linux-kernel - Re: [PATCH] x86, kvm: Handle PFNs outside of kernel reach when touching GPTEs

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Date:   Tue, 18 Apr 2017 10:12:34 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiao Guangrong <guangrong.xiao@...il.com>,
        "Sironi, Filippo" <sironi@...zon.de>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     "Liguori, Anthony" <aliguori@...zon.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, kvm: Handle PFNs outside of kernel reach when
 touching GPTEs



On 17/04/2017 13:26, Xiao Guangrong wrote:
>>
> 
> Sounds reasonable, however it is incomplete so far as there are some
> code paths still do not support non-page backend memory, e.g,
> emulator_cmpxchg_emulated().
> 
> I would suggest to unify the code introduced in this patch with existing
> hva_to_pfn(), also we can introduce a common API, maybe named
> kvm_map_hva(), to improve the caller sides.

I agree with Guangrong's suggestion.

Paolo

> BTW, i do not know why we used kmap_atomic() rather than kmap(), the
> path of cmpxchg_gpte() is sleep-able anyway.