[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: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx] > Sent: Tuesday, July 08, 2014 6:08 PM > To: Wu, Feng; xen-devel@xxxxxxxxxxxxx > Cc: tim@xxxxxxx; linux@xxxxxxxxxxxxxx; jbeulich@xxxxxxxx; keir@xxxxxxx > Subject: Re: [Xen-devel] [PATCH 2/2] x86/hvm: honor guest's option when > updating secondary system time for guest > > On 08/07/14 00:18, 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. > > > > Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx> > > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx> > > This patch uses the same v->arch.smap_check_policy variable as the > previous patch, meaning its value is unconditionally > SMAP_CHECK_HONOR_CPL_AC other than the short window while the > runstate > area is being updated. Guests can enable it by hypercall ' VCPUOP_enable_smap_check_vcpu_time_memory_area ', If the guest calls this hypercall, v->arch.enable_smap_check will be set to 1, so when updating the secondary system time for guest, v->arch.smap_check_policy will be set to SMAP_CHECK_ENABLED. Thanks, Feng > > As a result, there appears to be no way for this to cause working > updates to a system time living in guest userspace. > > ~Andrew > > > --- > > 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; > > + > > /* 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__ */ > > > > /* _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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