Date:	Fri, 26 Dec 2014 14:13:51 +0900
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	<zhen-hual@...com>
CC:	<dwmw2@...radead.org>, <bhe@...hat.com>, <joro@...tes.org>,
	<vgoyal@...hat.com>, <dyoung@...hat.com>,
	<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, <kexec@...ts.infradead.org>,
	<alex.williamson@...hat.com>, <ddutile@...hat.com>,
	<ishii.hironobu@...fujitsu.com>, <bhelgaas@...gle.com>,
	<doug.hatch@...com>, <jerry.hoemann@...com>, <tom.vaden@...com>,
	<li.zhang6@...com>, <lisa.mitchell@...com>,
	<billsumnerlinux@...il.com>
Subject: Re: [PATCH 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

Hi Zhen-Hua,

I tested your patch and found two problems.

[1]
Kenel panic occurs during 2nd kernel boot.

..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
Kernel panic - not syncing: timer doesn't work through Interrupt-remapped IO-APIC
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.18.0 #25
Hardware name: FUJITSU-SV PRIMERGY BX920 S2/D3030, BIOS 080015 Rev.3D81.3030 02/10/2012
 0000000000000002 ffff880036167d08 ffffffff815b1c6a 0000000000000000
 ffffffff817f7670 ffff880036167d88 ffffffff815b19f1 0000000000000008
 ffff880036167d98 ffff880036167d38 ffffffff810a5d2f ffff880036167d98
Call Trace:
 [<ffffffff815b1c6a>] dump_stack+0x48/0x5e
 [<ffffffff815b19f1>] panic+0xbb/0x1fa
 [<ffffffff810a5d2f>] ? vprintk_default+0x1f/0x30
 [<ffffffff814c6a6c>] panic_if_irq_remap+0x1c/0x20
 [<ffffffff81b53985>] check_timer+0x1e7/0x5ed
 [<ffffffff8129bd9d>] ? radix_tree_lookup+0xd/0x10
 [<ffffffff81b5413b>] setup_IO_APIC+0x261/0x292
 [<ffffffff81b50302>] native_smp_prepare_cpus+0x214/0x25d
 [<ffffffff81b41c65>] kernel_init_freeable+0x1dc/0x28c
 [<ffffffff815aaf00>] ? rest_init+0x80/0x80
 [<ffffffff815aaf0e>] kernel_init+0xe/0xf0
 [<ffffffff815b5d2c>] ret_from_fork+0x7c/0xb0
 [<ffffffff815aaf00>] ? rest_init+0x80/0x80
---[ end Kernel panic - not syncing: timer doesn't work through Interrupt-remapped IO-APIC


This panic seems to be related to unflushed cache. I confirmed this
problem was fixed by the following patch.

--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -200,8 +200,13 @@ static int modify_irte(int irq, struct irte *irte_modified)
 	set_64bit(&irte->high, irte_modified->high);
 
 #ifdef CONFIG_CRASH_DUMP
-	if (is_kdump_kernel())
+	if (is_kdump_kernel()) {
 		__iommu_update_old_irte(iommu, index);
+		__iommu_flush_cache(iommu,
+			iommu->ir_table->base_old_virt +
+			index * sizeof(struct irte),
+			sizeof(struct irte));
+	}
 #endif
 	__iommu_flush_cache(iommu, irte, sizeof(*irte));
 

[2]
Some DMAR error messages are still found in 2nd kernel boot.

dmar: DRHD: handling fault status reg 2
dmar: DMAR:[DMA Write] Request device [01:00.0] fault addr ffded000
DMAR:[fault reason 01] Present bit in root entry is clear

I confiremd your commit 1a2262 was already applied. Any idea?

Thanks,
Takao Indoh


On 2014/12/22 18:15, Li, Zhen-Hua wrote:
> This patchset is an update of Bill Sumner's patchset, implements a fix for:
> If a kernel boots with intel_iommu=on on a system that supports intel vt-d,
> when a panic happens, the kdump kernel will boot with these faults:
> 
>      dmar: DRHD: handling fault status reg 102
>      dmar: DMAR:[DMA Read] Request device [01:00.0] fault addr fff80000
>      DMAR:[fault reason 01] Present bit in root entry is clear
> 
>      dmar: DRHD: handling fault status reg 2
>      dmar: INTR-REMAP: Request device [[61:00.0] fault index 42
>      INTR-REMAP:[fault reason 34] Present field in the IRTE entry is clear
> 
> On some system, the interrupt remapping fault will also happen even if the
> intel_iommu is not set to on, because the interrupt remapping will be enabled
> when x2apic is needed by the system.
> 
> The cause of the DMA fault is described in Bill's original version, and the
> INTR-Remap fault is caused by a similar reason. In short, the initialization
> of vt-d drivers causes the in-flight DMA and interrupt requests get wrong
> response.
> 
> To fix this problem, we modifies the behaviors of the intel vt-d in the
> crashdump kernel:
> 
> For DMA Remapping:
> 1. To accept the vt-d hardware in an active state,
> 2. Do not disable and re-enable the translation, keep it enabled.
> 3. Use the old root entry table, do not rewrite the RTA register.
> 4. Malloc and use new context entry table and page table, copy data from the
>     old ones that used by the old kernel.
> 5. to use different portions of the iova address ranges for the device drivers
>     in the crashdump kernel than the iova ranges that were in-use at the time
>     of the panic.
> 6. After device driver is loaded, when it issues the first dma_map command,
>     free the dmar_domain structure for this device, and generate a new one, so
>     that the device can be assigned a new and empty page table.
> 7. When a new context entry table is generated, we also save its address to
>     the old root entry table.
> 
> For Interrupt Remapping:
> 1. To accept the vt-d hardware in an active state,
> 2. Do not disable and re-enable the interrupt remapping, keep it enabled.
> 3. Use the old interrupt remapping table, do not rewrite the IRTA register.
> 4. When ioapic entry is setup, the interrupt remapping table is changed, and
>     the updated data will be stored to the old interrupt remapping table.
> 
> Advantages of this approach:
> 1. All manipulation of the IO-device is done by the Linux device-driver
>     for that device.
> 2. This approach behaves in a manner very similar to operation without an
>     active iommu.
> 3. Any activity between the IO-device and its RMRR areas is handled by the
>     device-driver in the same manner as during a non-kdump boot.
> 4. If an IO-device has no driver in the kdump kernel, it is simply left alone.
>     This supports the practice of creating a special kdump kernel without
>     drivers for any devices that are not required for taking a crashdump.
> 5. Minimal code-changes among the existing mainline intel vt-d code.
> 
> Summary of changes in this patch set:
> 1. Added some useful function for root entry table in code intel-iommu.c
> 2. Added new members to struct root_entry and struct irte;
> 3. Functions to load old root entry table to iommu->root_entry from the memory
>     of old kernel.
> 4. Functions to malloc new context entry table and page table and copy the data
>     from the old ones to the malloced new ones.
> 5. Functions to enable support for DMA remapping in kdump kernel.
> 6. Functions to load old irte data from the old kernel to the kdump kernel.
> 7. Some code changes that support other behaviours that have been listed.
> 8. In the new functions, use physical address as "unsigned long" type, not
>     pointers.
> 
> Original version by Bill Sumner:
>      https://lkml.org/lkml/2014/1/10/518
>      https://lkml.org/lkml/2014/4/15/716
>      https://lkml.org/lkml/2014/4/24/836
> 
> Zhenhua's last of Bill's patchset:
>      https://lkml.org/lkml/2014/10/21/134
>      https://lkml.org/lkml/2014/12/15/121
> 
> Changed in this version:
> 1. Do not disable and re-enable traslation and interrupt remapping.
> 2. Use old root entry table.
> 3. Use old interrupt remapping table.
> 4. Use "unsigned long" as physical address.
> 5. Use intel_unmap to unmap the old dma;
> 
> This patchset should be applied with this one together:
>      https://lkml.org/lkml/2014/11/5/43
>      x86/iommu: fix incorrect bit operations in setting values
> 
> Bill Sumner (5):
>    iommu/vt-d: Update iommu_attach_domain() and its callers
>    iommu/vt-d: Items required for kdump
>    iommu/vt-d: data types and functions used for kdump
>    iommu/vt-d: Add domain-id functions
>    iommu/vt-d: enable kdump support in iommu module
> 
> Li, Zhen-Hua (10):
>    iommu/vt-d: Update iommu_attach_domain() and its callers
>    iommu/vt-d: Items required for kdump
>    iommu/vt-d: Add domain-id functions
>    iommu/vt-d: functions to copy data from old mem
>    iommu/vt-d: Add functions to load and save old re
>    iommu/vt-d: datatypes and functions used for kdump
>    iommu/vt-d: enable kdump support in iommu module
>    iommu/vtd: assign new page table for dma_map
>    iommu/vt-d: Copy functions for irte
>    iommu/vt-d: Use old irte in kdump kernel
> 
>   drivers/iommu/intel-iommu.c         | 1050 +++++++++++++++++++++++++++++++++--
>   drivers/iommu/intel_irq_remapping.c |   99 +++-
>   include/linux/intel-iommu.h         |   18 +
>   3 files changed, 1123 insertions(+), 44 deletions(-)
> 


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