Messages in this thread | | | Subject | Re: [PATCH] xen/p2m: fix extra memory regions accounting | From | Juergen Gross <> | Date | Thu, 3 Sep 2015 16:50:54 +0200 |
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On 09/03/2015 04:38 PM, Roger Pau Monné wrote: > El 03/09/15 a les 14.25, Juergen Gross ha escrit: >> On 09/03/2015 02:05 PM, Roger Pau Monne wrote: >>> 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 Monné <roger.pau@citrix.com> >>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> >>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> >>> Cc: David Vrabel <david.vrabel@citrix.com> >>> Cc: Juergen Gross <jgross@suse.com> >>> Cc: xen-devel@lists.xenproject.org >>> --- >>> 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); >>> + size &= PAGE_MASK; >> >> This is not correct. If start wasn't page aligned and size was, you'll >> add one additional page to xen_extra_mem. > > I'm not understanding this, let's put an example: > > start = 0x8c00 > size = 0x1000 > > After the fixup added above this would become: > > start = 0x9000 > size = 0x1000 > > So if anything, I'm adding one page less (because 0x8000 was partly > added, and with the fixup it is not added).
You'd add 9c00-9cff which shouldn't be added (in this example you shouldn't add anything as no complete page is covered by the range).
You need something like:
end = (start + size) & PAGE_MASK; start = PAGE_ALIGN(start); size = end - start; if (!size) return;
Juergen
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