2009-06-09 08:30:00

by Harald Welte

[permalink] [raw]
Subject: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

This patch adds the MSR definitions for the VIA/Centaur CPU models
to cpu_debug.c

Signed-off-by: Harald Welte <[email protected]>
---
arch/x86/include/asm/cpu_debug.h | 21 +++++-
arch/x86/kernel/cpu/cpu_debug.c | 176 ++++++++++++++++++++++++++++++++++++++
2 files changed, 196 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/cpu_debug.h b/arch/x86/include/asm/cpu_debug.h
index 2228020..3790657 100644
--- a/arch/x86/include/asm/cpu_debug.h
+++ b/arch/x86/include/asm/cpu_debug.h
@@ -134,6 +134,12 @@ enum cpu_processor_bit {
CPU_AMD_0F_BIT,
CPU_AMD_10_BIT,
CPU_AMD_11_BIT,
+/* Centaur */
+ CPU_CENTAUR_C3_BIT,
+ CPU_CENTAUR_C5_BIT,
+ CPU_CENTAUR_C7A_BIT,
+ CPU_CENTAUR_C7D_BIT,
+ CPU_CENTAUR_NANO_BIT,
};

#define CPU_INTEL_PENTIUM (1 << CPU_INTEL_PENTIUM_BIT)
@@ -183,8 +189,21 @@ enum cpu_processor_bit {
/* Select all supported AMD CPUs */
#define CPU_AMD_ALL (CPU_AMD_K6 | CPU_K7_PLUS)

+
+#define CPU_CENT_C3 (1 << CPU_CENTAUR_C3_BIT)
+#define CPU_CENT_C5 (1 << CPU_CENTAUR_C5_BIT)
+#define CPU_CENT_C7A (1 << CPU_CENTAUR_C7A_BIT)
+#define CPU_CENT_C7D (1 << CPU_CENTAUR_C7D_BIT)
+#define CPU_CENT_NANO (1 << CPU_CENTAUR_NANO_BIT)
+
+#define CPU_CENT_C7 (CPU_CENT_C7A | CPU_CENT_C7D)
+#define CPU_CENT_C7_PLUS (CPU_CENT_C7 | CPU_CENT_NANO)
+
+#define CPU_CENT_ALL (CPU_CENT_C3 | CPU_CENT_C5 | CPU_CENT_C7 \
+ | CPU_CENT_NANO)
+
/* Select all supported CPUs */
-#define CPU_ALL (CPU_INTEL_ALL | CPU_AMD_ALL)
+#define CPU_ALL (CPU_INTEL_ALL | CPU_AMD_ALL | CPU_CENT_ALL)

#define MAX_CPU_FILES 512

diff --git a/arch/x86/kernel/cpu/cpu_debug.c b/arch/x86/kernel/cpu/cpu_debug.c
index 46e29ab..7add52b 100644
--- a/arch/x86/kernel/cpu/cpu_debug.c
+++ b/arch/x86/kernel/cpu/cpu_debug.c
@@ -2,6 +2,7 @@
* CPU x86 architecture debug code
*
* Copyright(C) 2009 Jaswinder Singh Rajput
+ * Copyright(C) 2009 VIA Technology, Inc.
*
* For licencing details see kernel-base/COPYING
*/
@@ -225,6 +226,93 @@ static struct cpu_debug_range cpu_amd_range[] = {
{ 0xC0011022, 0xC0011023, CPU_CONF, CPU_K10_PLUS, },
};

+/* Centaur Registers Range */
+static struct cpu_debug_range cpu_centaur_range[] = {
+ { 0x00000000, 0x00000001, CPU_MC, CPU_CENT_NANO },
+ { 0x00000006, 0x00000007, CPU_MONITOR, CPU_CENT_NANO },
+ { 0x00000010, 0x00000010, CPU_TIME, CPU_CENT_C7_PLUS },
+ { 0x00000017, 0x00000017, CPU_PLATFORM, CPU_CENT_NANO },
+ { 0x0000001B, 0x0000001B, CPU_APIC, CPU_CENT_C7_PLUS, },
+ { 0x0000002A, 0x0000002A, CPU_POWERON, CPU_CENT_C7_PLUS, },
+ { 0x0000003A, 0x0000003A, CPU_CONTROL, CPU_CENT_NANO, },
+ /* IUA32_BIOS_UDPT_TRIG, trigger bios update */
+ { 0x00000079, 0x00000079, CPU_BIOS, CPU_CENT_NANO, },
+ /* IA32_BIOS_SIGN_ID, determine ucode update level */
+ { 0x0000008B, 0x0000008B, CPU_BIOS, CPU_CENT_NANO, },
+ /* IA32_SMM_MONITOR_CTL */
+ { 0x0000009B, 0x0000009B, CPU_MONITOR, CPU_CENT_NANO, },
+ { 0x000000C1, 0x000000C2, CPU_PMC, CPU_CENT_C7_PLUS, },
+ { 0x000000C3, 0x000000C3, CPU_PMC, CPU_CENT_NANO, },
+ /* MSR_FSB_FREQ */
+ { 0x000000CD, 0x000000CD, CPU_FREQ, CPU_CENT_NANO, },
+ /* IA32_MPERF, IA32_APERF */
+ { 0x000000E7, 0x000000E8, CPU_PERF, CPU_CENT_C7_PLUS, },
+ /* IA32_MTRCAP */
+ { 0x000000FE, 0x000000FE, CPU_MTRR, CPU_CENT_C7_PLUS, },
+ /* MSR_BBL_CR_CTL3 */
+ { 0x0000011E, 0x0000011E, CPU_CACHE, CPU_CENT_C7_PLUS, },
+ /* IA32_SYSENTER_{CS,ESP,EIP} */
+ { 0x00000174, 0x00000176, CPU_SYSENTER, CPU_CENT_C7_PLUS, },
+ { 0x00000186, 0x00000187, CPU_PMC, CPU_CENT_C7_PLUS, },
+ /* performance status, performance control */
+ { 0x00000198, 0x00000199, CPU_PERF, CPU_CENT_C7_PLUS, },
+ /* clock modulation */
+ { 0x0000019A, 0x0000019A, CPU_FREQ, CPU_CENT_C7_PLUS },
+ /* thermal interrupt / status / control */
+ { 0x0000019B, 0x0000019D, CPU_THERM, CPU_CENT_C7_PLUS },
+ /* MISC_Enable, enable TM1/TM2/TM3 */
+ { 0x000001A0, 0x000001A0, CPU_MISC, CPU_CENT_C7_PLUS, },
+ /* IA32_LATFORM_BRV */
+ { 0x000001A1, 0x000001A1, CPU_PLATFORM, CPU_CENT_NANO, },
+ /* IA32_DEBUGCTLA */
+ { 0x000001D9, 0x000001D9, CPU_DEBUG, CPU_CENT_NANO, },
+ { 0x00000200, 0x0000020F, CPU_MTRR, CPU_CENT_C7_PLUS, },
+ { 0x00000250, 0x00000250, CPU_MTRR, CPU_CENT_C7_PLUS, },
+ { 0x00000258, 0x00000259, CPU_MTRR, CPU_CENT_C7_PLUS, },
+ { 0x00000268, 0x0000026F, CPU_MTRR, CPU_CENT_C7_PLUS, },
+ /* IA32_CR_PAT */
+ { 0x00000277, 0x00000277, CPU_PAT, CPU_CENT_NANO, },
+ { 0x000002FF, 0x000002FF, CPU_MTRR, CPU_CENT_C7_PLUS, },
+ { 0x00000309, 0x0000030B, CPU_PMC, CPU_CENT_NANO, },
+ /* IA32_PERF_CAPABILITIES */
+ { 0x00000345, 0x00000345, CPU_PMC, CPU_CENT_NANO, },
+ /* IA32_PERF_{FIXED_CTR_CTRL,GLOBAL_{STATUS,CTRL,OVF_CTRL}} */
+ { 0x0000038D, 0x00000390, CPU_PMC, CPU_CENT_NANO, },
+ /* IA32_PEBS_ENABLE */
+ { 0x000003F1, 0x000003F1, CPU_PMC, CPU_CENT_NANO, },
+ { 0x00000400, 0x00000412, CPU_MC, CPU_CENT_NANO, },
+ { 0x00000480, 0x0000048B, CPU_VMX, CPU_CENT_NANO, },
+ /* FCR5: ucode update status */
+ { 0x00001025, 0x00001025, CPU_BIOS, CPU_CENT_NANO, },
+ { 0x00001107, 0x00001109, CPU_FEATURES, CPU_CENT_C7, },
+ /* Performance Status Register */
+ { 0x0000110A, 0x0000110A, CPU_FEATURES, CPU_CENT_C7D, },
+ { 0x0000110B, 0x0000110B, CPU_MISC, CPU_CENT_C7, },
+ /* HCR2/DSCR2: Overstress VID, Parallax Temp, Inflection ratio */
+ { 0x00001140, 0x00001142, CPU_FREQ, CPU_CENT_C7D, },
+ /* user defined temperature threshuld */
+ { 0x00001167, 0x00001167, CPU_THERM, CPU_CENT_C7, },
+ /* die temperature in degrees C */
+ { 0x00001169, 0x00001169, CPU_THERM, CPU_CENT_C7, },
+ /* CENT_HARDWARECTRL3 */
+ { 0x00001203, 0x00001203, CPU_FEATURES, CPU_CENT_NANO, },
+ /* change reported steppling/model/family */
+ { 0x00001204, 0x00001204, CPU_MISC, CPU_CENT_C7_PLUS, },
+ /* characters of alternate vendor string */
+ { 0x00001206, 0x00001207, CPU_MISC, CPU_CENT_C7_PLUS, },
+ /* CENT_INFLECTION_RATIO */
+ { 0x00001406, 0x00001406, CPU_THERM, CPU_CENT_NANO, },
+ /* thermal monitor temperature in celsius */
+ { 0x00001423, 0x00001423, CPU_THERM, CPU_CENT_NANO, },
+ /* CENT_TMREFCNT{0,1} */
+ { 0x00001424, 0x00001425, CPU_TIME, CPU_CENT_NANO, },
+ /* IA32_EFER */
+ { 0xC0000080, 0xC0000080, CPU_FEATURES, CPU_CENT_NANO, },
+ /* IA32_{STAR,LSTAR,CSTAR,FMASK} */
+ { 0xC0000081, 0xC0000084, CPU_CALL, CPU_CENT_NANO, },
+ /* IA32_{FS_BASE,GS_BASE,KERNEL_GS_BASE} */
+ { 0xC0000100, 0xC0000102, CPU_BASE, CPU_CENT_NANO, },
+};

/* Intel */
static int get_intel_modelflag(unsigned model)
@@ -310,6 +398,77 @@ static int get_amd_modelflag(unsigned model)
return flag;
}

+/* VIA / Centaur */
+static int get_centaur_modelflag(unsigned model)
+{
+ int flag;
+
+ switch ((model >> 8) & 0xff) {
+ case 5:
+ switch (model & 0xff) {
+ case 4:
+ /* IDT WinChip C6 */
+ case 8:
+ /* IDT WinChip 2 */
+ case 9:
+ /* IDT WinChip 3 */
+ default:
+ flag = CPU_NONE;
+ break;
+ }
+ break;
+ case 6:
+ switch (model & 0xff) {
+ case 0x00:
+ /* Cyrix 6x86 MX */
+ flag = CPU_NONE;
+ break;
+ case 0x05:
+ /* VIA Cyrix III */
+ flag = CPU_NONE;
+ break;
+ case 0x06:
+ /* VIA Cyrix III Samuel */
+ flag = CPU_NONE;
+ break;
+ case 0x07:
+ /* 0..7 VIA C3 Samuel II / C3 */
+ /* 8..F VIA C3 Ezra / Eden ESP */
+ flag = CPU_CENT_C3;
+ break;
+ case 0x08:
+ /* 0..7 VIA C3 Ezra-T / Eden ESP */
+ flag = CPU_CENT_C5;
+ break;
+ case 0x09:
+ /* VIA Antaur */
+ flag = CPU_NONE;
+ break;
+ case 0x0a:
+ /* C7-M Type A, Esther core 90nm SOI */
+ flag = CPU_CENT_C7A;
+ break;
+ case 0x0d:
+ /* C7-M Type D, Esther core 90nm */
+ flag = CPU_CENT_C7D;
+ break;
+ case 0x0f:
+ /* Nano 65nm */
+ flag = CPU_CENT_NANO;
+ break;
+ default:
+ flag = CPU_NONE;
+ break;
+ }
+ break;
+ default:
+ flag = CPU_NONE;
+ break;
+ }
+
+ return flag;
+}
+
static int get_cpu_modelflag(unsigned cpu)
{
int flag;
@@ -323,6 +482,9 @@ static int get_cpu_modelflag(unsigned cpu)
case X86_VENDOR_AMD:
flag = get_amd_modelflag(flag & 0xffff);
break;
+ case X86_VENDOR_CENTAUR:
+ flag = get_centaur_modelflag(flag);
+ break;
default:
flag = CPU_NONE;
break;
@@ -342,6 +504,9 @@ static int get_cpu_range_count(unsigned cpu)
case X86_VENDOR_AMD:
index = ARRAY_SIZE(cpu_amd_range);
break;
+ case X86_VENDOR_CENTAUR:
+ index = ARRAY_SIZE(cpu_centaur_range);
+ break;
default:
index = 0;
break;
@@ -375,6 +540,11 @@ static int is_typeflag_valid(unsigned cpu, unsigned flag)
(cpu_amd_range[i].flag & flag))
return 1;
break;
+ case X86_VENDOR_CENTAUR:
+ if ((cpu_centaur_range[i].model & modelflag) &&
+ (cpu_centaur_range[i].flag & flag))
+ return 1;
+ break;
}
}

@@ -404,6 +574,12 @@ static unsigned get_cpu_range(unsigned cpu, unsigned *min, unsigned *max,
*max = cpu_amd_range[index].max;
}
break;
+ case X86_VENDOR_CENTAUR:
+ if ((cpu_centaur_range[index].model & modelflag) &&
+ (cpu_centaur_range[index].flag & flag)) {
+ *min = cpu_centaur_range[index].min;
+ *max = cpu_centaur_range[index].max;
+ }
}

return *max;
--
1.6.3.1


2009-06-09 08:52:43

by Jaswinder Singh Rajput

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

Hello Harald,

On Tue, 2009-06-09 at 16:29 +0800, Harald Welte wrote:
> This patch adds the MSR definitions for the VIA/Centaur CPU models
> to cpu_debug.c
>
> Signed-off-by: Harald Welte <[email protected]>

As per Ingo suggestion, we removed model information from cpu_debug and
is available in -tip :

http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=commitdiff;h=5095f59bda6793a7b8f0856096d6893fe98e0e51

Please check latest -tip from and see how it works with your chips :
git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-tip.git

Currently I am doing more changes and available in :

http://git.kernel.org/?p=linux/kernel/git/jaswinder/linux-2.6-cpu.git;a=shortlog;h=x86/cpu

Thanks,
--
JSR

2009-06-09 15:00:20

by Harald Welte

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

Thanks for your quick response.

On Tue, Jun 09, 2009 at 02:23:18PM +0530, Jaswinder Singh Rajput wrote:

> On Tue, 2009-06-09 at 16:29 +0800, Harald Welte wrote:
> > This patch adds the MSR definitions for the VIA/Centaur CPU models
> > to cpu_debug.c
> >
> > Signed-off-by: Harald Welte <[email protected]>
>
> As per Ingo suggestion, we removed model information from cpu_debug and
> is available in -tip :

but what happens if one MSR has a different group from vendor A to vendor B?
and what happens if you read MSR's on a CPU that doesn't have them? I suppose
you get a segmentation fault, at least that's what I've received in the past
when accidentially reading a MSR that doesn't exist. Is that what the _safe_
variant of rdmsr is for?

> Please check latest -tip from and see how it works with your chips :

I suppose it works, but it probably lacks all the via/centaur specific MSR's.
I'll work on a patch as soon as i find time.

> git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-tip.git
>
> Currently I am doing more changes and available in :
>
> http://git.kernel.org/?p=linux/kernel/git/jaswinder/linux-2.6-cpu.git;a=shortlog;h=x86/cpu

Which means I should base on which of those tree to make sure it can be merged?

--
- Harald Welte <[email protected]> http://linux.via.com.tw/
============================================================================
VIA Free and Open Source Software Liaison

2009-06-09 15:16:17

by Ingo Molnar

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's


* Harald Welte <[email protected]> wrote:

> Thanks for your quick response.
>
> On Tue, Jun 09, 2009 at 02:23:18PM +0530, Jaswinder Singh Rajput wrote:
>
> > On Tue, 2009-06-09 at 16:29 +0800, Harald Welte wrote:
> > > This patch adds the MSR definitions for the VIA/Centaur CPU models
> > > to cpu_debug.c
> > >
> > > Signed-off-by: Harald Welte <[email protected]>
> >
> > As per Ingo suggestion, we removed model information from cpu_debug and
> > is available in -tip :
>
> but what happens if one MSR has a different group from vendor A to
> vendor B? [...]

MSRs should really be enumerated along CPU features. They will be
accessed if a CPU offers that CPU feature.

> [...] and what happens if you read MSR's on a CPU that doesn't
> have them? I suppose you get a segmentation fault, at least
> that's what I've received in the past when accidentially reading a
> MSR that doesn't exist. Is that what the _safe_ variant of rdmsr
> is for?

Yeah, the safe read should never fault - there should be all zeroes
or an error return.

Ingo

2009-06-09 15:18:15

by Jaswinder Singh Rajput

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

On Tue, 2009-06-09 at 22:53 +0800, Harald Welte wrote:
> Thanks for your quick response.
>
> On Tue, Jun 09, 2009 at 02:23:18PM +0530, Jaswinder Singh Rajput wrote:
>
> > On Tue, 2009-06-09 at 16:29 +0800, Harald Welte wrote:
> > > This patch adds the MSR definitions for the VIA/Centaur CPU models
> > > to cpu_debug.c
> > >
> > > Signed-off-by: Harald Welte <[email protected]>
> >
> > As per Ingo suggestion, we removed model information from cpu_debug and
> > is available in -tip :
>
> but what happens if one MSR has a different group from vendor A to vendor B?
> and what happens if you read MSR's on a CPU that doesn't have them? I suppose
> you get a segmentation fault, at least that's what I've received in the past
> when accidentially reading a MSR that doesn't exist. Is that what the _safe_
> variant of rdmsr is for?
>

AFAIK we are using safe variant. That's why I requested you to test
latest -tip and let us know your result and feedback.

> >
> > Currently I am doing more changes and available in :
> >
> > http://git.kernel.org/?p=linux/kernel/git/jaswinder/linux-2.6-cpu.git;a=shortlog;h=x86/cpu
>
> Which means I should base on which of those tree to make sure it can be merged?
>

-tip will be better option.

Thanks,
--
JSR

2009-06-10 04:24:44

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

Ingo Molnar wrote:
>
> MSRs should really be enumerated along CPU features. They will be
> accessed if a CPU offers that CPU feature.
>

Nice in theory, but so many MSRs have to be enumerated with obscure test
combinations, that it really isn't practical in the general case. That
is why we have the safe MSR variants.

>
> Yeah, the safe read should never fault - there should be all zeroes
> or an error return.
>

Error return, MSRs #GP if not present. All zero means a present MSR
(which is zero.)

-hpa

2009-06-10 11:03:00

by Ingo Molnar

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's


* H. Peter Anvin <[email protected]> wrote:

> Ingo Molnar wrote:
> >
> > MSRs should really be enumerated along CPU features. They will be
> > accessed if a CPU offers that CPU feature.
> >
>
> Nice in theory, but so many MSRs have to be enumerated with obscure test
> combinations, that it really isn't practical in the general case. That
> is why we have the safe MSR variants.
>
> >
> > Yeah, the safe read should never fault - there should be all
> > zeroes or an error return.
> >
>
> Error return, MSRs #GP if not present. All zero means a present
> MSR (which is zero.)

yes, of course - i meant the /debug/x86/cpu/* behavior: it should
either result zeroes, or should return -EINVAL. (probably the
latter)

Ingo

2009-06-10 11:11:34

by Michael S. Zick

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

On Wed June 10 2009, Ingo Molnar wrote:
>
> * H. Peter Anvin <[email protected]> wrote:
>
> > Ingo Molnar wrote:
> > >
> > > MSRs should really be enumerated along CPU features. They will be
> > > accessed if a CPU offers that CPU feature.
> > >
> >
> > Nice in theory, but so many MSRs have to be enumerated with obscure test
> > combinations, that it really isn't practical in the general case. That
> > is why we have the safe MSR variants.
> >
> > >
> > > Yeah, the safe read should never fault - there should be all
> > > zeroes or an error return.
> > >
> >
> > Error return, MSRs #GP if not present. All zero means a present
> > MSR (which is zero.)
>
> yes, of course - i meant the /debug/x86/cpu/* behavior: it should
> either result zeroes, or should return -EINVAL. (probably the
> latter)
>

Return zeroes - same as hardware case for bits which can't be set.
Returning -EINVAL might match a specific bit pattern caller is looking for.

Mike
> Ingo
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
>

2009-06-10 11:14:20

by Ingo Molnar

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's


* Michael S. Zick <[email protected]> wrote:

> On Wed June 10 2009, Ingo Molnar wrote:
> >
> > * H. Peter Anvin <[email protected]> wrote:
> >
> > > Ingo Molnar wrote:
> > > >
> > > > MSRs should really be enumerated along CPU features. They will be
> > > > accessed if a CPU offers that CPU feature.
> > > >
> > >
> > > Nice in theory, but so many MSRs have to be enumerated with obscure test
> > > combinations, that it really isn't practical in the general case. That
> > > is why we have the safe MSR variants.
> > >
> > > >
> > > > Yeah, the safe read should never fault - there should be all
> > > > zeroes or an error return.
> > > >
> > >
> > > Error return, MSRs #GP if not present. All zero means a present
> > > MSR (which is zero.)
> >
> > yes, of course - i meant the /debug/x86/cpu/* behavior: it should
> > either result zeroes, or should return -EINVAL. (probably the
> > latter)
> >
>
> Return zeroes - same as hardware case for bits which can't be set.
> Returning -EINVAL might match a specific bit pattern caller is
> looking for.

these files are accessed via read(). The -EINVAL is the syscall
return value. The value (if any) goes into the buffer that is being
read into. So there's no way to 'match a specific bit pattern' -
it's two separate spaces.

Ingo

2009-06-10 11:55:44

by Michael S. Zick

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

On Wed June 10 2009, Ingo Molnar wrote:
>
> * Michael S. Zick <[email protected]> wrote:
>
> > On Wed June 10 2009, Ingo Molnar wrote:
> > >
> > > * H. Peter Anvin <[email protected]> wrote:
> > >
> > > > Ingo Molnar wrote:
> > > > >
> > > > > MSRs should really be enumerated along CPU features. They will be
> > > > > accessed if a CPU offers that CPU feature.
> > > > >
> > > >
> > > > Nice in theory, but so many MSRs have to be enumerated with obscure test
> > > > combinations, that it really isn't practical in the general case. That
> > > > is why we have the safe MSR variants.
> > > >
> > > > >
> > > > > Yeah, the safe read should never fault - there should be all
> > > > > zeroes or an error return.
> > > > >
> > > >
> > > > Error return, MSRs #GP if not present. All zero means a present
> > > > MSR (which is zero.)
> > >
> > > yes, of course - i meant the /debug/x86/cpu/* behavior: it should
> > > either result zeroes, or should return -EINVAL. (probably the
> > > latter)
> > >
> >
> > Return zeroes - same as hardware case for bits which can't be set.
> > Returning -EINVAL might match a specific bit pattern caller is
> > looking for.
>
> these files are accessed via read(). The -EINVAL is the syscall
> return value. The value (if any) goes into the buffer that is being
> read into. So there's no way to 'match a specific bit pattern' -
> it's two separate spaces.
>

Right. Prior post was just a bad case of nerves. ;)

Mike
> Ingo
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
>

2009-06-10 22:31:52

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's

Michael S. Zick wrote:
>> yes, of course - i meant the /debug/x86/cpu/* behavior: it should
>> either result zeroes, or should return -EINVAL. (probably the
>> latter)
>>
>
> Return zeroes - same as hardware case for bits which can't be set.
> Returning -EINVAL might match a specific bit pattern caller is looking for.
>

It should be -EIO anyway, which is what /dev/cpu/*/msr does.

-hpa