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Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup
 function
To:     Yu-cheng Yu <yu-cheng.yu@intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@amacapital.net>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
        Dave Martin <Dave.Martin@arm.com>
References: <20190606200926.4029-1-yu-cheng.yu@intel.com>
 <20190606200926.4029-4-yu-cheng.yu@intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
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Message-ID: <c5c21778-f10f-cef8-c937-1e8ad1e2a7cf@intel.com>
Date:   Fri, 7 Jun 2019 12:03:30 -0700
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On 6/6/19 1:09 PM, Yu-cheng Yu wrote:
> +	modify_fpu_regs_begin();
> +	rdmsrl(MSR_IA32_U_CET, r);
> +	r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
> +	wrmsrl(MSR_IA32_U_CET, r);
> +	modify_fpu_regs_end();

Isn't there a bunch of other stuff in this MSR?  It seems like the
bitmap value would allow overwriting lots of bits in the MSR that have
nothing to do with the bitmap... in a prctl() that's supposed to only be
dealing with the bitmap.