linux-kernel - Re: [PATCH 02/30] x86, tlb: make CR4-based TLB flushes more robust

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Date:   Thu, 9 Nov 2017 11:51:08 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
cc:     Dave Hansen <dave.hansen@...ux.intel.com>, luto@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, richard.fellner@...dent.tugraz.at,
        torvalds@...ux-foundation.org, keescook@...gle.com,
        hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 02/30] x86, tlb: make CR4-based TLB flushes more robust

On Thu, 9 Nov 2017, Borislav Petkov wrote:
> On Wed, Nov 08, 2017 at 11:46:49AM -0800, Dave Hansen wrote:
> > +	/* Put original CR4 value back: */
> >  	native_write_cr4(cr4);
> >  }
> 
> Btw, Andy, we read the CR4 shadow in that function but we don't update
> it. Why?

Because its the same as before.

> > +   /* Put original CR4 value back: */
> >     native_write_cr4(cr4);

Thanks,

	tglx