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Re: [Xen-devel] DomU application crashes while mmap'ing device memory on x86_64
- To: xen-devel@xxxxxxxxxxxxx
- From: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
- Date: Wed, 30 Nov 2016 21:00:51 +0200
- Delivery-date: Wed, 30 Nov 2016 19:01:17 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
I traced the problem down to vma->vm_page_prot which
in my case is set as:
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
This sets additional flags _PAGE_BIT_PSE/_PAGE_BIT_PAT +_PAGE_BIT_PCD
so after that remap_pfn_range makes Xen complain.
(pgprot_noncached(vma->vm_page_prot) == 0x80000000000000b7)
If I change prot to
vma->vm_page_prot = PAGE_SHARED;
(PAGE_SHARED == 0x8000000000000027) then I am able to mmap.
Can anyone please help me understand if this is a valid use-case for DomU
(pgprot_noncached) and if so why Xen cannot make it?
Thank you,
Oleksandr
On 11/22/2016 08:27 PM, Oleksandr Andrushchenko wrote:
Hi,
just wanted to bump this as I also have the same issue on real HW now
(x86_64)
Nov 14 10:30:18 DomU kernel: [ 1169.569936] [<ffffffff8101d60c>]
xen_mc_flush+0x19c/0x1b0
Thank you in advnce,
Oleksandr
On Mon, Nov 14, 2016 at 6:07 PM, Oleksandr Andrushchenko
<andr2000@xxxxxxxxx <mailto:andr2000@xxxxxxxxx>> wrote:
Hi, there!
Sorry for the long read ahead, but it seems I've got stuck...
I am working on a PV driver and facing an mmap issue.
This actually happens when user-space tries to mmap
the memory allocated by the driver:
cma_obj->vaddr = dma_alloc_wc(drm->dev, size, &cma_obj->paddr,
GFP_KERNEL | __GFP_NOWARN);
and maping:
vma->vm_flags &= ~VM_PFNMAP;
vma->vm_pgoff = 0;
ret = dma_mmap_wc(cma_obj->base.dev->dev, vma, cma_obj->vaddr,
cma_obj->paddr, vma->vm_end - vma->vm_start);
Return of the dma_mmap_wc is 0, but I see in the DomU kernel logs:
Nov 14 10:30:18 DomU kernel: [ 1169.569909] ------------[ cut here
]------------
Nov 14 10:30:18 DomU kernel: [ 1169.569911] WARNING: CPU: 1 PID:
5146 at /home/kernel/COD/linux/arch/x86/xen/multicalls.c:129
xen_mc_flush+0x19c/0x1b0
Nov 14 10:30:18 DomU kernel: [ 1169.569912] Modules linked in:
xen_drmfront(OE) drm_kms_helper(OE) drm(OE) fb_sys_fops
syscopyarea sysfillrect sysimgblt crct10dif_pclmul crc32_pclmul
ghash_clmulni_intel aesni_intel aes_x86_64 lrw glue_helper
ablk_helper cryptd intel_rapl_perf autofs4 [last unloaded:
xen_drmfront]
Nov 14 10:30:18 DomU kernel: [ 1169.569919] CPU: 1 PID: 5146 Comm:
lt-modetest Tainted: G W OE 4.9.0-040900rc3-generic
#201610291831
Nov 14 10:30:18 DomU kernel: [ 1169.569920] ffffc900406ffb10
ffffffff81416bf2 0000000000000000 0000000000000000
Nov 14 10:30:18 DomU kernel: [ 1169.569923] ffffc900406ffb50
ffffffff8108361b 00000081406ffb30 ffff88003f90b8e0
Nov 14 10:30:18 DomU kernel: [ 1169.569925] 0000000000000001
0000000000000010 0000000000000000 0000000000000201
Nov 14 10:30:18 DomU kernel: [ 1169.569928] Call Trace:
Nov 14 10:30:18 DomU kernel: [ 1169.569930] [<ffffffff81416bf2>]
dump_stack+0x63/0x81
Nov 14 10:30:18 DomU kernel: [ 1169.569932] [<ffffffff8108361b>]
__warn+0xcb/0xf0
Nov 14 10:30:18 DomU kernel: [ 1169.569934] [<ffffffff8108374d>]
warn_slowpath_null+0x1d/0x20
Nov 14 10:30:18 DomU kernel: [ 1169.569936] [<ffffffff8101d60c>]
xen_mc_flush+0x19c/0x1b0
Nov 14 10:30:18 DomU kernel: [ 1169.569938] [<ffffffff8101d716>]
__xen_mc_entry+0xf6/0x150
Nov 14 10:30:18 DomU kernel: [ 1169.569940] [<ffffffff81020476>]
xen_extend_mmu_update+0x56/0xd0
Nov 14 10:30:18 DomU kernel: [ 1169.569942] [<ffffffff81021d67>]
xen_set_pte_at+0x177/0x2f0
Nov 14 10:30:18 DomU kernel: [ 1169.569944] [<ffffffff811e064b>]
remap_pfn_range+0x30b/0x430
Nov 14 10:30:18 DomU kernel: [ 1169.569946] [<ffffffff815a8267>]
dma_common_mmap+0x87/0xa0
Nov 14 10:30:18 DomU kernel: [ 1169.569953] [<ffffffffc00ffa8f>]
drm_gem_cma_mmap_obj+0x8f/0xa0 [drm]
Nov 14 10:30:18 DomU kernel: [ 1169.569960] [<ffffffffc00ffac5>]
drm_gem_cma_mmap+0x25/0x30 [drm]
Nov 14 10:30:18 DomU kernel: [ 1169.569962] [<ffffffff811e79b5>]
mmap_region+0x3a5/0x640
Nov 14 10:30:18 DomU kernel: [ 1169.569964] [<ffffffff811e8096>]
do_mmap+0x446/0x530
Nov 14 10:30:18 DomU kernel: [ 1169.569966] [<ffffffff813b88b5>]
? common_mmap+0x45/0x50
Nov 14 10:30:18 DomU kernel: [ 1169.569968] [<ffffffff813b8906>]
? apparmor_mmap_file+0x16/0x20
Nov 14 10:30:18 DomU kernel: [ 1169.569970] [<ffffffff81377a5d>]
? security_mmap_file+0xdd/0xf0
Nov 14 10:30:18 DomU kernel: [ 1169.569972] [<ffffffff811c8faa>]
vm_mmap_pgoff+0xba/0xf0
Nov 14 10:30:18 DomU kernel: [ 1169.569974] [<ffffffff811e5c01>]
SyS_mmap_pgoff+0x1c1/0x290
Nov 14 10:30:18 DomU kernel: [ 1169.569976] [<ffffffff8103313b>]
SyS_mmap+0x1b/0x30
Nov 14 10:30:18 DomU kernel: [ 1169.569978] [<ffffffff8188bbbb>]
entry_SYSCALL_64_fastpath+0x1e/0xad
Nov 14 10:30:18 DomU kernel: [ 1169.569979] ---[ end trace
ce1796cb265ebe08 ]---
Nov 14 10:30:18 DomU kernel: [ 1169.569982] ------------[ cut here
]------------
And output of xl dmesg says:
(XEN) memory.c:226:d0v0 Could not allocate order=9 extent: id=31
memflags=0x40 (488 of 512)
(d31) mapping kernel into physical memory
(d31) about to get started...
(XEN) d31 attempted to change d31v0's CR4 flags 00000620 -> 00040660
(XEN) d31 attempted to change d31v1's CR4 flags 00000620 -> 00040660
(XEN) traps.c:3657: GPF (0000): ffff82d0801a1a09 -> ffff82d08024b970
(XEN) mm.c:1893:d31v0 Bad L1 flags 90
(XEN) mm.c:1893:d31v0 Bad L1 flags 90
(XEN) mm.c:1893:d31v0 Bad L1 flags 90
(XEN) mm.c:1893:d31v0 Bad L1 flags 90
My setup is a little bit tricky... I am using a Xen setup running
inside VirtualBox:
1. xl info:
host : Dom0
release : 4.4.0-45-generic
version : #66-Ubuntu SMP Wed Oct 19 14:12:37 UTC 2016
machine : x86_64
nr_cpus : 2
max_cpu_id : 1
nr_nodes : 1
cores_per_socket : 2
threads_per_core : 1
cpu_mhz : 3408
hw_caps :
178bfbff:d6d82203:28100800:00000121:00000000:00842000:00000000:00000100
virt_caps :
total_memory : 2047
free_memory : 11
sharing_freed_memory : 0
sharing_used_memory : 0
outstanding_claims : 0
free_cpus : 0
xen_major : 4
xen_minor : 8
xen_extra : .0-rc
xen_version : 4.8.0-rc
xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p
xen_scheduler : credit
xen_pagesize : 4096
platform_params : virt_start=0xffff800000000000
xen_changeset :
xen_commandline : placeholder
cc_compiler : gcc (Debian 6.2.0-10) 6.2.0 20161027
cc_compile_by : ijackson
cc_compile_domain : chiark.greenend.org.uk
<http://chiark.greenend.org.uk>
cc_compile_date : Tue Nov 1 18:11:16 UTC 2016
build_id : 3744fa5e7a5b01a0439ba4413e41a7a1c505d5ee
xend_config_format : 4
2. DomU
Linux DomU 4.9.0-040900rc3-generic #201610291831 SMP Sat Oct 29
22:32:46 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
Could anyone please give me any hint on what needs to
be checked and how this can be resolved?
Thank you,
Oleksandr Andrushchenko
--
Best regards,
Oleksandr Andrushchenko
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