Messages in this thread | | | Date | Fri, 17 Jul 2015 13:52:12 -0400 | From | Boris Ostrovsky <> | Subject | Re: [PATCH v2 4/6] xen/x86/pvh: Set up descriptors for 32-bit PVH guests |
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On 07/17/2015 12:43 PM, Konrad Rzeszutek Wilk wrote: > On Fri, Jul 17, 2015 at 11:36:29AM -0400, Boris Ostrovsky wrote: >> On 07/17/2015 11:21 AM, Konrad Rzeszutek Wilk wrote: >>> On Thu, Jul 16, 2015 at 05:43:39PM -0400, Boris Ostrovsky wrote: >>>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> >>>> --- >>>> Changes in v2: >>>> * Set segment selectors using loadsegment() instead of assembly >>>> >>>> arch/x86/xen/enlighten.c | 15 ++++++++++----- >>>> 1 file changed, 10 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c >>>> index f8dc398..d665b1d 100644 >>>> --- a/arch/x86/xen/enlighten.c >>>> +++ b/arch/x86/xen/enlighten.c >>>> @@ -1362,12 +1362,12 @@ static void __init xen_boot_params_init_edd(void) >>>> static void __ref xen_setup_gdt(int cpu) >>>> { >>>> if (xen_feature(XENFEAT_auto_translated_physmap)) { >>>> -#ifdef CONFIG_X86_64 >>>> - unsigned long dummy; >>>> + unsigned long __attribute__((unused)) dummy; >>>> - load_percpu_segment(cpu); /* We need to access per-cpu area */ >>> You removed that - where are we going to do that? As the >>> 'switch_to_new_gdt' uses the per-cpu GDT table. >> load_percpu_segment() is part of switch_to_new_gdt(), so I thought there is >> no need to call it here. >> >> But you are right --- switch_to_new_gdt() starts with get_cpu_gdt_table() >> which accesses per-CPU area. How did this manage to work then? > I was surprised as well - I was expecting your patch to have blow up. > Unless we are doing something fancy for CPU0 and for the other CPUs we > already have the per-cpu segment setup during bootup (copied from BSP)?
No, %fs is zero when we enter xen_setup_gdt() (for 32-bit).
In any case, I should put load_percpu_segment() back.
-boris
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