Re: [Xen-devel] fxsave, fnsave, ltr hang for guest OS.

[alarson@xxxxxxxx]

History: fnsave in my 32-bit protected mode OS 'hangs' when paging is
turned on.

Keir Fraser <keir.xen@xxxxxxxxx> wrote on 11/03/2010 01:48:53 AM:

> Do a 'debug=y make' build of Xen and your backtraces will be precise as 
wthe
> build will include frame pointers. Looking at these backtraces, they 
mostly
> seem to be in vmx_intr_assist() doing interrupt delivery work (e.g.,
> hvm_isa_irq_assert()). Perhaps you are stuck in some kind of interrupt
> delivery loop?

It turns out that OpenSuse provides a debug xen kernel so I was able
to use that yesterday, but I wasn't making much progress until it
occurred to me that by pressing 'd', I'm sampling the stack of xen,
but I don't know for sure which client the xen stack represents.  When
I restricted the two clients (dom0 and my os) to exclusively their own
CPU, then, if you exclude the first trace below, a pattern seems to
emerge, and it would seem that I should start with sh_page_fault().

I think I can see a path forward, but I figured I'd post hoping to get
lucky again...

(XEN) Xen call trace:
(XEN)    [<ffff82c480120ecf>] _spin_is_locked+0x0/0x20
(XEN)    [<ffff82c4801b1df4>] vpic_get_highest_priority_irq+0x52/0xc7
(XEN)    [<ffff82c4801b1eaa>] vpic_update_int_output+0x41/0x9d
(XEN)    [<ffff82c4801b27b9>] vpic_irq_negative_edge+0xab/0xc0
(XEN)    [<ffff82c4801a9bea>] hvm_isa_irq_deassert+0x8a/0xa7
(XEN)    [<ffff82c4801b2ee0>] pt_update_irq+0x1b9/0x1f2
(XEN)    [<ffff82c4801b8296>] vmx_intr_assist+0x6f/0x229

(XEN) Xen call trace:
(XEN)    [<ffff82c4801bb952>] vmx_get_segment_register+0x182/0x3a5
(XEN)    [<ffff82c4801ced63>] hvm_get_seg_reg+0x43/0x4d
(XEN)    [<ffff82c4801cf11f>] shadow_init_emulation+0xa9/0x144
(XEN)    [<ffff82c4801dfaac>] sh_page_fault__guest_2+0x18c1/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801d29bd>] sh_remove_write_access+0xcce/0xce0
(XEN)    [<ffff82c4801dfef8>] sh_page_fault__guest_2+0x1d0d/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801faacd>] __mfn_valid+0x3e/0x58
(XEN)    [<ffff82c4801d80b2>] l1e_propagate_from_guest+0xd2/0x644
(XEN)    [<ffff82c4801df0d1>] sh_page_fault__guest_2+0xee6/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801faad1>] __mfn_valid+0x42/0x58
(XEN)    [<ffff82c4801df0f7>] sh_page_fault__guest_2+0xf0c/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801faa90>] __mfn_valid+0x1/0x58
(XEN)    [<ffff82c4801de6e8>] sh_page_fault__guest_2+0x4fd/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c48017f5e0>] x86_emulate+0x2c/0xefc8
(XEN)    [<ffff82c4801dfab7>] sh_page_fault__guest_2+0x18cc/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801caae8>] set_ad_bits+0x0/0x34
(XEN)    [<ffff82c4801de6e8>] sh_page_fault__guest_2+0x4fd/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801be932>] vmx_vmexit_handler+0x3fb/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801d769a>] sh_gva_to_gfn__guest_2+0x8/0x168
(XEN)    [<ffff82c4801a20ef>] __hvm_copy+0xe7/0x3ef
(XEN)    [<ffff82c4801a4fd9>] hvm_fetch_from_guest_virt_nofault+0x46/0x48
(XEN)    [<ffff82c4801cf196>] shadow_init_emulation+0x120/0x144
(XEN)    [<ffff82c4801dfaac>] sh_page_fault__guest_2+0x18c1/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801be932>] vmx_vmexit_handler+0x3fb/0x1ab8

(XEN) Xen call trace:
(XEN)    [<ffff82c4801ced20>] hvm_get_seg_reg+0x0/0x4d
(XEN)    [<ffff82c4801dfaac>] sh_page_fault__guest_2+0x18c1/0x1d45
(XEN)    [<ffff82c4801bed2c>] vmx_vmexit_handler+0x7f5/0x1ab8


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