Messages in this thread Patch in this message | | | Date | Sun, 14 Sep 2008 10:30:18 +0200 | From | Krzysztof Helt <> | Subject | Re: [PATCH] x86: better CPU identification without the CPUID |
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On Sat, 13 Sep 2008 22:55:10 -0700 "Yinghai Lu" <yhlu.kernel@gmail.com> wrote:
> On Sat, Sep 13, 2008 at 9:43 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote: > > On Sat, Sep 13, 2008 at 3:56 AM, Krzysztof Helt <krzysztof.h1@wp.pl> wrote: > >> From: Krzysztof Helt <krzysztof.h1@wp.pl> > >> > >> cpus without the CPUID instruction are identified > >> as general 386 or 486 while some cpus (mostly made > >> by Cyrix) provide c_identify function which identify > >> correctly older cpus using cpu specific registers). > >> > >> Cyrix cpus are even worse as 5x86 and 6x68 have > >> the CPUID instruction disabled. The CPUID is > >> enabled by the c_identify() but the c_identify > >> is only called when the CPUID is available. > >> > >> Fix this by calling the c_identify() for all known > >> cpu families if there is no the CPUID instruction > > I updated it to tip/master and call that in early_identify_cpu. it > should solve mtrr detection for Cyrix ... >
As I wrote I have no CPU to test this (Cyrix with ARRs). Finally, I am going to buy one or two of them during next two weeks so I will test.
I would like to postpone your patch until I (or someone else) test it.
There is some misunderstanding about the patch. There are two issues here. The early enabling of mtrr registers and nicer and more accurate /proc/cpuinfo content (and the CPU's name during boot). My patch was only about the latter. It was not about the early identification or solving the mtrr problem (as without testing I am not sure I can correctly do this). Your patch resets the /proc/cpuinfo content to the old status (before my patch).
> From: "Yinghai Lu" <yhlu.kernel@gmail.com> > > [PATCH] x86: identify_cpu_without_cpuid > > need to call c_identify() for cpus without cpuid earlier... > > Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
> /* > * Do minimum CPU detection early. > * Fields really needed: vendor, cpuid_level, family, model, mask, > @@ -503,18 +530,17 @@ static void __init early_identify_cpu(st > #endif > c->x86_cache_alignment = c->x86_clflush_size; > > - if (!have_cpuid_p()) > - return; > - > memset(&c->x86_capability, 0, sizeof c->x86_capability); > - > c->extended_cpuid_level = 0; > > - cpu_detect(c); > - > - get_cpu_vendor(c); > - > - get_cpu_cap(c); > + if (!have_cpuid_p()) { > + identify_cpu_without_cpuid(c); > + return; > + } else { > + cpu_detect(c); > + get_cpu_vendor(c); > + get_cpu_cap(c); > + } > > if (this_cpu->c_early_init) > this_cpu->c_early_init(c);
One wants to call c_early_init() here for Cyrix cpus- otherwise the mtrr caps are not set. The correct patch here is only:
- - if (!have_cpuid_p()) - return;
- cpu_detect(c);
+ if (!have_cpuid_p()) + enable_cpuid_on_some_cpus(); /* pseudo code for now */
+ if (have_cpuid_p()) + cpu_detect(c);
The enabling of the cpuid instruction should be added there but only the enabling.
> @@ -583,11 +609,13 @@ static void __cpuinit detect_nopl(struct > > static void __cpuinit generic_identify(struct cpuinfo_x86 *c) > { > - if (!have_cpuid_p()) > - return; > -
I have just checked: http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git
and it differs here. It is the same as in my patch (who is out of sync?).
> @@ -639,17 +667,6 @@ static void __cpuinit identify_cpu(struc > c->x86_cache_alignment = c->x86_clflush_size; > memset(&c->x86_capability, 0, sizeof c->x86_capability); > > - if (!have_cpuid_p()) { > - /* > - * First of all, decide if this is a 486 or higher > - * It's a 486 if we can modify the AC flag > - */ > - if (flag_is_changeable_p(X86_EFLAGS_AC)) > - c->x86 = 4; > - else > - c->x86 = 3; > - } > - > generic_identify(c); > > if (this_cpu->c_identify)
The identify_cpu can stay the way it was. No changes here needed. My patch improves the /proc/cpuinfo content. The next patch should only enable the cpuid instruction on cyrix.
Regards, Krzysztof
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