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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        mingo@redhat.com, bp@alien8.de, dave.hansen@intel.com,
        luto@kernel.org, peterz@infradead.org
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        ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com,
        hpa@zytor.com, jgross@suse.com, jmattson@google.com,
        joro@8bytes.org, jpoimboe@redhat.com, knsathya@kernel.org,
        pbonzini@redhat.com, sdeep@vmware.com, seanjc@google.com,
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        thomas.lendacky@amd.com, brijesh.singh@amd.com, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [PATCHv6 06/30] x86/traps: Refactor exc_general_protection()
In-Reply-To: <20220316020856.24435-7-kirill.shutemov@linux.intel.com>
References: <20220316020856.24435-1-kirill.shutemov@linux.intel.com>
 <20220316020856.24435-7-kirill.shutemov@linux.intel.com>
Date:   Thu, 17 Mar 2022 01:21:53 +0100
Message-ID: <87a6dp2ztq.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, Mar 16 2022 at 05:08, Kirill A. Shutemov wrote:
> TDX brings a new exception -- Virtualization Exception (#VE). Handling
> of #VE structurally very similar to handling #GP.
>
> Extract two helpers from exc_general_protection() that can be reused for
> handling #VE.
>
> No functional changes.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>

Not that I care much, but this is the second instance of something I
suggested. We have tags for that...

> +static bool gp_try_fixup_and_notify(struct pt_regs *regs, int trapnr,
> +				    unsigned long error_code, const char *str)
> +{
> +	int ret;

Adding this to make my suggestion compile is the easy way out, but...

> +
> +	if (fixup_exception(regs, trapnr, error_code, 0))
> +		return true;
> +
> +	current->thread.error_code = error_code;
> +	current->thread.trap_nr = trapnr;
> +
> +	/*
> +	 * To be potentially processing a kprobe fault and to trust the result
> +	 * from kprobe_running(), we have to be non-preemptible.
> +	 */
> +	if (!preemptible() && kprobe_running() &&
> +	    kprobe_fault_handler(regs, trapnr))
> +		return true;
> +
> +	ret = notify_die(DIE_GPF, str, regs, error_code, trapnr, SIGSEGV);
> +	return ret == NOTIFY_STOP;

Why not doing the obvious:

	return notify_die(DIE_GPF, str, regs, error_code, trapnr, SIGSEGV) == NOTIFY_STOP;

Hmm?

Thanks,

        tglx