lkml.org 
[lkml]   [2007]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] rdmsr_on_cpu, wrmsr_on_cpu
Alexey Dobriyan wrote:
> There was OpenVZ specific bug rendering some cpufreq drivers unusable
> on SMP. In short, when cpufreq code thinks it confined itself to
> needed cpu by means of set_cpus_allowed() to execute rdmsr, some
> "virtual cpu" feature can migrate process to anywhere. This triggers
> bugons and does wrong things in general.
>
> This got fixed by introducing rdmsr_on_cpu and wrmsr_on_cpu executing
> rdmsr and wrmsr on given physical cpu by means of
> smp_call_function_single().
>
> Dave Jones mentioned cpufreq might be not only user of rdmsr_on_cpu()
> and wrmsr_on_cpu(), so I'm going to put them into arch/i386/lib/
> (after patch gets some more testing othen than compile and UP run)

The CPUID and MSR drivers need something like this.

HOWEVER -- and this is where things get gnarly -- the CPUID and MSR
drivers would really like to be able to execute CPUID, WRMSR and RDMSR
with the entire GPR register set (except the stack pointer) pre-set and
post-captured, since it's highly likely that there are going to be
nonstandard MSRs and CPUID levels (already witness Intel breaking the
CPUID architecture by introducing %ecx dependencies.)

So I would like to see:

/* It probably makes sense to use the same structure on x86 and
x86-64 */
struct x86_gpr_regs {
u64 rax, rcx, rdx, rbx;
u64 rsp, rbp, rsi, rdi;
u64 r8, r9, r10, r11;
u64 r12, r13, r14, r15;
};

void rdmsr_on_cpu(unsigned cpu,
const struct x86_gpr_regs *in, struct x86_gpr_regs *out);
void wrmsr_on_cpu(unsigned cpu,
const struct x86_gpr_regs *in, struct x86_gpr_regs *out);
void cpuid_on_cpu(unsigned cpu,
const struct x86_gpr_regs *in, struct x86_gpr_regs *out);

This requires assembly to do in the nonparavirtualized case, of course.
I'll try to get that written up in the next day or so.

-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-01-18 23:35    [W:0.066 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site