Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH] xen/p2m: fix extra memory regions accounting | From | Juergen Gross <> | Date | Thu, 3 Sep 2015 16:55:14 +0200 |
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On 09/03/2015 04:52 PM, David Vrabel wrote: > On 03/09/15 15:45, David Vrabel wrote: >> On 03/09/15 15:38, 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). >> >> We expand the reserved (i.e., non-RAM) areas down so they're fully >> covered with whole pages when we depopulate and 1:1 map them, we should >> add extra memory regions that cover these same areas. > > Ignore this. This was nonsense. > > We expand the reserved (i.e., non-RAM) areas so they're fully covered > with whole pages when we depopulate and 1:1 map them, we should add the > extra memory such that it does not overlap with with expanded regions. > i.e., round up the start and round down the end (like Roger's patch does).
Nearly. Roger's patch rounds up start and rounds down the size. It might add non-RAM partial pages to xen_extra_mem.
Juergen
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