Re: [Xen-devel] [RFC PATCH 1/3] x86/setup: Don't skip 2MiB underneath relocated Xen image

From: "Durrant, Paul" <pdurrant@amazon.co.uk>
To: David Woodhouse <dwmw2@infradead.org>,
	Xen-devel <xen-devel@lists.xenproject.org>
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
	"Julien Grall" <julien@xen.org>, "Wei Liu" <wl@xen.org>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
	"George Dunlap" <George.Dunlap@eu.citrix.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"paul@xen.org" <paul@xen.org>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"Jan Beulich" <jbeulich@suse.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [RFC PATCH 1/3] x86/setup: Don't skip 2MiB underneath relocated Xen image
Date: Fri, 10 Jan 2020 11:15:13 +0000	[thread overview]
Message-ID: <b682f2100c234e9a930e4001d33bcf8e@EX13D32EUC003.ant.amazon.com> (raw)
In-Reply-To: <20200108172500.1419665-1-dwmw2@infradead.org>

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of
> David Woodhouse
> Sent: 08 January 2020 17:25
> To: Xen-devel <xen-devel@lists.xenproject.org>
> Cc: Stefano Stabellini <sstabellini@kernel.org>; Julien Grall
> <julien@xen.org>; Wei Liu <wl@xen.org>; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>; George Dunlap <George.Dunlap@eu.citrix.com>;
> Andrew Cooper <andrew.cooper3@citrix.com>; paul@xen.org; Ian Jackson
> <ian.jackson@eu.citrix.com>; Jan Beulich <jbeulich@suse.com>; Roger Pau
> Monné <roger.pau@citrix.com>
> Subject: [Xen-devel] [RFC PATCH 1/3] x86/setup: Don't skip 2MiB underneath
> relocated Xen image
> 
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> Set 'e' correctly to reflect the location that Xen is actually relocated
> to from its default 2MiB location. Not 2MiB below that.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>  xen/arch/x86/setup.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 501f3f5e4b..47e065e5fe 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1077,9 +1077,9 @@ void __init noreturn __start_xen(unsigned long
> mbi_p)
>              unsigned long pte_update_limit;
> 
>              /* Select relocation address. */
> -            e = end - reloc_size;
> -            xen_phys_start = e;
> -            bootsym(trampoline_xen_phys_start) = e;
> +            xen_phys_start = end - reloc_size;
> +            e = xen_phys_start + XEN_IMG_OFFSET;
> +            bootsym(trampoline_xen_phys_start) = xen_phys_start;
> 
>              /*
>               * No PTEs pointing above this address are candidates for
> relocation.

Do you not also need to adjust the setting of pte_update_limit that's just out of context below here?

  Paul
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