linux-kernel - Re: [PATCH V2 2/2] mm/migration: Add trace events for base page and HugeTLB migrations

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Message-ID: <20220125101606.3cfb5561@gandalf.local.home>
Date:   Tue, 25 Jan 2022 10:16:06 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org, naoya.horiguchi@...ux.dev,
        Ingo Molnar <mingo@...hat.com>, Zi Yan <ziy@...dia.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        John Hubbard <jhubbard@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] mm/migration: Add trace events for base page and
 HugeTLB migrations

On Tue, 25 Jan 2022 13:28:49 +0000
Matthew Wilcox <willy@...radead.org> wrote:

> On Tue, Jan 25, 2022 at 08:38:25AM +0530, Anshuman Khandual wrote:
> > +		TP_printk("addr=%lx, pte=%lx order=%d", __entry->addr, __entry->pte, __entry->order)  
> 
> In these days of increasingly advanced Rowhammer attacks, is it wise
> to let userspace know exactly which physical addresses are being
> used for virtual addresses?

Is it an issue if this is only available for privileged users?

With tracing, you can just create a kprobe to get the same information for
you as well, so this isn't giving a user anything they do not already have.

-- Steve