[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
At 07:18 +0800 on 08 Jul (1404800298), Feng Wu wrote: > In this patch, we add a new hypervisor which allows guests to enable > SMAP check when Xen is updating the secondary system time for guest. > The SMAP check for this update is disabled by default. Again, it seems like we should never do SMAP checks here, since (a) this is a hypervisor operation, totally independent of whether the vcpu is in user mode or not, (b) this happens asynchronously to the guest so we can't raise a fault, an (c) this is explicitly _supposed_ to access a user-space mapping. Tim. > Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx> > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx> > --- > xen/arch/x86/domain.c | 6 ++++++ > xen/arch/x86/hvm/hvm.c | 2 ++ > xen/arch/x86/time.c | 12 +++++++++++- > xen/include/asm-x86/domain.h | 9 ++++++++- > xen/include/public/vcpu.h | 10 ++++++++++ > 5 files changed, 37 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c > index b0c8810..a787c46 100644 > --- a/xen/arch/x86/domain.c > +++ b/xen/arch/x86/domain.c > @@ -1053,6 +1053,12 @@ arch_do_vcpu_op( > break; > } > > + case VCPUOP_enable_smap_check_vcpu_time_memory_area: > + { > + v->arch.enable_smap_check = 1; > + break; > + } > + > case VCPUOP_get_physid: > { > struct vcpu_get_physid cpu_id; > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c > index ef2411c..a922711 100644 > --- a/xen/arch/x86/hvm/hvm.c > +++ b/xen/arch/x86/hvm/hvm.c > @@ -4629,6 +4629,7 @@ static long hvm_vcpu_op( > case VCPUOP_stop_singleshot_timer: > case VCPUOP_register_vcpu_info: > case VCPUOP_register_vcpu_time_memory_area: > + case VCPUOP_enable_smap_check_vcpu_time_memory_area: > rc = do_vcpu_op(cmd, vcpuid, arg); > break; > default: > @@ -4688,6 +4689,7 @@ static long hvm_vcpu_op_compat32( > case VCPUOP_stop_singleshot_timer: > case VCPUOP_register_vcpu_info: > case VCPUOP_register_vcpu_time_memory_area: > + case VCPUOP_enable_smap_check_vcpu_time_memory_area: > rc = compat_vcpu_op(cmd, vcpuid, arg); > break; > default: > diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c > index a4e1656..338381e 100644 > --- a/xen/arch/x86/time.c > +++ b/xen/arch/x86/time.c > @@ -821,7 +821,7 @@ static void __update_vcpu_system_time(struct vcpu *v, int > force) > v->arch.pv_vcpu.pending_system_time = _u; > } > > -bool_t update_secondary_system_time(const struct vcpu *v, > +bool_t update_secondary_system_time(struct vcpu *v, > struct vcpu_time_info *u) > { > XEN_GUEST_HANDLE(vcpu_time_info_t) user_u = v->arch.time_info_guest; > @@ -829,9 +829,16 @@ bool_t update_secondary_system_time(const struct vcpu *v, > if ( guest_handle_is_null(user_u) ) > return 1; > > + if ( v->arch.enable_smap_check ) > + v->arch.smap_check_policy = SMAP_CHECK_ENABLED; > + ¼> /* 1. Update userspace version. */ > if ( __copy_field_to_guest(user_u, u, version) == sizeof(u->version) ) > + { > + if ( v->arch.enable_smap_check ) > + v->arch.smap_check_policy = SMAP_CHECK_HONOR_CPL_AC; > return 0; > + } > wmb(); > /* 2. Update all other userspace fields. */ > __copy_to_guest(user_u, u, 1); > @@ -840,6 +847,9 @@ bool_t update_secondary_system_time(const struct vcpu *v, > u->version = version_update_end(u->version); > __copy_field_to_guest(user_u, u, version); > > + if ( v->arch.enable_smap_check ) > + v->arch.smap_check_policy = SMAP_CHECK_HONOR_CPL_AC; > + > return 1; > } > > diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h > index d7cac4f..051fed0 100644 > --- a/xen/include/asm-x86/domain.h > +++ b/xen/include/asm-x86/domain.h > @@ -455,6 +455,13 @@ struct arch_vcpu > * SMAP_CHECK_DISABLED - disable the check > */ > uint8_t smap_check_policy; > + > + /* > + * This is a flag to indicate that whether the guest wants to enable > + * SMAP check when Xen is updating the secondary system time from it. > + */ > + bool_t enable_smap_check; > + uint16_t pad; > } __cacheline_aligned; > > #define SMAP_CHECK_HONOR_CPL_AC 0 > @@ -466,7 +473,7 @@ struct arch_vcpu > #define hvm_svm hvm_vcpu.u.svm > > bool_t update_runstate_area(struct vcpu *); > -bool_t update_secondary_system_time(const struct vcpu *, > +bool_t update_secondary_system_time(struct vcpu *, > struct vcpu_time_info *); > > void vcpu_show_execution_state(struct vcpu *); > diff --git a/xen/include/public/vcpu.h b/xen/include/public/vcpu.h > index e888daf..d348395 100644 > --- 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 > + > #endif /* __XEN_PUBLIC_VCPU_H__ */ > > /* > -- > 1.8.3.1 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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