Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 20 Mar 2020 14:47:41 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH] x86/mm: Make pud_present() check _PAGE_PROTNONE and
 _PAGE_PSE as well
Message-ID: <20200320114741.c62iolt2yzltnscf@box>
References: <1584507679-11976-1-git-send-email-anshuman.khandual@arm.com>
 <c03165c8-6d44-49c2-2dad-a85759200718@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <c03165c8-6d44-49c2-2dad-a85759200718@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Mar 20, 2020 at 08:53:16AM +0530, Anshuman Khandual wrote:
> 
> 
> On 03/18/2020 10:31 AM, Anshuman Khandual wrote:
> > pud_present() should also check _PAGE_PROTNONE and _PAGE_PSE bits like in
> > case pmd_present(). This makes a PUD entry test positive for pud_present()
> > after getting invalidated with pud_mknotpresent(), hence standardizing the
> > semantics with PMD helpers.
> > 
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Dave Hansen <dave.hansen@intel.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: x86@kernel.org
> > Cc: linux-mm@kvack.org
> > Cc: linux-kernel@vger.kernel.org
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> > ---
> > Even though pud_mknotpresent() is not used any where currently, there is
> > a discrepancy between PMD and PUD.
> > 
> > WARN_ON(!pud_present(pud_mknotpresent(pud_mkhuge(pud)))) -> Fail
> > WARN_ON(!pmd_present(pmd_mknotpresent(pmd_mkhuge(pmd)))) -> Pass
> > 
> > Though pud_mknotpresent() currently clears _PAGE_PROTNONE, pud_present()
> > does not check it. This change fixes both inconsistencies.
> > 
> > This has been build and boot tested on x86.
> 
> Adding Kirill and Dan.
> 
> +Cc: Kirill A. Shutemov <kirill@shutemov.name>
> +Cc: Dan Williams <dan.j.williams@intel.com>

Or we can just drop the pud_mknotpresent(). There's no users AFAICS and
only x86 provides it.

-- 
 Kirill A. Shutemov