linux-kernel - Re: [PATCH v29 09/32] x86/mm: Introduce _PAGE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b545f4957412884d8e0fed88235a8d23fc6060c1.camel@intel.com>
Date:   Sun, 22 Aug 2021 02:59:54 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "Xu, Pengfei" <pengfei.xu@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "esyr@...hat.com" <esyr@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "Yu, Yu-cheng" <yu-cheng.yu@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "bsingharora@...il.com" <bsingharora@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        "nadav.amit@...il.com" <nadav.amit@...il.com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>, "oleg@...hat.com" <oleg@...hat.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "pavel@....cz" <pavel@....cz>, "arnd@...db.de" <arnd@...db.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "Dave.Martin@....com" <Dave.Martin@....com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "gorcunov@...il.com" <gorcunov@...il.com>
CC:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v29 09/32] x86/mm: Introduce _PAGE_COW

On Sat, 2021-08-21 at 19:20 +0000, Edgecombe, Rick P wrote:
> +KVM list.
> 
> On Fri, 2021-08-20 at 11:11 -0700, Yu-cheng Yu wrote:
> >  
> >  static inline int pte_write(pte_t pte)
> >  {
> > -       return pte_flags(pte) & _PAGE_RW;
> > +       /*
> > +        * Shadow stack pages are always writable - but not by
> > normal
> > +        * instructions, and only by shadow stack operations. 
> > Therefore,
> > +        * the W=0,D=1 test with pte_shstk().
> > +        */
> > +       return (pte_flags(pte) & _PAGE_RW) || pte_shstk(pte);
> >  }
> >  
> 
> KVM uses this in a couple places when checking EPT ptes. But bit 6
> (dirty) is a totally different meaning in EPT. I think it's just used
> to trigger an optimization, but wondering if KVM should have its own
> TDP specific function instead of using pte_write().
> 
Argh, never mind. I misread the new KVM mmu notifier refactor.