On 07.11.25 08:52, Jan Beulich wrote:
On 06.11.2025 23:26, Grygorii Strashko wrote:
From: Grygorii Strashko <[email protected]>
Xen uses below pattern for raw_x_guest() functions:
define raw_copy_to_guest(dst, src, len) \
(is_hvm_vcpu(current) ? \
copy_to_user_hvm((dst), (src), (len)) : \
copy_to_guest_pv(dst, src, len))
This pattern works depending on CONFIG_PV/CONFIG_HVM as:
- PV=y and HVM=y
Proper guest access function is selected depending on domain type.
- PV=y and HVM=n
Only PV domains are possible. is_hvm_domain/vcpu() will constify to "false"
and compiler will optimize code and skip HVM specific part.
- PV=n and HVM=y
Only HVM domains are possible. is_hvm_domain/vcpu() will not be constified.
No PV specific code will be optimized by compiler.
- PV=n and HVM=n
No guests should possible. The code will still follow PV path.
Rework raw_x_guest() code to use static inline functions which account for
above PV/HVM possible configurations with main intention to optimize code
for (PV=n and HVM=y) case.
For the case (PV=n and HVM=n) return "len" value indicating a failure (no
guests should be possible in this case, which means no access to guest
memory should ever happen).
Finally build arch/x86/usercopy.c only for PV=y.
The measured (bloat-o-meter) improvement for (PV=n and HVM=y) case is:
add/remove: 2/9 grow/shrink: 2/90 up/down: 1678/-32560 (-30882)
Total: Before=1937092, After=1906210, chg -1.59%
Signed-off-by: Grygorii Strashko <[email protected]>
[[email protected]: Suggested to use static inline functions vs macro
combinations]
Suggested-by: Teddy Astie <[email protected]>
Just one formal request for now: Please send patches To: the list, with
individuals
on Cc: as necessary.
Sure, sorry.
--
Best regards,
-grygorii
