From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44FC2290F for ; Thu, 16 Oct 2025 18:52:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760640776; cv=none; b=nGiVoJvqU7rORLcpy6HwiaBGvsrpWuBBree5BVDt8fjLvhCI2QwixESWH6cb50exJNpK9hhRw8tumFv/dYCLCiYl55AaZGuVxx4/uS8L9rJmHyPosW216/PGY2iO/fe87QB14Cjmm3n0CY5iyPWEP4XzxEpuieAR7LHIPsKpJfk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760640776; c=relaxed/simple; bh=WueHvcKr5EsUw/kTPGTDIhGZhyMzxa3z14GoKAIVh0o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jdsOXhP78pMMLEWG4+fVhkF56w74KswIR1CaZIQPvpqAd6gzygIbYLtpU/ZyTwffk1ifJGDVoXyTw8c+nX5tNCNrGcf57gUoWCKWpt4QFlRy5O85ssQxBCFTluQDB4xRRbwkQ5UafZ0LVaAGHXH4Ooce+Sz1dTiuqj9Nc1hO6og= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=RO5o/lOd; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="RO5o/lOd" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KPO4OMUOafFZ2/AA6OLS6t9Dy0t7EiEKxJlM5HXbLk4=; b=RO5o/lOdn1P1loSyGKNkI0TeHX VwK9O/wZKYoAZoFTs7+31wLT5tUFdecbSCfPiIesbcLcL2DXQFzN6LETONrgXRp1OnHilP+1iBVd+ WvZpzcPcwsZky3YiP+Z9Y2hoDcW0B9RgpUK6sdP6SdjPZQ40DHaZq+Qi9/7DpLN/FmGp2c/MCJ/Iv H6PmO6TqbwlLCkTNj+MlZxtU+Y5OPDnme9WzugbOgp56axjUFbmgUiwaXdKkrCLCeOcypgCSYSzOe wS5bV3GGn+4fOeoHAYQ/b0rXmFPzeqX3p46zeKGCnhQUKT2veMSuQwysDQy9bSTOiL4m4S3GLJ+UU nrqA681w==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1v9T5e-00000006xkD-2rj2; Thu, 16 Oct 2025 18:52:43 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 91864300220; Thu, 16 Oct 2025 20:52:41 +0200 (CEST) Date: Thu, 16 Oct 2025 20:52:41 +0200 From: Peter Zijlstra To: "Kaplan, David" Cc: Thomas Gleixner , Borislav Petkov , Josh Poimboeuf , Pawan Gupta , Ingo Molnar , Dave Hansen , "x86@kernel.org" , "H . Peter Anvin" , Alexander Graf , Boris Ostrovsky , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 40/56] x86/alternative: Use sync_core_nmi_safe() Message-ID: <20251016185241.GG3289052@noisy.programming.kicks-ass.net> References: <20251013143444.3999-1-david.kaplan@amd.com> <20251013143444.3999-41-david.kaplan@amd.com> <20251016103549.GD3289052@noisy.programming.kicks-ass.net> <20251016144730.GC3245006@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Oct 16, 2025 at 03:34:14PM +0000, Kaplan, David wrote: > I will note that on AMD, MFENCE has the required serializing > properties (like SERIALIZE). On AMD, we could use MFENCE in > sync_core() which is probably faster that iret_to_self(). But > again...do we really care. About faster, no. But MFENCE has the benefit of not causing VMEXITs and also not being IRET, so I'm not opposed to you using that as an AMD version of SERIALIZE for the time being.