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Mon, 16 Nov 2020 19:45:22 -0800 (PST) From: "Valdis Kl=?utf-8?Q?=c4=93?=tnieks" X-Google-Original-From: "Valdis Kl=?utf-8?Q?=c4=93?=tnieks" X-Mailer: exmh version 2.9.0 11/07/2018 with nmh-1.7+dev To: Wonhyuk Yang Subject: Re: arm64: Question about barriers with the mmu off In-Reply-To: References: <213088.1605579268@turing-police> Mime-Version: 1.0 Date: Mon, 16 Nov 2020 22:45:21 -0500 Message-ID: <218162.1605584721@turing-police> Cc: kernelnewbies X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============7454491052097705264==" Errors-To: kernelnewbies-bounces@kernelnewbies.org --===============7454491052097705264== Content-Type: multipart/signed; boundary="==_Exmh_1605584721_118566P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit --==_Exmh_1605584721_118566P Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Tue, 17 Nov 2020 12:00:32 +0900, Wonhyuk Yang said: > > If you swap them, you get... > > > > dc ivac,x1 // invalidate a cache line that's probably OK > > str w0,=5Bx1 // and now we do a store that leaves a possibly stale = cache line > > > > In other words, if you swap them you may leave an un-invalidated > > stale cache line. > > You mean, even if STCLR_EL1.=7BC, M=7D is cleared, store doesn't bypass= the > cache? That's the problem. The store bypasses the cache line, and the next refe= rence that uses the cache can get stale data. So you have to flush the cache li= ne so the next reference has to refresh the cache on the memory read. --==_Exmh_1605584721_118566P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Comment: Exmh version 2.9.0 11/07/2018 iQIVAwUBX7NHUAdmEQWDXROgAQIaHQ/+PccGu50Rcjahcz75/hVGLHihZh2d4Y3x vXiAyHwDmIdHFjN8UkA+ZmDYJEMNTlFMW+QNsqw2Jl0EC9BYLRRDNHCJ4mpJi7nN wjy0kOCr+gvsCujkM+AMZN94Yic6whjkQDgO15mobKWbAf7C1dKskVLsioqLK/wS +r68fw5MQKZIF0tfZLadp/u0Y583nk0J6ZwKH/uR6++r95osPxIrkNBEHpQ7oSHX DHWUuT7yU3IxSgqFnnxiZxHLMo+mt6OAG01LnmY7UAiZHZv0HQW+ZWK4Oy3UKyyo fe4ToNvwJKd9Kc3L47Au9KFCUnSZ1/+Fipx7lcZ4dzKarURd4i1Wr5+9pwF0qwP8 Tg/IxvLAseNVQV4/sXst1GFXDrRjZbZ5yxGspbkYZxc1/zf23EE8GH1Kz9IE4C7h g/VL/t86ITkXhSZXwD3gGxSTDJtPCJO9zsq61AsicV1d2as3s5X9h1r1yNPq4dc1 axpQygPbx2Mt/nrXyuOjecOR+vjjW0INvgQXHknIYUCsgMh7WwDv0ea3MzRNER1Z kgqytRagcX4kCUBzShuydxqpGJq87VSZpOkFGgXlLsQAmDJ+6TE6hMHpNP3lN15g 913hI8jKQxC4osEiDET1Cx+VPIokg8M+Fc67QLBt/GWD5eqfBY4KpM6muup+4Fem cn7c+043rnI= =z/qP -----END PGP SIGNATURE----- --==_Exmh_1605584721_118566P-- --===============7454491052097705264== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies --===============7454491052097705264==--