[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] x86/hvm: honor guest's option when updating secondary system time for guest
> -----Original Message----- > From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > Sent: Wednesday, July 23, 2014 8:19 PM > To: Wu, Feng > Cc: linux@xxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; konrad.wilk@xxxxxxxxxx; > keir@xxxxxxx; tim@xxxxxxx > Subject: Re: [PATCH 2/2] x86/hvm: honor guest's option when updating > secondary system time for guest > > >>> On 08.07.14 at 01:18, <feng.wu@xxxxxxxxx> wrote: > > --- a/xen/include/public/vcpu.h > > +++ b/xen/include/public/vcpu.h > > @@ -227,6 +227,16 @@ struct vcpu_register_time_memory_area { > > typedef struct vcpu_register_time_memory_area > > vcpu_register_time_memory_area_t; > > DEFINE_XEN_GUEST_HANDLE(vcpu_register_time_memory_area_t); > > > > +/* > > + * Flags to tell Xen whether we need to do the SMAP check when updating > > + * the secondary copy of the vcpu time when SMAP is enabled. Since the > > + * memory location for the secondary copy of the vcpu time may be mapped > > + * into userspace by guests intendedly, we let the guest to determine > > + * whether the check is needed. The default behavior of hypevisor is > > + * not doing the check. > > + */ > > +#define VCPUOP_enable_smap_check_vcpu_time_memory_area 14 > > I think the new op to be VCPUOP_register_vcpu_time_memory_area_smap, > identical to VCPUOP_register_vcpu_time_memory_area apart from also > setting the flag, would be more natural. But considering what I just wrote > in the reply to Tim I guess we can expect a nun-user mapping to be > presented here anyway, i.e. we wouldn't need to new operation at all. Do you mean since the user-paging is r/o, guest will pass a r/w kernel page to Xen for updating the system time. So we don't need to do the SMAP check in this case? Thanks, Feng > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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