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

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Date:	Wed, 22 Jun 2016 15:41:42 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	KarimAllah Ahmed <karahmed@...zon.de>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org
Cc:	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 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?

Paolo