linux-kernel - Re: [PATCH v8 4/5] x86/mm: Add noalias variants of set_memory

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Date:   Tue, 28 Jun 2022 13:15:21 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 4/5] x86/mm: Add noalias variants of
 set_memory_*crypted() functions


> 
> I still don't like the idea of using the DMA API itself.  But, maybe we
> need some common infrastructure that the DMA API and this code use which
> says, "get me some pages that I can safely make shared".

Right.  For instance any KVM PV feature would require shared memory, and DMA API
normally doesn't fit (taking 'struct kvm_steal_time' as example).

Maybe we can reserve a CMA for this purpose.

-- 
Thanks,
-Kai