| Message ID | 32ebe4032b7968157d5cadbc2f6aa1d9f2d363c9.1741707803.git.oleksii.kurochko@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v1] xen/riscv: add H extenstion to -march | expand |
On 11.03.2025 16:45, Oleksii Kurochko wrote: > --- a/xen/arch/riscv/arch.mk > +++ b/xen/arch/riscv/arch.mk > @@ -9,7 +9,8 @@ riscv-abi-$(CONFIG_RISCV_64) := -mabi=lp64 > riscv-march-$(CONFIG_RISCV_64) := rv64 > riscv-march-y += ima > riscv-march-$(CONFIG_RISCV_ISA_C) += c > -riscv-march-y += _zicsr_zifencei_zbb > +h-extension-name := $(call cc-ifversion,-lt,1301, hh, h) Instead of a version check, did you consider probing the compiler? With the hard-coded version, how are things going to work with Clang? Jan
On 3/11/25 4:48 PM, Jan Beulich wrote: > On 11.03.2025 16:45, Oleksii Kurochko wrote: >> --- a/xen/arch/riscv/arch.mk >> +++ b/xen/arch/riscv/arch.mk >> @@ -9,7 +9,8 @@ riscv-abi-$(CONFIG_RISCV_64) := -mabi=lp64 >> riscv-march-$(CONFIG_RISCV_64) := rv64 >> riscv-march-y += ima >> riscv-march-$(CONFIG_RISCV_ISA_C) += c >> -riscv-march-y += _zicsr_zifencei_zbb >> +h-extension-name := $(call cc-ifversion,-lt,1301, hh, h) > Instead of a version check, did you consider probing the compiler? With the > hard-coded version, how are things going to work with Clang? Initially, it was implemented using: +$(h-extension-name)-insn := "hfence.gvma" +$(call check-extension,$(h-extension-name)) with +h-extension-name := $(call cc-ifversion,-lt,1301, hh, h) But it seems that we still need this hard-coded version for h-extension-name because of this behavior that h extensions should be longer then single letter for some compilers. Probably, we could consider option to check "hfence.gvma" twice: h-insn := "hfence.gvma" $(call check-extension,h) hh-insn := "hfence.gvma" $(call check-extension,hh) And filter-out/skip the second check-extension if the previous one check succeeded. But it looks a weird. ~ Oleksii
diff --git a/docs/misc/riscv/booting.txt b/docs/misc/riscv/booting.txt index cb4d79f12c..3a8474a27d 100644 --- a/docs/misc/riscv/booting.txt +++ b/docs/misc/riscv/booting.txt @@ -3,6 +3,10 @@ System requirements The following extensions are expected to be supported by a system on which Xen is run: +- H: + Provides additional instructions and CSRs that control the new stage of + address translation and support hosting a guest OS in virtual S-mode + (VS-mode). - Zbb: RISC-V doesn't have a CLZ instruction in the base ISA. As a consequence, __builtin_ffs() emits a library call to ffs() on GCC, diff --git a/xen/arch/riscv/arch.mk b/xen/arch/riscv/arch.mk index 236ea7c8a6..14d1f0ada0 100644 --- a/xen/arch/riscv/arch.mk +++ b/xen/arch/riscv/arch.mk @@ -9,7 +9,8 @@ riscv-abi-$(CONFIG_RISCV_64) := -mabi=lp64 riscv-march-$(CONFIG_RISCV_64) := rv64 riscv-march-y += ima riscv-march-$(CONFIG_RISCV_ISA_C) += c -riscv-march-y += _zicsr_zifencei_zbb +h-extension-name := $(call cc-ifversion,-lt,1301, hh, h) +riscv-march-y += $(h-extension-name)_zicsr_zifencei_zbb riscv-generic-flags := $(riscv-abi-y) -march=$(subst $(space),,$(riscv-march-y)) diff --git a/xen/arch/riscv/cpufeature.c b/xen/arch/riscv/cpufeature.c index bf09aa1170..5aafab0f49 100644 --- a/xen/arch/riscv/cpufeature.c +++ b/xen/arch/riscv/cpufeature.c @@ -146,6 +146,7 @@ static const struct riscv_isa_ext_data __initconst required_extensions[] = { #ifdef CONFIG_RISCV_ISA_C RISCV_ISA_EXT_DATA(c), #endif + RISCV_ISA_EXT_DATA(h), RISCV_ISA_EXT_DATA(zicsr), RISCV_ISA_EXT_DATA(zifencei), RISCV_ISA_EXT_DATA(zihintpause),
H provides additional instructions and CSRs that control the new stage of address translation and support hosting a guest OS in virtual S-mode (VS-mode). According to the Unprivileged Architecture (version 20240411) specification: ``` Table 74 summarizes the standardized extension names. The table also defines the canonical order in which extension names must appear in the name string, with top-to-bottom in table indicating first-to-last in the name string, e.g., RV32IMACV is legal, whereas RV32IMAVC is not. ``` According to Table 74, the h extension is placed last in the one-letter extensions name part of the ISA string. `h` is a standalone extension based on the patch [1] but it wasn't so before. As the minimal supported GCC version to build Xen for RISC-V is 12.2.0, and for that version, h is still considered a prefix for the hypervisor extension but the name of hypervisor extension must be more then 1 letter extension, a workaround ( with using `hh` as an H extension name ) is implemented as otherwise the following compilation error will occur: error: '-march=rv64gc_h_zbb_zihintpause': name of hypervisor extension must be more than 1 letter After GCC version 13.1.0, the commit [1] introducing H extension support allows us to drop the workaround with `hh` as hypervisor extension name and use only one h in -march. To implement this, the h-extension-name is introduced, which is filled with hh or h depending on the GCC version. [1] https://github.com/gcc-mirror/gcc/commit/0cd11d301013af50a3fae0694c909952e94e20d5#diff-d6f7db0db31bfb339b01bec450f1b905381eb4730cc5ab2b2794971e34647d64R148 Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com> --- docs/misc/riscv/booting.txt | 4 ++++ xen/arch/riscv/arch.mk | 3 ++- xen/arch/riscv/cpufeature.c | 1 + 3 files changed, 7 insertions(+), 1 deletion(-)