linux-kernel - Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not

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Message-ID: <85E2C33C-8873-4CC8-8D31-9A85C30F8DB5@amazon.de>
Date:   Thu, 15 Sep 2016 05:54:43 +0000
From:   "Raslan, KarimAllah" <karahmed@...zon.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Borislav Petkov <bp@...e.de>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Toshi Kani <toshi.kani@....com>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not


> On Jun 22, 2016, at 3:41 PM, Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
> 
> 
> On 22/06/2016 04:34, KarimAllah Ahmed wrote:
>> pfn_valid check is not sufficient because it only checks if a page has a struct
>> page or not, if for example "mem=" was passed to the kernel some valid pages
>> won't have a struct page. This means that if guests were assigned valid memory
>> that lies after the mem= boundary it will be passed uncached to the guest no
>> matter what the guest caching attributes are for this memory.
> 
> How can you pass memory after the mem= boundary to the guest?

Does my previous reply answer your question?

> 
> Paolo
> 

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