linux-kernel - Re: [PATCH 11/16] x86/cpu: Print VMX features as separate line item in /proc/cpuinfo

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Message-ID: <bd2cffea-6427-b3cc-7098-a881e3d4522d@redhat.com>
Date:   Tue, 8 Oct 2019 08:57:30 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Tony W Wang-oc <TonyWWang-oc@...oxin.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-edac@...r.kernel.org,
        Borislav Petkov <bp@...e.de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: Re: [PATCH 11/16] x86/cpu: Print VMX features as separate line item
 in /proc/cpuinfo

On 07/10/19 21:56, Sean Christopherson wrote:
> On Mon, Oct 07, 2019 at 07:12:37PM +0200, Paolo Bonzini wrote:
>> On 04/10/19 23:56, Sean Christopherson wrote:
>>> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
>>> index cb2e49810d68..4eec8889b0ff 100644
>>> --- a/arch/x86/kernel/cpu/proc.c
>>> +++ b/arch/x86/kernel/cpu/proc.c
>>> @@ -7,6 +7,10 @@
>>>  
>>>  #include "cpu.h"
>>>  
>>> +#ifdef CONFIG_X86_VMX_FEATURE_NAMES
>>> +extern const char * const x86_vmx_flags[NVMXINTS*32];
>>> +#endif
>>> +
>>>  /*
>>>   *	Get CPU information for use by the procfs.
>>>   */
>>> @@ -102,6 +106,17 @@ static int show_cpuinfo(struct seq_file *m, void *v)
>>>  		if (cpu_has(c, i) && x86_cap_flags[i] != NULL)
>>>  			seq_printf(m, " %s", x86_cap_flags[i]);
>>
>> I'm afraid this is going to break some scripts in the wild.  I would
>> simply remove the seq_puts below.
> 
> Can you elaborate?  I'm having trouble connecting the dots...

Somebody is bound to have scripts doing "grep ^flags.*ept /proc/cpuinfo"
or checking for VMX flags under some kind of "if (/^flags/)", so it's
safer not to separate VMX and non-VMX flags.

Paolo

>> Paolo
>>
>>> +#ifdef CONFIG_X86_VMX_FEATURE_NAMES
>>> +	if (cpu_has(c, X86_FEATURE_VMX) && c->vmx_capability[0]) {
>>> +		seq_puts(m, "\nvmx flags\t:");
>>> +		for (i = 0; i < 32*NVMXINTS; i++) {
>>> +			if (test_bit(i, (unsigned long *)c->vmx_capability) &&
>>> +			    x86_vmx_flags[i] != NULL)
>>> +				seq_printf(m, " %s", x86_vmx_flags[i]);
>>> +		}
>>> +	}
>>> +#endif
>>> +
>>>  	seq_puts(m, "\nbugs\t\t:");
>>>  	for (i = 0; i < 32*NBUGINTS; i++) {
>>>  		unsigned int bug_bit = 32*NCAPINTS + i;