Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests

From	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests
Date	2015-12-15 16:30 +0100
Message-ID	<qFZI5-5X4-1@gated-at.bofh.it> (permalink)
References	<qwFpf-6AK-5@gated-at.bofh.it> <qwFpf-6AK-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 11/19/2015 04:55 PM, Boris Ostrovsky wrote:
> After 32-bit syscall rewrite, and specifically after commit 5f310f739b4c
> ("x86/entry/32: Re-implement SYSENTER using the new C path"), the stack
> frame that is passed to xen_sysexit is no longer a "standard" one (i.e.
> it's not pt_regs).
>
> Since we end up calling xen_iret from xen_sysexit we don't need to fix
> up the stack and instead follow entry_SYSENTER_32's IRET path directly
> to xen_iret.
>
> We can do the same thing for compat mode even though stack does not need
> to be fixed. This will allow us to drop usergs_sysret32 paravirt op (in
> the subsequent patch)
>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Suggested-by: Andy Lutomirski <luto@amacapital.net>


I know this has been in the tip tree --- when do you think this will go 
Linus tree? In the 4.4 timeframe?

Xen 32-bit PV guests are broken without this.


Thanks.
-boris

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Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-15 16:30 +0100
  Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Borislav Petkov <bp@suse.de> - 2015-12-15 16:50 +0100
    Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Andy Lutomirski <luto@amacapital.net> - 2015-12-15 17:00 +0100
    Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-15 17:10 +0100

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