On 3/24/25 1:31 PM, Jan Beulich wrote:
On 21.03.2025 17:17, Oleksii Kurochko wrote:
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 it will be needed to encode H extensions instructions
explicitly by checking if __risv_h is defined.
Leaving aside the typo, what is this about? There's no use of __riscv_h in
the patch here, and ...
It is going to be used in future
patches:https://gitlab.com/xen-project/people/olkur/xen/-/blob/riscv-next-upstreaming/xen/arch/riscv/p2m.c?ref_type=heads#L32
@@ -25,10 +24,13 @@ $(eval $(1) := \
$(call as-insn,$(CC) $(riscv-generic-flags)_$(1),$(value
$(1)-insn),_$(1)))
endef
+h-insn := "hfence.gvma"
+$(call check-extension,h)
... this, if it fails, will not have any effect on the build right now
afaics.
No, it won't have any affect now as instruction from H extension isn't used now.
But it will be needed
forhttps://lore.kernel.org/xen-devel/dae753618491b2a6e42f7ed3f24190d0dc13fe3f.1740754166.git.slavisa.petro...@rt-rk.com/
and for p2m changes mentioned above.
~ Oleksii
