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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a53229e014sm13068138f8f.3.2025.06.10.12.53.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Jun 2025 12:54:00 -0700 (PDT) Date: Tue, 10 Jun 2025 20:53:58 +0100 From: David Laight To: Christophe Leroy Cc: Jaroslav Kysela , Takashi Iwai , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sound@vger.kernel.org, Herve Codina , Mark Brown Subject: Re: [PATCH] ALSA: pcm: Convert multiple {get/put}_user to user_access_begin/user_access_end() Message-ID: <20250610205358.07b1cc05@pumpkin> In-Reply-To: References: X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 7 Jun 2025 13:37:42 +0200 Christophe Leroy wrote: > With user access protection (Called SMAP on x86 or KUAP on powerpc) > each and every call to get_user() or put_user() performs heavy > operations to unlock and lock kernel access to userspace. > > To avoid that, perform user accesses by blocks using > user_access_begin/user_access_end() and unsafe_get_user()/ > unsafe_put_user() and alike. Did you consider using masked_user_access_begin() ? It removes a conditional branch and lfence as well. David