Re: [PATCH] xen/p2m: fix extra memory regions accounting

[Juergen Gross]

On 09/03/2015 02:15 PM, Roger Pau Monnà wrote:
> El 03/09/15 a les 14.05, Roger Pau Monne ha escrit:
> > On systems with memory maps with ranges that don't end at page boundaries,
> > like:
> >
> > [...]
> > (XEN)  0000000000100000 - 00000000dfdf9c00 (usable)
> > (XEN)  00000000dfdf9c00 - 00000000dfe4bc00 (ACPI NVS)
> > [...]
> >
> > xen_add_extra_mem will create a protected range that ends up at 0xdfdf9c00,
> > but the function used to check if a memory address is inside of a protected
> > range works with pfns, which means that an attempt to map 0xdfdf9c00 will be
> > refused because the check is performed against 0xdfdf9000 instead of
> > 0xdfdf9c00.
> >
> > In order to fix this, make sure that the ranges that are added to the
> > xen_extra_mem array are aligned to page boundaries.
> >
> > Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> > Cc: Juergen Gross <jgross@xxxxxxxx>
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> > ---
> > AFAICT this patch needs to be backported to 3.19, 4.0, 4.1 and 4.2.
> > ---
> >   arch/x86/xen/setup.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> > index 55f388e..dcf5865 100644
> > --- a/arch/x86/xen/setup.c
> > +++ b/arch/x86/xen/setup.c
> > @@ -68,6 +68,9 @@ static void __init xen_add_extra_mem(phys_addr_t start, phys_addr_t size)
> >   {
> >   	int i;
> >
> > +	start = PAGE_ALIGN(start);
>
> Sorry, I didn't remember to update the patch before sending it, but I
> think this should instead be:
>
> start = round_up(start, PAGE_SIZE);

No, PAGE_ALIGN() already does that.


Juergen

> Here and below.
>
> > +	size &= PAGE_MASK;
> > +
> >   	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
> >   		/* Add new region. */
> >   		if (xen_extra_mem[i].size == 0) {
> > @@ -92,6 +95,9 @@ static void __init xen_del_extra_mem(phys_addr_t start, phys_addr_t size)
> >   	int i;
> >   	phys_addr_t start_r, size_r;
> >
> > +	start = PAGE_ALIGN(start);
> > +	size &= PAGE_MASK;
> > +
> >   	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
> >   		start_r = xen_extra_mem[i].start;
> >   		size_r = xen_extra_mem[i].size;
>
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