
 	/* max_low_pfn get updated here */
 	find_low_pfn_range();
diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index f589222..5b39aa5 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -19,6 +19,10 @@ extern unsigned long min_low_pfn;
  * highest page
  */
 extern unsigned long max_pfn;
+/*
+ * highest possible page
+ */
+extern unsigned long max_possible_pfn;
 
 #ifndef CONFIG_NO_BOOTMEM
 /*
diff --git a/mm/bootmem.c b/mm/bootmem.c
index 3b63807..221a04b 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -33,6 +33,7 @@ EXPORT_SYMBOL(contig_page_data);
 unsigned long max_low_pfn;
 unsigned long min_low_pfn;
 unsigned long max_pfn;
+unsigned long max_possible_pfn;
 
 bootmem_data_t bootmem_node_data[MAX_NUMNODES] __initdata;
 
diff --git a/mm/nobootmem.c b/mm/nobootmem.c
index e57cf24..08614c8 100644
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -31,6 +31,7 @@ EXPORT_SYMBOL(contig_page_data);
 unsigned long max_low_pfn;
 unsigned long min_low_pfn;
 unsigned long max_pfn;
+unsigned long max_possible_pfn;
 
 static void * __init __alloc_memory_core_early(int nid, u64 size, u64 align,
 					u64 goal, u64 limit)
-- 
1.8.3.1

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