linux-kernel - Re: [PATCH 1/2] Xen: Delay remapping memory of pv-domain

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Message-ID: <544FD3A2.1050903@citrix.com>
Date:	Tue, 28 Oct 2014 17:34:26 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<boris.ostrovsky@...cle.com>
Subject: Re: [PATCH 1/2] Xen: Delay remapping memory of pv-domain

Can these patches be split up?  They're hard to review as-is.  e.g., the
changes to page allocation look they could be split out.

On 27/10/14 14:52, Juergen Gross wrote:
> Early in the boot process the memory layout of a pv-domain is changed
> to match the E820 map (either the host one for Dom0 or the Xen one)
> regarding placement of RAM and PCI holes. This requires removing memory
> pages initially located at positions not suitable for RAM and adding
> them later at higher addresses where no restrictions apply.

How does this impact Matt Rushton's recent change to ensure the
relocated frames are contiguous?

The change was "xen/setup: Remap Xen Identity Mapped RAM" (4fbb67e3c87).

> +	/* Update kernel mapping */
> +	if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
> +					 mfn_pte(mfn, PAGE_KERNEL), 0)) {
> +		WARN(1, "Failed to update kernel mapping for mfn=%ld pfn=%ld\n",
> +		      mfn, pfn);
> +		return 0;

I think you need to check if this is a PFN for a high page before
updating the mapping.

David
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