Re: [XEN][PATCH 0/8] xen/arm64: make aarch32 support optional

[Grygorii Strashko <grygorii_strashko@xxxxxxxx>]

On 23.07.25 13:54, Orzel, Michal wrote:
> On 23/07/2025 10:06, Julien Grall wrote:
> > On 23/07/2025 08:58, Grygorii Strashko wrote:
> > > From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
> > >
> > > Hi,
> > Hi Grygorii,
> >
> > > Now Arm64 AArch32 guest support is always enabled and built-in while not
> > > all Arm64 platforms supports AArch32 or this support might not be needed.
> > I am not entirely sure I like the proliferation of using CONFIG_* for
> > every single feature. This makes the testing a bit more complicated.
> >
> > Can you clarify what the goal with this patch?
> AArch32 is used quite rarely in embedded systems. Also, in Armv9A it might only
> be implemented at EL0 if at all. When focusing on safety certification, AArch32
> related code in Xen leaves a gap in terms of coverage that cannot really be
> justified in words. This leaves us with two options: either support it (lots of
> additional testing, requirements and documents would be needed) or compile it 
> out.
FYI. bloat-o-meter report for this series with CONFIG_ARM64_AARCH32=n, 
CONFIG_EXPERT=y

add/remove: 0/6 grow/shrink: 2/32 up/down: 276/-5672 (-5396)
Function                                     old     new   delta
do_trap_guest_sync                          1588    1856    +268
start_xen                                   2456    2464      +8
make_cpus_node                               832     820     -12
arch_vcpu_create                             328     312     -16
vfp_save_state                               132     112     -20
vfp_restore_state                            132     112     -20
is_guest_pv32_psr                             20       -     -20
construct_hwdom                             1208    1188     -20
construct_domU                              2544    2524     -20
make_hypervisor_node                        2048    2016     -32
inject_undef64_exception                     112      80     -32
inject_abt64_exception                       164     132     -32
show_registers                               260     224     -36
arm64_set_domain_type                        128      88     -40
do_deprecated_hypercall                      124      80     -44
construct_domain                             316     272     -44
init_xen_cap_info                             96      44     -52
continue_new_vcpu                            188     136     -52
check_conditional_instr                      192     140     -52
vsmccc_handle_call                          1328    1272     -56
make_timer_node                              492     436     -56
vcpu_regs_user_to_hyp                        512     448     -64
vcpu_regs_hyp_to_user                        512     448     -64
do_common_cpu_on                             440     372     -68
cpsr_switch_mode                              80       -     -80
advance_pc                                   140      32    -108
do_trap_stage2_abort_guest                   836     724    -112
arch_set_info_guest                          336     184    -152
inject_undef_exception                       180      20    -160
arch_do_multicall_call                       632     468    -164
schedule_tail                                752     576    -176
decode_thumb2                                200       -    -200
subarch_do_domctl                            276      40    -236
inject_abt32_exception                       236       -    -236
do_debug_trap                                256       -    -256
hypercall_create_continuation               1228     848    -380
_show_registers                              832     380    -452
decode_instruction                          1032     476    -556
do_trap_hypercall                            640       -    -640
guest_walk_tables                           1896     984    -912
Total: Before=670920, After=665524, chg -0.80%
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
Data                                         old     new   delta
Total: Before=448625, After=448625, chg +0.00%
add/remove: 0/0 grow/shrink: 1/0 up/down: 191/0 (191)
RO Data                                      old     new   delta
xen_config_data                             1345    1536    +191
Total: Before=18498, After=18689, chg +1.03%

--
Best regards,
-grygorii