[PATCH v3 09/10] target/i386: Use AMD legacy cache fallback for Hygon

When legacy-cache=on, x86_cpu_realizefn() builds a hardcoded cache
model.  It selected the AMD legacy cache table only for CPUs with the
AuthenticAMD vendor ID.  Dhyana uses the HygonGenuine vendor ID, so this
explicit compatibility path fell back to QEMU's old Intel legacy cache
table.

The wrong table is visible through AMD extended cache leaves.  With the
Intel legacy table, Dhyana reports 32 KiB, 8-way L1 caches in CPUID
0x80000005 and a 4 MiB, 16-way L2 cache in CPUID 0x80000006.  Linux
uses the AMD/Hygon cache enumeration path for Hygon and reads these AMD
extended cache leaves.

Use the AMD legacy cache table for Hygon in this fallback path when the
new vendor CPU ABI is enabled.  Keep the old fallback for pc-11.1 and
older machine types through x-hygon-vendor-abi-fixes=false.

The default Dhyana model is unchanged because it provides EPYC cache_info
and therefore defaults legacy-cache to off.  The guest-visible change is
limited to users who explicitly configure legacy-cache=on on new machine
types.

Signed-off-by: Tina Zhang <[email protected]>
Reviewed-by: Zhao Liu <[email protected]>
---
 target/i386/cpu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 8666f66df8..f65a5b32bc 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -10329,7 +10329,8 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
             env->enable_legacy_vendor_cache = true;
         }
 
-        if (IS_AMD_CPU(env)) {
+        if (IS_AMD_CPU(env) ||
+            (IS_HYGON_CPU(env) && cpu->hygon_vendor_abi_fixes)) {
             env->cache_info = legacy_amd_cache_info;
         } else {
             env->cache_info = legacy_intel_cache_info;
-- 
2.43.7