x86/AMD: make use of CPUID leaf 0xb when available

Initially I did simply stumble across a backport of Linux commit
e0ceeae708 ("x86/CPU/hygon: Fix phys_proc_id calculation logic for
multi-die processors") to our kernels. There I got puzzled by the claim
that a similar change isn't needed on the AMD side. As per the web page
cited [1], there aren't supposed to be affected AMD processors, but
according to my reading there are: The EPYC 7000 series comes with 8,
16, 24, or 32 cores, which I imply to be 1, 2, 3, or 4 die processors.
And many of them have "1P/2P" in the "socket count" column. Therefore
our calculation, being based on CPUID.80000008.EBX[15:12], would be
similarly wrong on such 2-socket 1- or 2-die systems.

Checking Linux code I then found that they don't even rely on the
calculation we currently use anymore, at least not in the case when
leaf 0xb is available (which is the case on Fam17). Let's follow
Suravee's Linux commit 3986a0a805 ("x86/CPU/AMD: Derive CPU topology
from CPUID function 0xB when available") in this regard to address this.

To avoid logging duplicate information, make the function return bool.
Move its and detect_ht()'s declaration to a private header at the same
time.

[1] https://www.amd.com/en/products/specifications/processors

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index 8404cf290fc04dbd2a7d91f6e2bfadb23e96a307..e8be2e6c50d83b1f9ff94fae87d6ed2a62c66d38 100644 (file)
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -515,6 +515,13 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
                         c->cpu_core_id = ebx & 0xFF;
                         c->x86_max_cores /= c->x86_num_siblings;
                 }
+
+                /*
+                 * In case leaf B is available, use it to derive
+                 * topology information.
+                 */
+                if (detect_extended_topology(c))
+                        return;
         }
         
         if (opt_cpu_info)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 4985a4a0ae8d77f1c3263bbe30c0a3804831f519..1db96d959c7aba901c2f3ae6fd093d85ce58e38c 100644 (file)
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -533,7 +533,7 @@ void identify_cpu(struct cpuinfo_x86 *c)
  * Check for extended topology enumeration cpuid leaf 0xb and if it
  * exists, use it for cpu topology detection.
  */
-void detect_extended_topology(struct cpuinfo_x86 *c)
+bool detect_extended_topology(struct cpuinfo_x86 *c)
 {
        unsigned int eax, ebx, ecx, edx, sub_index;
        unsigned int ht_mask_width, core_plus_mask_width;
@@ -541,13 +541,13 @@ void detect_extended_topology(struct cpuinfo_x86 *c)
        unsigned int initial_apicid;
 
        if ( c->cpuid_level < 0xb )
-               return;
+               return false;
 
        cpuid_count(0xb, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
 
        /* Check if the cpuid leaf 0xb is actually implemented */
        if ( ebx == 0 || (LEAFB_SUBTYPE(ecx) != SMT_TYPE) )
-               return;
+               return false;
 
        __set_bit(X86_FEATURE_XTOPOLOGY, c->x86_capability);
 
@@ -588,6 +588,8 @@ void detect_extended_topology(struct cpuinfo_x86 *c)
                        printk("CPU: Processor Core ID: %d\n",
                               c->cpu_core_id);
        }
+
+       return true;
 }
 
 void detect_ht(struct cpuinfo_x86 *c)

diff --git a/xen/arch/x86/cpu/cpu.h b/xen/arch/x86/cpu/cpu.h
index 30cd3a85783cb12e4b59059859ec68686a86f26c..c2f4d9a06ae542e8f64b0919893ec365ec9f0bc8 100644 (file)
--- a/xen/arch/x86/cpu/cpu.h
+++ b/xen/arch/x86/cpu/cpu.h
@@ -15,4 +15,7 @@ extern unsigned int opt_cpuid_mask_ext_ecx, opt_cpuid_mask_ext_edx;
 extern int get_model_name(struct cpuinfo_x86 *c);
 extern void display_cacheinfo(struct cpuinfo_x86 *c);
 
+extern void detect_ht(struct cpuinfo_x86 *c);
+extern bool detect_extended_topology(struct cpuinfo_x86 *c);
+
 void early_init_amd(struct cpuinfo_x86 *c);

diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index cef3ffb8b0ba429b46f295987ed62d275dcce15c..6051b92fdbd8ecea483827433b2800a6c55862f6 100644 (file)
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -170,10 +170,6 @@ extern void setup_force_cpu_cap(unsigned int);
 extern void print_cpu_info(unsigned int cpu);
 extern unsigned int init_intel_cacheinfo(struct cpuinfo_x86 *c);
 
-extern void detect_extended_topology(struct cpuinfo_x86 *c);
-
-extern void detect_ht(struct cpuinfo_x86 *c);
-
 #define cpu_to_core(_cpu)   (cpu_data[_cpu].cpu_core_id)
 #define cpu_to_socket(_cpu) (cpu_data[_cpu].phys_proc_id)