Re: [Xen-devel] [PATCH 0/2] x86/HVM: Properly handle SMAP check in certain cases

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Tuesday, July 8, 2014, 1:18:16 AM, you wrote:

> This patch set fixs a issue found by Sander Eikelenboom. Here is the log
> when this issue occurs:

> (d2)  Booting from Hard Disk...
> (d2)  Booting from 0000:7c00
> (XEN) irq.c:380: Dom1 callback via changed to Direct Vector 0xf3
> (XEN) irq.c:380: Dom2 callback via changed to Direct Vector 0xf3
> (XEN) Segment register inaccessible for d1v0
> (XEN) (If you see this outside of debugging activity, please report to 
> xen-devel@xxxxxxxxxxxxxxxxxxxx)

> And here is the Xen call trace:
> (XEN) [<ffff82d0801dc9c5>] vmx_get_segment_register+0x4d/0x422
> (XEN) [<ffff82d0801f4415>] guest_walk_tables_3_levels+0x189/0x520
> (XEN) [<ffff82d0802204a8>] hap_p2m_ga_to_gfn_3_levels+0x158/0x2c2
> (XEN) [<ffff82d08022062e>] hap_gva_to_gfn_3_levels+0x1c/0x1e
> (XEN) [<ffff82d0801ec215>] paging_gva_to_gfn+0xb8/0xce
> (XEN) [<ffff82d0801ba88d>] __hvm_copy+0x87/0x354
> (XEN) [<ffff82d0801bac7c>] hvm_copy_to_guest_virt_nofault+0x1e/0x20
> (XEN) [<ffff82d0801bace5>] copy_to_user_hvm+0x67/0x87
> (XEN) [<ffff82d08016237c>] update_runstate_area+0x98/0xfb
> (XEN) [<ffff82d0801623f0>] _update_runstate_area+0x11/0x39
> (XEN) [<ffff82d0801634db>] context_switch+0x10c3/0x10fa
> (XEN) [<ffff82d080126a19>] schedule+0x5a8/0x5da
> (XEN) [<ffff82d0801297f9>] __do_softirq+0x81/0x8c
> (XEN) [<ffff82d080129852>] do_softirq+0x13/0x15
> (XEN) [<ffff82d08015f70a>] idle_loop+0x67/0x77

> The root cause of this issue is that the we try to get guest's SS
> register via hvm_get_segment_register() between setting 'current'
> and reloading the VMCS context for it.

> Feng Wu (2):
>   x86/hvm: Always do SMAP check when updating runstate_guest(v)
>   x86/hvm: honor guest's option when updating secondary system time for
>     guest

>  xen/arch/x86/domain.c        | 21 ++++++++++++++++++---
>  xen/arch/x86/hvm/hvm.c       |  2 ++
>  xen/arch/x86/mm/guest_walk.c | 41 ++++++++++++++++++++++++++++-------------
>  xen/arch/x86/time.c          | 12 +++++++++++-
>  xen/include/asm-x86/domain.h | 24 ++++++++++++++++++++++--
>  xen/include/public/vcpu.h    | 10 ++++++++++
>  6 files changed, 91 insertions(+), 19 deletions(-)

Hi Feng,

Just tested it and the warning is indeed gone.

Thanks,

Sander



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