Hi Zhao,
在 2023/2/13 17:36, Zhao Liu 写道:
From: Zhao Liu <zhao1....@intel.com>
For i-cache and d-cache, the maximum IDs for CPUs sharing cache (
CPUID.04H.00H:EAX[bits 25:14] and CPUID.04H.01H:EAX[bits 25:14]) are
both 0, and this means i-cache and d-cache are shared in the SMT level.
This is correct if there's single thread per core, but is wrong for the
hyper threading case (one core contains multiple threads) since the
i-cache and d-cache are shared in the core level other than SMT level.
Therefore, in order to be compatible with both multi-threaded and
single-threaded situations, we should set i-cache and d-cache be shared
at the core level by default.
Refer to the fixes of cache_info_passthrough ([1], [2]) and SDM, the
CPUID.04H:EAX[bits 25:14] and CPUID.04H:EAX[bits 31:26] should use the
nearest power-of-2 integer.
The nearest power-of-2 integer can be caculated by pow2ceil() or by
using APIC ID offset (like L3 topology using 1 << die_offset [3]).
But in fact, CPUID.04H:EAX[bits 25:14] and CPUID.04H:EAX[bits 31:26]
are associated with APIC ID. For example, in linux kernel, the field
"num_threads_sharing" (Bits 25 - 14) is parsed with APIC ID. And for
another example, on Alder Lake P, the CPUID.04H:EAX[bits 31:26] is not
matched with actual core numbers and it's caculated by:
"(1 << (pkg_offset - core_offset)) - 1".
Therefore the offset of APIC ID should be preferred to caculate nearest
power-of-2 integer for CPUID.04H:EAX[bits 25:14] and CPUID.04H:EAX[bits
31:26]:
1. d/i cache is shared in a core, 1 << core_offset should be used
instand of "1" in encode_cache_cpuid4() for CPUID.04H.00H:EAX[bits
25:14] and CPUID.04H.01H:EAX[bits 25:14].
2. L2 cache is supposed to be shared in a core as for now, thereby
1 << core_offset should also be used instand of "cs->nr_threads" in
encode_cache_cpuid4() for CPUID.04H.02H:EAX[bits 25:14].
3. Similarly, the value for CPUID.04H:EAX[bits 31:26] should also be
replaced by the offsets upper SMT level in APIC ID.
And since [1] and [2] are good enough to make cache_into_passthrough
work well, its "pow2ceil()" uses are enough so that they're no need to
be replaced by APIC ID offset way.
If you uniformly tweak these two places with APIC ID offset too, then
you can also use the more spec-compliant helpers
(e.g max_processor_ids_for_cache and max_core_ids_in_pkg) here in
future patch #18. Would be it best to uniform the code?
Thanks,
Yanan
[1]: efb3934 (x86: cpu: make sure number of addressable IDs for processor cores
meets the spec)
[2]: d7caf13 (x86: cpu: fixup number of addressable IDs for logical processors
sharing cache)
[3]: d65af28 (i386: Update new x86_apicid parsing rules with die_offset support)
Fixes: 7e3482f (i386: Helpers to encode cache information consistently)
Suggested-by: Robert Hoo <robert...@linux.intel.com>
Signed-off-by: Zhao Liu <zhao1....@intel.com>
---
target/i386/cpu.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 29afec12c281..7833505092d8 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5212,7 +5212,6 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
{
X86CPU *cpu = env_archcpu(env);
CPUState *cs = env_cpu(env);
- uint32_t die_offset;
uint32_t limit;
uint32_t signature[3];
X86CPUTopoInfo topo_info;
@@ -5308,27 +5307,38 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
*eax = *ebx = *ecx = *edx = 0;
} else {
*eax = 0;
+ int addressable_cores_offset = apicid_pkg_offset(&topo_info) -
+ apicid_core_offset(&topo_info);
+ int core_offset, die_offset;
+
switch (count) {
case 0: /* L1 dcache info */
+ core_offset = apicid_core_offset(&topo_info);
encode_cache_cpuid4(env->cache_info_cpuid4.l1d_cache,
- 1, cs->nr_cores,
+ (1 << core_offset),
+ (1 << addressable_cores_offset),
eax, ebx, ecx, edx);
break;
case 1: /* L1 icache info */
+ core_offset = apicid_core_offset(&topo_info);
encode_cache_cpuid4(env->cache_info_cpuid4.l1i_cache,
- 1, cs->nr_cores,
+ (1 << core_offset),
+ (1 << addressable_cores_offset),
eax, ebx, ecx, edx);
break;
case 2: /* L2 cache info */
+ core_offset = apicid_core_offset(&topo_info);
encode_cache_cpuid4(env->cache_info_cpuid4.l2_cache,
- cs->nr_threads, cs->nr_cores,
+ (1 << core_offset),
+ (1 << addressable_cores_offset),
eax, ebx, ecx, edx);
break;
case 3: /* L3 cache info */
die_offset = apicid_die_offset(&topo_info);
if (cpu->enable_l3_cache) {
encode_cache_cpuid4(env->cache_info_cpuid4.l3_cache,
- (1 << die_offset), cs->nr_cores,
+ (1 << die_offset),
+ (1 << addressable_cores_offset),
eax, ebx, ecx, edx);
break;
}
