Date: Tue, 10 Sep 2013 18:09:54 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Matthew Fleming <mdf@FreeBSD.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r255439 - head/sys/dev/cpuctl Message-ID: <20130910150954.GW41229@kib.kiev.ua> In-Reply-To: <CAMBSHm89omtP=G6eHCHbx%2BXOxHKSgEB4qFBpYvE7=7CAriQfvg@mail.gmail.com> References: <201309100517.r8A5HrHY020358@svn.freebsd.org> <CAMBSHm89omtP=G6eHCHbx%2BXOxHKSgEB4qFBpYvE7=7CAriQfvg@mail.gmail.com>
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--ben6AifVmj+t9BPa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Sep 10, 2013 at 07:29:51AM -0700, Matthew Fleming wrote: > I don't know exactly what the stock malloc(9) will return, but memguard(9= ), > under its default mode with vm.memguard.options having MG_GUARD_AROUND set > will align the returned pointer to only 16 bytes. When I added that > feature I almost made it 8 bytes, but I think I saw that uma(9) had a > 16-byte alignment so I preserved that. I.e., this code does still work > with malloc(9) and memguard(9). >=20 > But why does this need 16 byte alignment? Especially when one of the > comments says 4-byte alignment? The comment about 4-byte alignment is for VIA. For Intel, citing the IA-32 SDM rev. 47, Vol.3, 9.11.6 Microcode Update Loa= der: "The microcode update data requires a 16-byte boundary alignment". I.e. CPU takes the linear address of the buffer, which must be aligned on 16 bytes. --ben6AifVmj+t9BPa Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.21 (FreeBSD) iQIcBAEBAgAGBQJSLzZCAAoJEJDCuSvBvK1ByxcP/RZscqNhXWdzAITJdE9T/6k2 T4nsl05pp29JLRFxOadu/q6aLLLM6ICKvmL4NdFGREw/tuZM63+Fnon2TAQkzZqw JZBF8vRaF2ohtUIL+lXCj6rxCyHMrmwopvTT6NrBTiMeacHd1t6OotERyuDMDjNS mND1QxoDfK/WpHPaf+KMjFz6a7MvXQvz0UF3d3eSqtXBOtDN+35mKdStB2814lJt oOkIgLf9Vy2UYtJ/wUVGyoXs8sVVHtEwjPwGioJ/xruAwzY5w6dkdN3wWSN3WcVe r+DcnHjPpAf7ee7AGcfjSubiU9+rk7Jj1Ft8MXVFlFEVLU0BsQgylHdyxKQrXPe1 S1S4/hEdnJUP23X8Sf+R0KpcKcFRVxRMBUFdTrK3Fkz+s/afSyCYL7OJ+X403S+d 2wFCa5YxzY4hfjffgcE3YCDHvHlYa/LNeTpoV3+oZ6Re55sdMOMW3l6x9URf0qwX 5XtC7+2WtcnSA7t/V+VkbYmEYK6r+zBc61DwzuL31I2GvVyt6/+5jL75nS25zgzR n9jY3ztHMIZEBItwbNn6zqskg9lb8qxAwC8wlPDPYnuPmzSXrc5WqE6Q+AGZEQ6d 2TE+GDNwJHw0SxpFfBq6cbYAakLPKDD1hIOjtvqreLWabr8p9bClvoc7OKO7Gp06 c7TO0taxvkmRr7R6uHkV =8wqz -----END PGP SIGNATURE----- --ben6AifVmj+t9BPa--
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