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

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Message-ID: <a6007c5e-a91d-0f4a-7432-aab46bb52763@redhat.com>
Date:   Wed, 9 Oct 2019 23:13:31 +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 09/10/19 21:16, Sean Christopherson wrote:
> On Tue, Oct 08, 2019 at 08:57:30AM +0200, Paolo Bonzini wrote:
>> 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.
> 
> Are the names of the flags considered ABI?  If so, then the rename of
> "vnmi" to "virtual_nmis" also needs to be dropped.  :-(

Yes, they are. :/

Paolo