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Date:   Mon, 23 Oct 2023 12:13:25 -0700
From:   Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To:     Josh Poimboeuf <jpoimboe@kernel.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>, tony.luck@intel.com,
        ak@linux.intel.com, tim.c.chen@linux.intel.com,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        kvm@vger.kernel.org,
        Alyssa Milburn <alyssa.milburn@linux.intel.com>,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        antonio.gomez.iglesias@linux.intel.com,
        Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH  2/6] x86/entry_64: Add VERW just before userspace
 transition
Message-ID: <20231023191325.ot2eomswz4h5aqx2@desk>
References: <20231020-delay-verw-v1-0-cff54096326d@linux.intel.com>
 <20231020-delay-verw-v1-2-cff54096326d@linux.intel.com>
 <20231023182211.5ojm2rsoqqqwqg46@treble>
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On Mon, Oct 23, 2023 at 11:22:11AM -0700, Josh Poimboeuf wrote:
> On Fri, Oct 20, 2023 at 01:45:03PM -0700, Pawan Gupta wrote:
> > +	/* Mitigate CPU data sampling attacks .e.g. MDS */
> > +	USER_CLEAR_CPU_BUFFERS
> > +
> >  	jmp	.Lnative_iret
> >  
> >  
> > @@ -774,6 +780,9 @@ native_irq_return_ldt:
> >  	 */
> >  	popq	%rax				/* Restore user RAX */
> >  
> > +	/* Mitigate CPU data sampling attacks .e.g. MDS */
> > +	USER_CLEAR_CPU_BUFFERS
> > +
> 
> I'm thinking the comments add unnecessary noise here.  The macro name is
> self-documenting enough.
>
> The detail about what mitigations are being done can go above the macro
> definition itself, which the reader can refer to if they want more
> detail about what the macro is doing and why.

Sure, I will move the comments to definition.

> Speaking of the macro name, I think just "CLEAR_CPU_BUFFERS" is
> sufficient.  The "USER_" prefix makes it harder to read IMO.

Ok, will drop "USER_".