11.06.2024 06:23, Chuang Xu wrote:
When QEMU is started with:
-cpu host,host-cache-info=on,l3-cache=off \
-smp 2,sockets=1,dies=1,cores=1,threads=2
Guest can't acquire maximum number of addressable IDs for processor cores in
the physical package from CPUID[04H].
When creating a CPU topology of 1 core per package, host-cache-info only
uses the Host's addressable core IDs field (CPUID.04H.EAX[bits 31-26]),
resulting in a conflict (on the multicore Host) between the Guest core
topology information in this field and the Guest's actual cores number.
Fix it by removing the unnecessary condition to cover 1 core per package
case. This is safe because cores_per_pkg will not be 0 and will be at
least 1.
Fixes: d7caf13b5fcf ("x86: cpu: fixup number of addressable IDs for logical
processors sharing cache")
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 | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index bc2dceb647..b68f7460db 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6426,10 +6426,8 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
if (*eax & 31) {
int host_vcpus_per_cache = 1 + ((*eax & 0x3FFC000) >> 14);
- if (cores_per_pkg > 1) {
- *eax &= ~0xFC000000;
- *eax |= max_core_ids_in_package(&topo_info) << 26;
- }
+ *eax &= ~0xFC000000;
+ *eax |= max_core_ids_in_package(&topo_info) << 26;
if (host_vcpus_per_cache > threads_per_pkg) {
*eax &= ~0x3FFC000;
In qemu 9.0, the context is a bit different here:
if (*eax & 31) {
int host_vcpus_per_cache = 1 + ((*eax & 0x3FFC000) >> 14);
int vcpus_per_socket = cs->nr_cores * cs->nr_threads;
if (cs->nr_cores > 1) {
*eax &= ~0xFC000000;
*eax |= (pow2ceil(cs->nr_cores) - 1) << 26;
}
if (host_vcpus_per_cache > vcpus_per_socket) {
Ie, no max_core_ids_in_package(), cores_per_pkg etc, introduced in
v9.0.0-790-gf602eb925a "i386/cpu: Use CPUCacheInfo.share_level to encode
CPUID[4]" and nearby.
Am I right the above change becomes
if (*eax & 31) {
int host_vcpus_per_cache = 1 + ((*eax & 0x3FFC000) >> 14);
int vcpus_per_socket = cs->nr_cores * cs->nr_threads;
- if (cs->nr_cores > 1) {
- *eax &= ~0xFC000000;
- *eax |= (pow2ceil(cs->nr_cores) - 1) << 26;
- }
+ *eax &= ~0xFC000000;
+ *eax |= (pow2ceil(cs->nr_cores) - 1) << 26;
if (host_vcpus_per_cache > vcpus_per_socket) {
*eax &= ~0x3FFC000;
*eax |= (pow2ceil(vcpus_per_socket) - 1) << 14;
in 9.0 -- in other words, just remove the nr_cores condition check
and do the *eax assignment unconditionally ?
From the patch description it seems like it is, but I thought I'd
ask anyway :)
Thanks,
/mjt
--
GPG Key transition (from rsa2048 to rsa4096) since 2024-04-24.
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