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* [PATCH v2 0/6] CPUID and FPU fixes
@ 2017-01-18 19:15 Andy Lutomirski
  2017-01-18 19:15 ` [PATCH v2 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read Andy Lutomirski
  2017-01-18 19:15 ` [PATCH v2 5/6] x86/fpu: Fix CPUID-less FPU detection Andy Lutomirski
  0 siblings, 2 replies; 11+ messages in thread
From: Andy Lutomirski @ 2017-01-18 19:15 UTC (permalink / raw)
  To: X86 ML
  Cc: One Thousand Gnomes, Borislav Petkov, linux-kernel, Brian Gerst,
	Matthew Whitehead, Andy Lutomirski

Our CPUID-less FPU detection code was terminally broken and, as far
as I can tell, it's been broken for a long, long time.  This series
tries to improve the situation.

Changes from v1:
 - Whitespace fixes
 - Prettify the FPU probing code (Borislav)
 - Improve logging (Borislav)

Andy Lutomirski (5):
  x86/cpu: Factor out application of forced cpu caps
  x86/cpu: Re-apply forced caps every time cpu caps are re-read
  x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected" message
  x86/fpu: Fix CPUID-less FPU detection
  x86/fpu: Fix the "Giving up, no FPU found" test

Borislav Petkov (1):
  x86/cpu: Add X86_FEATURE_CPUID

 arch/x86/include/asm/cpufeatures.h |  2 +-
 arch/x86/kernel/cpu/common.c       | 34 +++++++++++++++++++++++-----------
 arch/x86/kernel/fpu/init.c         | 31 +++++++++++++++++--------------
 arch/x86/kernel/fpu/xstate.c       |  8 +++++++-
 4 files changed, 48 insertions(+), 27 deletions(-)

-- 
2.9.3

^ permalink raw reply	[flat|nested] 11+ messages in thread
* [PATCH v2 1/6] x86/cpu: Add X86_FEATURE_CPUID
  2017-01-18 19:15 [PATCH v2 0/6] CPUID and FPU fixes Andy Lutomirski
@ 2017-01-18 19:15 Andy Lutomirski
  2017-01-25 11:40 ` [tip:x86/fpu] " tip-bot for Borislav Petkov
  1 sibling, 1 reply; 11+ messages in thread
From: Andy Lutomirski @ 2017-01-18 19:15 UTC (permalink / raw)
  To: X86 ML
  Cc: One Thousand Gnomes, Borislav Petkov, linux-kernel, Brian Gerst,
	Matthew Whitehead, Borislav Petkov, Andy Lutomirski

From: Borislav Petkov <bp@suse.de>

Add a synthetic CPUID flag denoting whether the CPU sports the CPUID
instruction or not. This will come useful later when accomodating
CPUID-less CPUs.

Signed-off-by: Borislav Petkov <bp@suse.de>
[slightly prettified by Andy]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/cpufeatures.h | 2 +-
 arch/x86/kernel/cpu/common.c       | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 6ccbf1aaa7ce..5108c46e97c4 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -100,7 +100,7 @@
 #define X86_FEATURE_XTOPOLOGY	( 3*32+22) /* cpu topology enum extensions */
 #define X86_FEATURE_TSC_RELIABLE ( 3*32+23) /* TSC is known to be reliable */
 #define X86_FEATURE_NONSTOP_TSC	( 3*32+24) /* TSC does not stop in C states */
-/* free, was #define X86_FEATURE_CLFLUSH_MONITOR ( 3*32+25) * "" clflush reqd with monitor */
+#define X86_FEATURE_CPUID	( 3*32+25) /* CPU has CPUID instruction itself */
 #define X86_FEATURE_EXTD_APICID	( 3*32+26) /* has extended APICID (8 bits) */
 #define X86_FEATURE_AMD_DCM     ( 3*32+27) /* multi-node processor */
 #define X86_FEATURE_APERFMPERF	( 3*32+28) /* APERFMPERF */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 1f6b50a449ab..8f06f7ea4262 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -800,14 +800,12 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 	memset(&c->x86_capability, 0, sizeof c->x86_capability);
 	c->extended_cpuid_level = 0;
 
-	if (!have_cpuid_p())
-		identify_cpu_without_cpuid(c);
-
 	/* cyrix could have cpuid enabled via c_identify()*/
 	if (have_cpuid_p()) {
 		cpu_detect(c);
 		get_cpu_vendor(c);
 		get_cpu_cap(c);
+		setup_force_cpu_cap(X86_FEATURE_CPUID);
 
 		if (this_cpu->c_early_init)
 			this_cpu->c_early_init(c);
@@ -817,6 +815,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
 		if (this_cpu->c_bsp_init)
 			this_cpu->c_bsp_init(c);
+	} else {
+		identify_cpu_without_cpuid(c);
+		setup_clear_cpu_cap(X86_FEATURE_CPUID);
 	}
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
-- 
2.9.3

^ permalink raw reply	[flat|nested] 11+ messages in thread
* [PATCH v2 2/6] x86/cpu: Factor out application of forced cpu caps
  2017-01-18 19:15 [PATCH v2 0/6] CPUID and FPU fixes Andy Lutomirski
@ 2017-01-18 19:15 Andy Lutomirski
  2017-01-25 11:40 ` [tip:x86/fpu] x86/cpu: Factor out application of forced CPU caps tip-bot for Andy Lutomirski
  1 sibling, 1 reply; 11+ messages in thread
From: Andy Lutomirski @ 2017-01-18 19:15 UTC (permalink / raw)
  To: X86 ML
  Cc: One Thousand Gnomes, Borislav Petkov, linux-kernel, Brian Gerst,
	Matthew Whitehead, Andy Lutomirski

There are multiple call sites that apply forced CPU caps.  Factor
them into a helper.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/cpu/common.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8f06f7ea4262..337eac606f39 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -655,6 +655,16 @@ void cpu_detect(struct cpuinfo_x86 *c)
 	}
 }
 
+static void apply_forced_caps(struct cpuinfo_x86 *c)
+{
+	int i;
+
+	for (i = 0; i < NCAPINTS; i++) {
+		c->x86_capability[i] &= ~cpu_caps_cleared[i];
+		c->x86_capability[i] |= cpu_caps_set[i];
+	}
+}
+
 void get_cpu_cap(struct cpuinfo_x86 *c)
 {
 	u32 eax, ebx, ecx, edx;
@@ -1034,10 +1044,7 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 		this_cpu->c_identify(c);
 
 	/* Clear/Set all flags overridden by options, after probe */
-	for (i = 0; i < NCAPINTS; i++) {
-		c->x86_capability[i] &= ~cpu_caps_cleared[i];
-		c->x86_capability[i] |= cpu_caps_set[i];
-	}
+	apply_forced_caps(c);
 
 #ifdef CONFIG_X86_64
 	c->apicid = apic->phys_pkg_id(c->initial_apicid, 0);
@@ -1096,10 +1103,7 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 	 * Clear/Set all flags overridden by options, need do it
 	 * before following smp all cpus cap AND.
 	 */
-	for (i = 0; i < NCAPINTS; i++) {
-		c->x86_capability[i] &= ~cpu_caps_cleared[i];
-		c->x86_capability[i] |= cpu_caps_set[i];
-	}
+	apply_forced_caps(c);
 
 	/*
 	 * On SMP, boot_cpu_data holds the common feature set between
-- 
2.9.3

^ permalink raw reply	[flat|nested] 11+ messages in thread
* [PATCH v2 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected" message
  2017-01-18 19:15 [PATCH v2 0/6] CPUID and FPU fixes Andy Lutomirski
@ 2017-01-18 19:15 Andy Lutomirski
  2017-01-25 11:42 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
  1 sibling, 1 reply; 11+ messages in thread
From: Andy Lutomirski @ 2017-01-18 19:15 UTC (permalink / raw)
  To: X86 ML
  Cc: One Thousand Gnomes, Borislav Petkov, linux-kernel, Brian Gerst,
	Matthew Whitehead, Andy Lutomirski

That message isn't at all clear -- what does "Legacy x87" even
mean?

Clarify it.  If there's no FPU, say "x86/fpu: No FPU detected".  If
there's an FPU that doesn't have XSAVE, say "x86/fpu: x87 FPU will use
FSAVE|FXSAVE".

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/fpu/xstate.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 1d7770447b3e..1691311e5b23 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -705,8 +705,14 @@ void __init fpu__init_system_xstate(void)
 	WARN_ON_FPU(!on_boot_cpu);
 	on_boot_cpu = 0;
 
+	if (!boot_cpu_has(X86_FEATURE_FPU)) {
+		pr_info("x86/fpu: No FPU detected.\n");
+		return;
+	}
+
 	if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
-		pr_info("x86/fpu: Legacy x87 FPU detected.\n");
+		pr_info("x86/fpu: x87 FPU will use %s.\n",
+			boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE");
 		return;
 	}
 
-- 
2.9.3

^ permalink raw reply	[flat|nested] 11+ messages in thread
* [PATCH v2 6/6] x86/fpu: Fix the "Giving up, no FPU found" test
  2017-01-18 19:15 [PATCH v2 0/6] CPUID and FPU fixes Andy Lutomirski
@ 2017-01-18 19:15 Andy Lutomirski
  2017-01-25 11:43 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
  1 sibling, 1 reply; 11+ messages in thread
From: Andy Lutomirski @ 2017-01-18 19:15 UTC (permalink / raw)
  To: X86 ML
  Cc: One Thousand Gnomes, Borislav Petkov, linux-kernel, Brian Gerst,
	Matthew Whitehead, Andy Lutomirski

We would never print "Giving up, no FPU found" because
X86_FEATURE_FPU was in REQUIRED_MASK on non-FPU-emulating builds, so
the boot_cpu_has() test didn't do anything.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/fpu/init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 23601db7b90f..08300d2b9c0f 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -79,7 +79,7 @@ static void fpu__init_system_early_generic(struct cpuinfo_x86 *c)
 	}
 
 #ifndef CONFIG_MATH_EMULATION
-	if (!boot_cpu_has(X86_FEATURE_FPU)) {
+	if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_FPU)) {
 		pr_emerg("x86/fpu: Giving up, no FPU found and no math emulation present\n");
 		for (;;)
 			asm volatile("hlt");
-- 
2.9.3

^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, back to index

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-01-18 19:15 [PATCH v2 0/6] CPUID and FPU fixes Andy Lutomirski
2017-01-18 19:15 ` [PATCH v2 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read Andy Lutomirski
2017-01-19 11:23   ` Borislav Petkov
2017-01-25 11:41   ` [tip:x86/fpu] x86/cpu: Re-apply forced caps every time CPU " tip-bot for Andy Lutomirski
2017-01-18 19:15 ` [PATCH v2 5/6] x86/fpu: Fix CPUID-less FPU detection Andy Lutomirski
2017-01-19 11:23   ` Borislav Petkov
2017-01-25 11:42   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2017-01-18 19:15 [PATCH v2 1/6] x86/cpu: Add X86_FEATURE_CPUID Andy Lutomirski
2017-01-25 11:40 ` [tip:x86/fpu] " tip-bot for Borislav Petkov
2017-01-18 19:15 [PATCH v2 2/6] x86/cpu: Factor out application of forced cpu caps Andy Lutomirski
2017-01-25 11:40 ` [tip:x86/fpu] x86/cpu: Factor out application of forced CPU caps tip-bot for Andy Lutomirski
2017-01-18 19:15 [PATCH v2 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected" message Andy Lutomirski
2017-01-25 11:42 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2017-01-18 19:15 [PATCH v2 6/6] x86/fpu: Fix the "Giving up, no FPU found" test Andy Lutomirski
2017-01-25 11:43 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski

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