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Date: Wed, 20 Dec 2017 08:34:56 +1100 From: Benjamin Herrenschmidt <benh@...nel.crashing.org> To: Dave Hansen <dave.hansen@...el.com>, Ram Pai <linuxram@...ibm.com> Cc: mpe@...erman.id.au, mingo@...hat.com, akpm@...ux-foundation.org, corbet@....net, arnd@...db.de, linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org, x86@...nel.org, linux-arch@...r.kernel.org, linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, paulus@...ba.org, khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com, bsingharora@...il.com, hbabu@...ibm.com, mhocko@...nel.org, bauerman@...ux.vnet.ibm.com, ebiederm@...ssion.com Subject: Re: [PATCH v9 29/51] mm/mprotect, powerpc/mm/pkeys, x86/mm/pkeys: Add sysfs interface On Mon, 2017-12-18 at 14:28 -0800, Dave Hansen wrote: > > We do not have generic support for something like that on ppc. > > The kernel looks at the device tree to determine what hardware features > > are available. But does not have mechanism to tell the hardware to track > > which of its features are currently enabled/used by the kernel; atleast > > not for the memory-key feature. > > Bummer. You're missing out. > > But, you could still do this with a syscall. "Hey, kernel, do you > support this feature?" I'm not sure I understand Ram's original (quoted) point, but informing userspace of CPU features is what AT_HWCAP's are about. Ben.
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