Messages in this thread | | | Subject | Re: [PATCH] xen/p2m: fix extra memory regions accounting | From | Roger Pau Monné <> | Date | Thu, 3 Sep 2015 16:38:25 +0200 |
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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).
Roger.
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