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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

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

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

[Xen-devel] DomU application crashes while mmap'ing device memory on x86_64