On Tue, Jul 14, 2020 at 11:17:01PM +0800, Zhenyu Ye wrote: > On 2020/7/14 0:59, Catalin Marinas wrote: > >> +config ARM64_TLBI_RANGE > >> + bool "Enable support for tlbi range feature" > >> + default y > >> + depends on AS_HAS_TLBI_RANGE > >> + help > >> + ARMv8.4-TLBI provides TLBI invalidation instruction that apply to a > >> + range of input addresses. > >> + > >> + The feature introduces new assembly instructions, and they were > >> + support when binutils >= 2.30. > > > > It looks like 2.30. I tracked it down to this commit: > > > > https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=793a194839bc8add71fdc7429c58b10f0667a6f6;hp=1a7ed57c840dcb0401f1a67c6763a89f7d2686d2 > > > >> +config AS_HAS_TLBI_RANGE > >> + def_bool $(as-option, -Wa$(comma)-march=armv8.4-a) You could make this more generic like AS_HAS_ARMV8_4. > > The problem is that we don't pass -Wa,-march=armv8.4-a to gas. AFAICT, > > we only set an 8.3 for PAC but I'm not sure how passing two such options > > goes. > > Pass the -march twice may not have bad impact. Test in my toolchains > and the newer one will be chosen. Anyway, we can add judgment to avoid > them be passed at the same time. I think the last one always overrides the previous (same with the .arch statements in asm files). For example: echo "paciasp" | aarch64-none-linux-gnu-as -march=armv8.2-a -march=armv8.3-a succeeds but the one below fails: echo "paciasp" | aarch64-none-linux-gnu-as -march=armv8.3-a -march=armv8.2-a > > A safer bet may be to simply encode the instructions by hand: > > > > #define SYS_TLBI_RVAE1IS(Rt) \ > > __emit_inst(0xd5000000 | sys_insn(1, 0, 8, 2, 1) | ((Rt) & 0x1f)) > > #define SYS_TLBI_RVALE1IS(Rt) \ > > __emit_inst(0xd5000000 | sys_insn(1, 0, 8, 2, 5) | ((Rt) & 0x1f)) > > > > (please check that they are correct) > > Currently in kernel, all tlbi instructions are passed through __tlbi() > and __tlbi_user(). If we encode the range instructions by hand, we may > should have to add a new mechanism for this: > > 1. choose a register and save it; > 2. put the operations for tlbi range to the register; > 3. do tlbi range by asm(SYS_TLBI_RVAE1IS(x0)); > 4. restore the value of the register. > > It's complicated and will only be used with tlbi range instructions. > (Am I understand something wrong? ) > > So I am prefer to pass -march=armv8.4-a to toolschains to support tlbi > range instruction, just like what PAC does. It will indeed get more complicated than necessary. So please go with the -Wa,-march=armv8.4-a check in Kconfig and update the arch/arm64/Makefile to pass this option (after the 8.3 one). Thanks. -- Catalin
