Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH] xen/p2m: fix extra memory regions accounting | From | Juergen Gross <> | Date | Thu, 3 Sep 2015 17:20:42 +0200 |
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On 09/03/2015 05:01 PM, David Vrabel wrote: > On 03/09/15 15:55, Juergen Gross wrote: >> 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. > > Yes. You're right.
Hmm, thinking more about it, I'd prefer to change xen_extra_mem to use pfns instead of physical addresses. This would make things much more clear.
Roger, do you want to do the patch or should I?
Juergen
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