Re: [PATCH 5/5] docs/pvh: document initial MTRR state

From: Wei Liu <wei.liu2@citrix.com>
To: Roger Pau Monne <roger.pau@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <jbeulich@suse.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH 5/5] docs/pvh: document initial MTRR state
Date: Mon, 14 May 2018 17:03:52 +0100	[thread overview]
Message-ID: <20180514160352.3niqmzctpntjhoeg@citrix.com> (raw)
In-Reply-To: <20180510171505.37309-6-roger.pau@citrix.com>

On Thu, May 10, 2018 at 06:15:05PM +0100, Roger Pau Monne wrote:
> Provided to both Dom0 and DomUs.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> ---
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: George Dunlap <George.Dunlap@eu.citrix.com>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Julien Grall <julien.grall@arm.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Tim Deegan <tim@xen.org>
> Cc: Wei Liu <wei.liu2@citrix.com>
> ---
>  docs/misc/pvh.markdown | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/docs/misc/pvh.markdown b/docs/misc/pvh.markdown
> index e85fb15374..639401a887 100644
> --- a/docs/misc/pvh.markdown
> +++ b/docs/misc/pvh.markdown
> @@ -92,3 +92,18 @@ event channels. Delivery of those interrupts can be configured in the same way
>  as HVM guests, check xen/include/public/hvm/params.h and
>  xen/include/public/hvm/hvm\_op.h for more information about available delivery
>  methods.
> +
> +## MTRR ##
> +
> +### Unprivileged guests ###
> +
> +PVH guests are booted with the default MTRR type set to write-back and MTRR
> +enabled. This allows DomUs to start with a sane MTRR state. Note that this will
> +have to be revisited when pci-passthrough is added to PVH in order to set MMIO
> +regions as UC.

My reading is "revisited" implies the default type will change. In fact
it shouldn't. We should clarify: for ram it will remain WB, for MMIO
holes it will be UC.

Please correct me if I'm wrong.

Wei.

> +
> +### Hardware domain ###
> +
> +A PVH hardware domain is booted with the same MTRR state as the one found on
> +the host. This is done because the hardware domain memory map is already a
> +modified copy of the host memory map, so the same MTRR setup should work.
> -- 
> 2.17.0
> 

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