Rust, target/i386 changes for QEMU 10.1 soft freeze

[PULL 77/77] i386/cpu: Honor maximum value for CPUID.8000001DH.EAX[25:14]

Paolo Bonzini posted 77 patches 4 months ago

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Maintainers: "Philippe Mathieu-Daudé" <philmd@linaro.org>, "Daniel P. Berrangé" <berrange@redhat.com>, Kashyap Chamarthy <kchamart@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Richard Henderson <richard.henderson@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, Cornelia Huck <cohuck@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, Eric Blake <eblake@redhat.com>, Markus Armbruster <armbru@redhat.com>, Manos Pitsidianakis <manos.pitsidianakis@linaro.org>, Zhao Liu <zhao1.liu@intel.com>, Cameron Esfahani <dirty@apple.com>, Roman Bolshakov <rbolshakov@ddn.com>, Phil Dennis-Jordan <phil@philjordan.eu>, Reinoud Zandijk <reinoud@netbsd.org>, Sunil Muthuswamy <sunilmut@microsoft.com>, Warner Losh <imp@bsdimp.com>, Kyle Evans <kevans@freebsd.org>, Ed Maste <emaste@freebsd.org>, Li-Wen Hsu <lwhsu@freebsd.org>, "Alex Bennée" <alex.bennee@linaro.org>, Thomas Huth <thuth@redhat.com>

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[PULL 77/77] i386/cpu: Honor maximum value for CPUID.8000001DH.EAX[25:14]

Posted by Paolo Bonzini 4 months ago

From: Zhao Liu <zhao1.liu@intel.com>

CPUID.8000001DH:EAX[25:14] is "NumSharingCache", and the number of
logical processors sharing this cache is the value of this field
incremented by 1. Because of its width limitation, the maximum value
currently supported is 4095.

Though at present Q35 supports up to 4096 CPUs, by constructing a
specific topology, the width of the APIC ID can be extended beyond 12
bits. For example, using `-smp threads=33,cores=9,modules=9` results in
a die level offset of 6 + 4 + 4 = 14 bits, which can also cause
overflow. Check and honor the maximum value as CPUID.04H did.

Cc: Babu Moger <babu.moger@amd.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250714080859.1960104-8-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 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 fdc677614d8..da7d8dca633 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -560,7 +560,8 @@ static void encode_cache_cpuid8000001d(CPUCacheInfo *cache,
 
     *eax = CACHE_TYPE(cache->type) | CACHE_LEVEL(cache->level) |
                (cache->self_init ? CACHE_SELF_INIT_LEVEL : 0);
-    *eax |= max_thread_ids_for_cache(topo_info, cache->share_level) << 14;
+    /* Bits 25:14 - NumSharingCache: maximum 4095. */
+    *eax |= MIN(max_thread_ids_for_cache(topo_info, cache->share_level), 4095) << 14;
 
     assert(cache->line_size > 0);
     assert(cache->partitions > 0);
-- 
2.50.0