[tip:x86/mm] x86/mm/64: Enable SWIOTLB if system has SRAT memory regions above MAX_DMA32_PFN

[tip-bot for Igor Mammedov]

Commit-ID:  ec941c5ffede4d788b9fc008f9eeca75b9e964f5
Gitweb:     http://git.kernel.org/tip/ec941c5ffede4d788b9fc008f9eeca75b9e964f5
Author:     Igor Mammedov <imammedo@xxxxxxxxxx>
AuthorDate: Fri, 4 Dec 2015 14:07:06 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sun, 6 Dec 2015 12:46:31 +0100

x86/mm/64: Enable SWIOTLB if system has SRAT memory regions above MAX_DMA32_PFN

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.

Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: akataria@xxxxxxxxxx
Cc: fujita.tomonori@xxxxxxxxxxxxx
Cc: konrad.wilk@xxxxxxxxxx
Cc: pbonzini@xxxxxxxxxx
Cc: revers@xxxxxxxxxx
Cc: riel@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1449234426-273049-3-git-send-email-imammedo@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/pci-swiotlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index adf0392..7c577a1 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -88,7 +88,7 @@ int __init pci_swiotlb_detect_4gb(void)
 {
 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
 #ifdef CONFIG_X86_64
-	if (!no_iommu && max_pfn > MAX_DMA32_PFN)
+	if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
 		swiotlb = 1;
 #endif
 	return swiotlb;
--
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