When QEMU is started with:
-cpu host,migratable=on,host-cache-info=on,l3-cache=off
-smp 180,sockets=2,dies=1,cores=45,threads=2
Try to execute "cpuid -1 -l 1 -r" in guest, we'll obtain a value of 90 for
CPUID.01H.EBX[23:16], while the expected value is 128. And Try to
execute "cpuid -1 -l 4 -r" in guest, we'll obtain a value of 63 for
CPUID.04H.EAX[31:26] as expected.
As (1+CPUID.04H.EAX[31:26]) round up to the nearest power-of-2 integer,
we'd beter round up CPUID.01H.EBX[23:16] to the nearest power-of-2
integer too. Otherwise we may encounter unexpected results in guest.
For example, when QEMU is started with CLI above and xtopology is disabled,
guest kernel 5.15.120 uses CPUID.01H.EBX[23:16]/(1+CPUID.04H.EAX[31:26]) to
calculate threads-per-core in detect_ht(). Then guest will get "90/(1+63)=1"
as the result, even though theads-per-core should actually be 2.
So let us round up CPUID.01H.EBX[23:16] to the nearest power-of-2 integer
to solve the unexpected result.
Signed-off-by: Guixiong Wei <weiguixi...@bytedance.com>
Signed-off-by: Yipeng Yin <yinyip...@bytedance.com>
Signed-off-by: Chuang Xu <xuchuangxc...@bytedance.com>
---
target/i386/cpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 4c2e6f3a71..3710ae5283 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6417,7 +6417,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
}
*edx = env->features[FEAT_1_EDX];
if (threads_per_pkg > 1) {
- *ebx |= threads_per_pkg << 16;
+ *ebx |= pow2ceil(threads_per_pkg) << 16;
*edx |= CPUID_HT;
}
if (!cpu->enable_pmu) {
--
2.20.1
