linux-kernel - RE: [PATCH v10 03/38] x86/msr: Add the WRMSRNS instruction support

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Date:   Fri, 22 Sep 2023 17:00:02 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Li, Xin3" <xin3.li@...el.com>, "Li, Xin3" <xin3.li@...el.com>,
        Nikolay Borisov <nik.borisov@...e.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Cc:     "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Gross, Jurgen" <jgross@...e.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "mhiramat@...nel.org" <mhiramat@...nel.org>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
        "jiangshanlai@...il.com" <jiangshanlai@...il.com>
Subject: RE: [PATCH v10 03/38] x86/msr: Add the WRMSRNS instruction support

On Fri, Sep 22 2023 at 08:16, Xin3 Li wrote:
>> > > +static __always_inline void __wrmsrns(u32 msr, u32 low, u32 high)
>> >
>> > Shouldn't this be named wrmsrns_safe since it has exception handling, similar
>> to
>> > the current wrmsrl_safe.
>> >
>> 
>> Both safe and unsafe versions have exception handling, while the safe
>> version returns an integer to its caller to indicate an exception did
>> happen or not.
>
> I notice there are several call sites using the safe version w/o
> checking the return value, should the unsafe version be a better
> choice in such cases?

Depends. The safe version does not emit a warning on fail. So if the
callsite truly does not care about the error it's fine.