[PATCH v2 15/18] target/riscv: make riscv_isa_string_ext() KVM compatible

[Daniel Henrique Barboza <dbarboza@ventanamicro.com>]

The isa_edata_arr[] is used by riscv_isa_string_ext() to create the
riscv,isa DT attribute. isa_edata_arr[] is kept in sync with the TCG
property vector riscv_cpu_extensions[], i.e. all TCG properties from
this vector that has a riscv,isa representation are included in
isa_edata_arr[].

KVM doesn't implement all TCG properties, but allow them to be created
anyway to not force an API change between TCG and KVM guests. Some of
these TCG-only extensions are defaulted to 'true', and users are also
allowed to enable them. KVM doesn't care, but riscv_isa_string_ext()
does. The result is that these TCG-only enabled extensions will appear
in the riscv,isa DT string under KVM.

To avoid code repetition and re-use riscv_isa_string_ext() for KVM
guests we'll make a couple of tweaks:

- set env->priv_ver to 'LATEST' for the KVM 'host' CPU. This is needed
  because riscv_isa_string_ext() makes a priv check for each extension
  before including them in the ISA string. KVM doesn't care about
  env->priv_ver, since it's part of the TCG-only CPU validation, so this
  change is benign for KVM;

- add a new 'kvm_available' flag in isa_ext_data struct. This flag is
  set via a new ISA_EXT_DATA_ENTRY_KVM macro to report that, for a given
  extension, KVM also supports it. riscv_isa_string_ext() then can check
  if a given extension is known by KVM and skip it if it's not.

This will allow us to re-use riscv_isa_string_ext() for KVM guests.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index a4f3ed0c17..a773c09645 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -44,11 +44,15 @@ struct isa_ext_data {
     const char *name;
     int min_version;
     int ext_enable_offset;
+    bool kvm_available;
 };
 
 #define ISA_EXT_DATA_ENTRY(_name, _min_ver, _prop) \
     {#_name, _min_ver, offsetof(struct RISCVCPUConfig, _prop)}
 
+#define ISA_EXT_DATA_ENTRY_KVM(_name, _min_ver, _prop) \
+    {#_name, _min_ver, offsetof(struct RISCVCPUConfig, _prop), true}
+
 /*
  * Here are the ordering rules of extension naming defined by RISC-V
  * specification :
@@ -68,14 +72,17 @@ struct isa_ext_data {
  *
  * Single letter extensions are checked in riscv_cpu_validate_misa_priv()
  * instead.
+ *
+ * ISA_EXT_DATA_ENTRY_KVM() is used to indicate that the extension is
+ * also known by the KVM driver. If unsure, use ISA_EXT_DATA_ENTRY().
  */
 static const struct isa_ext_data isa_edata_arr[] = {
-    ISA_EXT_DATA_ENTRY(zicbom, PRIV_VERSION_1_12_0, ext_icbom),
-    ISA_EXT_DATA_ENTRY(zicboz, PRIV_VERSION_1_12_0, ext_icboz),
+    ISA_EXT_DATA_ENTRY_KVM(zicbom, PRIV_VERSION_1_12_0, ext_icbom),
+    ISA_EXT_DATA_ENTRY_KVM(zicboz, PRIV_VERSION_1_12_0, ext_icboz),
     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(zihintpause, PRIV_VERSION_1_10_0, ext_zihintpause),
+    ISA_EXT_DATA_ENTRY_KVM(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),
     ISA_EXT_DATA_ENTRY(zfhmin, PRIV_VERSION_1_11_0, ext_zfhmin),
@@ -89,7 +96,7 @@ static const struct isa_ext_data isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zcmp, PRIV_VERSION_1_12_0, ext_zcmp),
     ISA_EXT_DATA_ENTRY(zcmt, PRIV_VERSION_1_12_0, ext_zcmt),
     ISA_EXT_DATA_ENTRY(zba, PRIV_VERSION_1_12_0, ext_zba),
-    ISA_EXT_DATA_ENTRY(zbb, PRIV_VERSION_1_12_0, ext_zbb),
+    ISA_EXT_DATA_ENTRY_KVM(zbb, PRIV_VERSION_1_12_0, ext_zbb),
     ISA_EXT_DATA_ENTRY(zbc, PRIV_VERSION_1_12_0, ext_zbc),
     ISA_EXT_DATA_ENTRY(zbkb, PRIV_VERSION_1_12_0, ext_zbkb),
     ISA_EXT_DATA_ENTRY(zbkc, PRIV_VERSION_1_12_0, ext_zbkc),
@@ -114,13 +121,13 @@ static const struct isa_ext_data isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zhinxmin, PRIV_VERSION_1_12_0, ext_zhinxmin),
     ISA_EXT_DATA_ENTRY(smaia, PRIV_VERSION_1_12_0, ext_smaia),
     ISA_EXT_DATA_ENTRY(smstateen, PRIV_VERSION_1_12_0, ext_smstateen),
-    ISA_EXT_DATA_ENTRY(ssaia, PRIV_VERSION_1_12_0, ext_ssaia),
+    ISA_EXT_DATA_ENTRY_KVM(ssaia, PRIV_VERSION_1_12_0, ext_ssaia),
     ISA_EXT_DATA_ENTRY(sscofpmf, PRIV_VERSION_1_12_0, ext_sscofpmf),
-    ISA_EXT_DATA_ENTRY(sstc, PRIV_VERSION_1_12_0, ext_sstc),
+    ISA_EXT_DATA_ENTRY_KVM(sstc, PRIV_VERSION_1_12_0, ext_sstc),
     ISA_EXT_DATA_ENTRY(svadu, PRIV_VERSION_1_12_0, ext_svadu),
-    ISA_EXT_DATA_ENTRY(svinval, PRIV_VERSION_1_12_0, ext_svinval),
+    ISA_EXT_DATA_ENTRY_KVM(svinval, PRIV_VERSION_1_12_0, ext_svinval),
     ISA_EXT_DATA_ENTRY(svnapot, PRIV_VERSION_1_12_0, ext_svnapot),
-    ISA_EXT_DATA_ENTRY(svpbmt, PRIV_VERSION_1_12_0, ext_svpbmt),
+    ISA_EXT_DATA_ENTRY_KVM(svpbmt, PRIV_VERSION_1_12_0, ext_svpbmt),
     ISA_EXT_DATA_ENTRY(xtheadba, PRIV_VERSION_1_11_0, ext_xtheadba),
     ISA_EXT_DATA_ENTRY(xtheadbb, PRIV_VERSION_1_11_0, ext_xtheadbb),
     ISA_EXT_DATA_ENTRY(xtheadbs, PRIV_VERSION_1_11_0, ext_xtheadbs),
@@ -586,6 +593,7 @@ static void riscv_host_cpu_init(Object *obj)
     set_misa(env, MXL_RV64, 0);
 #endif
     riscv_cpu_add_user_properties(obj);
+    env->priv_ver = PRIV_VERSION_LATEST;
 }
 #endif
 
@@ -1981,6 +1989,10 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char **isa_str,
     int i;
 
     for (i = 0; i < ARRAY_SIZE(isa_edata_arr); i++) {
+        if (riscv_running_kvm() && !isa_edata_arr[i].kvm_available) {
+            continue;
+        }
+
         if (cpu->env.priv_ver >= isa_edata_arr[i].min_version &&
             isa_ext_is_enabled(cpu, &isa_edata_arr[i])) {
             new = g_strconcat(old, "_", isa_edata_arr[i].name, NULL);
-- 
2.40.1