Message-ID: <530786A2.6080406@hp.com>
Date: Fri, 21 Feb 2014 12:02:26 -0500
From: Waiman Long <waiman.long@hp.com>
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To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michel Lespinasse <walken@google.com>,
        Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        George Spelvin <linux@horizon.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Daniel J Blueman <daniel@numascale.com>,
        Alexander Fyodorov <halcy@yandex.ru>,
        Aswin Chandramouleeswaran <aswin@hp.com>,
        Scott J Norton <scott.norton@hp.com>,
        Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@hp.com>
Subject: Re: [PATCH v4 0/3] qspinlock: Introducing a 4-byte queue spinlock
References: <1392669684-4807-1-git-send-email-Waiman.Long@hp.com> <53029167.4060109@zytor.com> <20140218073111.GW27965@twins.programming.kicks-ass.net> <5303B4C4.2040907@hp.com> <20140218212827.GR14089@laptop.programming.kicks-ass.net> <5303FDEC.9060001@hp.com> <20140219085107.GG27965@twins.programming.kicks-ass.net> <53050501.3070101@hp.com> <CA+55aFwyVgLJq2OgKZBK7g+T5-_M4o+dnEAr+qtYxA5t_=HSvA@mail.gmail.com> <5306413F.3010106@hp.com> <53065838.90102@linux.vnet.ibm.com>
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On 02/20/2014 02:32 PM, Raghavendra K T wrote:
> On 02/20/2014 11:24 PM, Waiman Long wrote:
>
>> Now the key is how to detect if a kernel is really running in a PV
>> environment. I need to ask some virtualization experts on that.
>>
>
> For kvm you could just follow,
> kvm_spinlock_init_jump() and KVM_FEATURE_* encoding in cpuid
> part __do_cpuid_ent().
>

I saw that in the arch/x86/kernel/kvm.c file. So I think I can use the 
returned value of kvm_para_available() to decide if it is running in a 
KVM guest. However, I am not so sure of what to use in xen.

-Longman
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