From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Vrabel <david.vrabel@citrix.com>
Subject: Re: [Xen-devel] [PATCH v5 1/2] xen: add xen_is_preemptible_hypercall()
Date: Tue, 3 Feb 2015 11:05:15 +0000
Message-ID: <54D0AB6B.9060909@citrix.com>
References: <1422323467-16713-1-git-send-email-mcgrof@do-not-panic.com> <1422323467-16713-2-git-send-email-mcgrof@do-not-panic.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 8bit
Cc: Borislav Petkov <bp@suse.de>, <kvm@vger.kernel.org>,
	"Luis R. Rodriguez" <mcgrof@suse.com>, <x86@kernel.org>,
	<linux-kernel@vger.kernel.org>, <rostedt@goodmis.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Ingo Molnar <mingo@redhat.com>,
	Jan Beulich <JBeulich@suse.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	<paulmck@linux.vnet.ibm.com>
To: "Luis R. Rodriguez" <mcgrof@do-not-panic.com>,
	<david.vrabel@citrix.com>, <konrad.wilk@oracle.com>,
	<boris.ostrovsky@oracle.com>, <xen-devel@lists.xenproject.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1422323467-16713-2-git-send-email-mcgrof@do-not-panic.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On 27/01/15 01:51, Luis R. Rodriguez wrote:
> 
> +#ifndef CONFIG_PREEMPT
> +extern struct { char _entry[32]; } preemptible_hypercall_page[];
> +
> +static inline bool xen_is_preemptible_hypercall(struct pt_regs *regs)
> +{
> +	return !user_mode_vm(regs) &&
> +		regs->ip >= (unsigned long)preemptible_hypercall_page &&
> +		regs->ip < (unsigned long)preemptible_hypercall_page + PAGE_SIZE;

I asked for this test to be optimized.

	return (regs->ip >> PAGE_SHIFT)
            == ((unsigned long)preemptible_hypercall_page >> PAGE_SHIFT)
	    && !user_mode_vm(regs);

David