* [PATCH] x86/cpu: remove redundant cpu_detect_cache_sizes
@ 2020-01-15 8:00 Tony W Wang-oc
2020-01-17 18:47 ` Borislav Petkov
2020-01-20 15:39 ` [tip: x86/cpu] x86/cpu: Remove redundant cpu_detect_cache_sizes() call tip-bot2 for Tony W Wang-oc
0 siblings, 2 replies; 4+ messages in thread
From: Tony W Wang-oc @ 2020-01-15 8:00 UTC (permalink / raw)
To: tglx, mingo, bp, hpa, x86, linux-kernel
Cc: DavidWang, CooperYan, QiyuanWang, HerryYang
Before call cpu_detect_cache_sizes get l2size from CPUID.80000006,
these CPUs have called init_intel_cacheinfo get l2size/l3size from
CPUID.4.
So remove the redundant function to simplify the code.
Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
---
arch/x86/kernel/cpu/centaur.c | 2 --
arch/x86/kernel/cpu/zhaoxin.c | 2 --
2 files changed, 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c
index 14433ff..b98529e 100644
--- a/arch/x86/kernel/cpu/centaur.c
+++ b/arch/x86/kernel/cpu/centaur.c
@@ -71,8 +71,6 @@ static void init_c3(struct cpuinfo_x86 *c)
c->x86_cache_alignment = c->x86_clflush_size * 2;
set_cpu_cap(c, X86_FEATURE_REP_GOOD);
}
-
- cpu_detect_cache_sizes(c);
}
enum {
diff --git a/arch/x86/kernel/cpu/zhaoxin.c b/arch/x86/kernel/cpu/zhaoxin.c
index 8e6f2f4..452fd0a 100644
--- a/arch/x86/kernel/cpu/zhaoxin.c
+++ b/arch/x86/kernel/cpu/zhaoxin.c
@@ -58,8 +58,6 @@ static void init_zhaoxin_cap(struct cpuinfo_x86 *c)
if (c->x86 >= 0x6)
set_cpu_cap(c, X86_FEATURE_REP_GOOD);
-
- cpu_detect_cache_sizes(c);
}
static void early_init_zhaoxin(struct cpuinfo_x86 *c)
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] x86/cpu: remove redundant cpu_detect_cache_sizes
2020-01-15 8:00 [PATCH] x86/cpu: remove redundant cpu_detect_cache_sizes Tony W Wang-oc
@ 2020-01-17 18:47 ` Borislav Petkov
2020-01-18 2:18 ` Tony W Wang-oc
2020-01-20 15:39 ` [tip: x86/cpu] x86/cpu: Remove redundant cpu_detect_cache_sizes() call tip-bot2 for Tony W Wang-oc
1 sibling, 1 reply; 4+ messages in thread
From: Borislav Petkov @ 2020-01-17 18:47 UTC (permalink / raw)
To: Tony W Wang-oc
Cc: tglx, mingo, hpa, x86, linux-kernel, DavidWang, CooperYan,
QiyuanWang, HerryYang
On Wed, Jan 15, 2020 at 04:00:57PM +0800, Tony W Wang-oc wrote:
> Before call cpu_detect_cache_sizes get l2size from CPUID.80000006,
> these CPUs have called init_intel_cacheinfo get l2size/l3size from
> CPUID.4.
Questions:
* Does CPUID(4) give the same result as CPUID(80000006) on those CPUs?
* cpu_detect_cache_sizes() sets c->x86_tlbsize while
init_intel_cacheinfo() would set it only when it calls the former
function - cpu_detect_cache_sizes() - at the end:
if (!l2)
cpu_detect_cache_sizes(c);
Does that happen on those CPUs?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86/cpu: remove redundant cpu_detect_cache_sizes
2020-01-17 18:47 ` Borislav Petkov
@ 2020-01-18 2:18 ` Tony W Wang-oc
0 siblings, 0 replies; 4+ messages in thread
From: Tony W Wang-oc @ 2020-01-18 2:18 UTC (permalink / raw)
To: Borislav Petkov
Cc: tglx, mingo, hpa, x86, linux-kernel, DavidWang, CooperYan,
QiyuanWang, HerryYang
On 18/01/2020 02:47, Borislav Petkov wrote:
> On Wed, Jan 15, 2020 at 04:00:57PM +0800, Tony W Wang-oc wrote:
>> Before call cpu_detect_cache_sizes get l2size from CPUID.80000006,
>> these CPUs have called init_intel_cacheinfo get l2size/l3size from
>> CPUID.4.
>
> Questions:
>
> * Does CPUID(4) give the same result as CPUID(80000006) on those CPUs?
Yes.
On these CPUs, CPUID(80000006).EBX for x86_tlbsize is reserved,
CPUID(80000006).ECX for l2size has the same result as CPUID(4).
>
> * cpu_detect_cache_sizes() sets c->x86_tlbsize while
> init_intel_cacheinfo() would set it only when it calls the former
> function - cpu_detect_cache_sizes() - at the end:
>
> if (!l2)
> cpu_detect_cache_sizes(c);
>
> Does that happen on those CPUs?
No.
On these CPUs, will not call the function cpu_detect_cache_sizes(c).
l2size will get from CPUID(4) and c->x86_tlbsize remain its default
value of 0.
Sincerely
TonyWWang-oc
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip: x86/cpu] x86/cpu: Remove redundant cpu_detect_cache_sizes() call
2020-01-15 8:00 [PATCH] x86/cpu: remove redundant cpu_detect_cache_sizes Tony W Wang-oc
2020-01-17 18:47 ` Borislav Petkov
@ 2020-01-20 15:39 ` tip-bot2 for Tony W Wang-oc
1 sibling, 0 replies; 4+ messages in thread
From: tip-bot2 for Tony W Wang-oc @ 2020-01-20 15:39 UTC (permalink / raw)
To: linux-tip-commits; +Cc: Tony W Wang-oc, Borislav Petkov, x86, LKML
The following commit has been merged into the x86/cpu branch of tip:
Commit-ID: 283bab9809786cf41798512f5c1e97f4b679ba96
Gitweb: https://git.kernel.org/tip/283bab9809786cf41798512f5c1e97f4b679ba96
Author: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
AuthorDate: Wed, 15 Jan 2020 16:00:57 +08:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 20 Jan 2020 16:32:35 +01:00
x86/cpu: Remove redundant cpu_detect_cache_sizes() call
Both functions call init_intel_cacheinfo() which computes L2 and L3 cache
sizes from CPUID(4). But then they also call cpu_detect_cache_sizes() a
bit later which computes ->x86_tlbsize and L2 size from CPUID(80000006).
However, the latter call is not needed because
- on these CPUs, CPUID(80000006).EBX for ->x86_tlbsize is reserved
- CPUID(80000006).ECX for the L2 size has the same result as CPUID(4)
Therefore, remove the latter call to simplify the code.
[ bp: Rewrite commit message. ]
Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1579075257-6985-1-git-send-email-TonyWWang-oc@zhaoxin.com
---
arch/x86/kernel/cpu/centaur.c | 2 --
arch/x86/kernel/cpu/zhaoxin.c | 2 --
2 files changed, 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c
index 02d99fe..4267925 100644
--- a/arch/x86/kernel/cpu/centaur.c
+++ b/arch/x86/kernel/cpu/centaur.c
@@ -64,8 +64,6 @@ static void init_c3(struct cpuinfo_x86 *c)
c->x86_cache_alignment = c->x86_clflush_size * 2;
set_cpu_cap(c, X86_FEATURE_REP_GOOD);
}
-
- cpu_detect_cache_sizes(c);
}
enum {
diff --git a/arch/x86/kernel/cpu/zhaoxin.c b/arch/x86/kernel/cpu/zhaoxin.c
index 6b2d3b0..df1358b 100644
--- a/arch/x86/kernel/cpu/zhaoxin.c
+++ b/arch/x86/kernel/cpu/zhaoxin.c
@@ -51,8 +51,6 @@ static void init_zhaoxin_cap(struct cpuinfo_x86 *c)
if (c->x86 >= 0x6)
set_cpu_cap(c, X86_FEATURE_REP_GOOD);
-
- cpu_detect_cache_sizes(c);
}
static void early_init_zhaoxin(struct cpuinfo_x86 *c)
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2020-01-15 8:00 [PATCH] x86/cpu: remove redundant cpu_detect_cache_sizes Tony W Wang-oc
2020-01-17 18:47 ` Borislav Petkov
2020-01-18 2:18 ` Tony W Wang-oc
2020-01-20 15:39 ` [tip: x86/cpu] x86/cpu: Remove redundant cpu_detect_cache_sizes() call tip-bot2 for Tony W Wang-oc
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