On 10/02/2026 11:55 am, Jan Beulich wrote: > On 10.02.2026 12:15, Andrew Cooper wrote: >> On 07/10/2025 4:58 pm, Jan Beulich wrote: >>> On 04.10.2025 00:53, Andrew Cooper wrote: >>>> FRED and IDT differ by a Supervisor Token on the base of the shstk. This >>>> means that switch_stack_and_jump() needs to discard one extra word when >>>> FRED >>>> is active. >>>> >>>> Fix a typo in the parameter name, which should be shstk_base. >>>> >>>> Signed-off-by: Andrew Cooper <[email protected]> >>>> Reviewed-by: Jan Beulich <[email protected]> >>>> --- >>>> CC: Jan Beulich <[email protected]> >>>> CC: Roger Pau Monné <[email protected]> >>>> >>>> Leave as $%c. Otherwise it doesn't assemble correctly presented with >>>> $$24568 >>>> to parse as an instruction immediate. >>> I don't follow. Where would the 2nd $ come from if you write ... >>> >>>> --- a/xen/arch/x86/include/asm/current.h >>>> +++ b/xen/arch/x86/include/asm/current.h >>>> @@ -154,7 +154,9 @@ unsigned long get_stack_dump_bottom (unsigned long sp); >>>> "rdsspd %[ssp];" \ >>>> "cmp $1, %[ssp];" \ >>>> "je .L_shstk_done.%=;" /* CET not active? Skip. */ \ >>>> - "mov $%c[skstk_base], %[val];" \ >>>> + ALTERNATIVE("mov $%c[shstk_base], %[val];", \ >>>> + "mov $%c[shstk_base] + 8, %[val];", \ >>>> + X86_FEATURE_XEN_FRED) \ >>> ALTERNATIVE("mov %[shstk_base], %[val];", \ >>> "mov %[shstk_base] + 8, %[val];", \ >>> X86_FEATURE_XEN_FRED) \ >> I find this feedback completely uncharacteristic. You always goes out >> of your way to hide % inside macros to prohibit non-register operands. >> >> This is exactly the same, except to force an immediate operand, so the >> length of the two instructions is the same. > Thinking about it more, are you perhaps referring to assembler macros? > There indeed I prefer to have the % inside the macros; the same may go > for $ there, but I don't think we had the need so far. For inline > assembly the situation is different: The compiler emits the % (and also > the $), unless special modifiers are used. It wouldn't even occur to me > to ask that we use %%%V[val] for a register operand. That really is the > register equivalent of the $%c[val] that you use above.
We can't use %V anyway because it's not available in our toolchain baseline. But, bottom line. How insistent are you going to be here, because this is the only thing holding up committing 6 patches. ~Andrew
