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Subject: Re: [patch V5 09/38] x86/entry: Switch XEN/PV hypercall entry to
 IDTENTRY
To:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     x86@kernel.org, "Paul E. McKenney" <paulmck@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Alexandre Chartre <alexandre.chartre@oracle.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        Juergen Gross <jgross@suse.com>,
        Brian Gerst <brgerst@gmail.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Will Deacon <will@kernel.org>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Wei Liu <wei.liu@kernel.org>,
        Michael Kelley <mikelley@microsoft.com>,
        Jason Chen CJ <jason.cj.chen@intel.com>,
        Zhao Yakui <yakui.zhao@intel.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>
References: <20200512210059.056244513@linutronix.de>
 <20200512213810.320365524@linutronix.de>
From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Message-ID: <2c4b693f-afd8-302b-99c7-d1f0444cd767@oracle.com>
Date:   Thu, 14 May 2020 12:24:37 -0400
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On 5/12/20 5:01 PM, Thomas Gleixner wrote:
> Convert the XEN/PV hypercall to IDTENTRY:
>
>   - Emit the ASM stub with DECLARE_IDTENTRY
>   - Remove the ASM idtentry in 64bit
>   - Remove the open coded ASM entry code in 32bit
>   - Remove the old prototypes
>
> The handler stubs need to stay in ASM code as it needs corner case hand=
ling
> and adjustment of the stack pointer.
>
> Provide a new C function which invokes the entry/exit handling and call=
s
> into the XEN handler on the interrupt stack.
>
> The exit code is slightly different from the regular idtentry_exit() on=

> non-preemptible kernels. If the hypercall is preemptible and need_resch=
ed()
> is set then XEN provides a preempt hypercall scheduling function. Add i=
t as
> conditional path to __idtentry_exit() so the function can be reused.
>
> __idtentry_exit() is forced inlined so on the regular idtentry_exit() p=
ath
> the extra condition is optimized out by the compiler.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Juergen Gross <jgross@suse.com>
> ---
> V5: Move DECLARE_PER_CPU(bool, xen_in_preemptible_hcall) out of ifdeffe=
ry
>     to avoid #ifdeffery in idtentry_exit().
>     Convert to the reworked stack switching helper
>     Fixed up the XEN callback initialization (Boris O.)
> ---
>  arch/x86/entry/common.c         |   57 +++++++++++++++++++++++++++++++=
+++++++--
>  arch/x86/entry/entry_32.S       |   17 ++++++-----
>  arch/x86/entry/entry_64.S       |   22 ++++-----------
>  arch/x86/include/asm/idtentry.h |   13 +++++++++
>  arch/x86/xen/setup.c            |    4 ++
>  arch/x86/xen/smp_pv.c           |    3 +-
>  arch/x86/xen/xen-asm_32.S       |   12 ++++----
>  arch/x86/xen/xen-asm_64.S       |    2 -
>  arch/x86/xen/xen-ops.h          |    1=20
>  drivers/xen/preempt.c           |    2 -
>  include/xen/xen-ops.h           |    7 +++-
>  11 files changed, 103 insertions(+), 37 deletions(-)


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>