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[RFC PATCH] target/riscv: Add Zihintntl extension ISA string to DTS

From: Jason Chien
Subject: [RFC PATCH] target/riscv: Add Zihintntl extension ISA string to DTS
Date: Tue, 27 Jun 2023 09:26:29 +0000

RVA23 Profiles states:
The RVA23 profiles are intended to be used for 64-bit application
processors that will run rich OS stacks from standard binary OS
distributions and with a substantial number of third-party binary user
applications that will be supported over a considerable length of time
in the field.

The chapter 4 of the unprivileged spec introduces the Zihintntl extension
and Zihintntl is a mandatory extension presented in RVA23 Profiles, whose
targeting software stacks includes Linux. Thus the DTS should contain
the Zihintntl ISA string in order to pass to Linux.

The unprivileged spec states:
Like any HINTs, these instructions may be freely ignored. Hence, although
they are described in terms of cache-based memory hierarchies, they do not
mandate the provision of caches.

These instructions are encoded with used opcode, which QEMU already
supports, and QEMU does not emulate cache, therefore we just need to add
a new property for the extension.

Signed-off-by: Jason Chien <jason.chien@sifive.com>
 target/riscv/cpu.c     | 2 ++
 target/riscv/cpu_cfg.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 881bddf393..aa99781f17 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -81,6 +81,7 @@ static const struct isa_ext_data isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zicond, PRIV_VERSION_1_12_0, ext_zicond),
     ISA_EXT_DATA_ENTRY(zicsr, PRIV_VERSION_1_10_0, ext_icsr),
     ISA_EXT_DATA_ENTRY(zifencei, PRIV_VERSION_1_10_0, ext_ifencei),
+    ISA_EXT_DATA_ENTRY(zihintntl, PRIV_VERSION_1_10_0, ext_zihintntl),
     ISA_EXT_DATA_ENTRY(zihintpause, PRIV_VERSION_1_10_0, ext_zihintpause),
     ISA_EXT_DATA_ENTRY(zawrs, PRIV_VERSION_1_12_0, ext_zawrs),
     ISA_EXT_DATA_ENTRY(zfh, PRIV_VERSION_1_11_0, ext_zfh),
@@ -1598,6 +1599,7 @@ static Property riscv_cpu_extensions[] = {
     DEFINE_PROP_BOOL("sscofpmf", RISCVCPU, cfg.ext_sscofpmf, false),
     DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
     DEFINE_PROP_BOOL("Zicsr", RISCVCPU, cfg.ext_icsr, true),
+    DEFINE_PROP_BOOL("Zihintntl", RISCVCPU, cfg.ext_zihintntl, false),
     DEFINE_PROP_BOOL("Zihintpause", RISCVCPU, cfg.ext_zihintpause, true),
     DEFINE_PROP_BOOL("Zawrs", RISCVCPU, cfg.ext_zawrs, true),
     DEFINE_PROP_BOOL("Zfh", RISCVCPU, cfg.ext_zfh, false),
diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
index c4a627d335..c7da2facef 100644
--- a/target/riscv/cpu_cfg.h
+++ b/target/riscv/cpu_cfg.h
@@ -66,6 +66,7 @@ struct RISCVCPUConfig {
     bool ext_icbom;
     bool ext_icboz;
     bool ext_zicond;
+    bool ext_zihintntl;
     bool ext_zihintpause;
     bool ext_smstateen;
     bool ext_sstc;

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