From: David Laight <David.Laight@ACULAB.COM>
To: 'Bharata B Rao' <bharata@amd.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"x86@kernel.org" <x86@kernel.org>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"will@kernel.org" <will@kernel.org>,
"shuah@kernel.org" <shuah@kernel.org>,
"oleg@redhat.com" <oleg@redhat.com>,
"ananth.narayan@amd.com" <ananth.narayan@amd.com>
Subject: RE: [RFC PATCH v0 0/6] x86/AMD: Userspace address tagging
Date: Thu, 10 Mar 2022 14:32:46 +0000 [thread overview]
Message-ID: <699fb763ac054833bc8c29c9814c63b2@AcuMS.aculab.com> (raw)
In-Reply-To: <20220310111545.10852-1-bharata@amd.com>
From: Bharata B Rao <bharata@amd.com>
> Sent: 10 March 2022 11:16
>
> This patchset makes use of Upper Address Ignore (UAI) feature available
> on upcoming AMD processors to provide user address tagging support for x86/AMD.
>
> UAI allows software to store a tag in the upper 7 bits of a logical
> address [63:57]. When enabled, the processor will suppress the
> traditional canonical address checks on the addresses. More information
> about UAI can be found in section 5.10 of 'AMD64 Architecture
> Programmer's Manual, Vol 2: System Programming' which is available from
>
> https://bugzilla.kernel.org/attachment.cgi?id=300549
Is that really allowing bit 63 to be used?
That is normally the user-kernel bit.
I can't help feeling that will just badly break things.
Otherwise the best thing is just to change access_ok()
to only reject addresses with the top bit set.
Then you shouldn't need any extra tests in the fast-path
of access_ok().
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-03-10 14:32 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-10 11:15 [RFC PATCH v0 0/6] x86/AMD: Userspace address tagging Bharata B Rao
2022-03-10 11:15 ` [RFC PATCH v0 1/6] mm, arm64: Update PR_SET/GET_TAGGED_ADDR_CTRL interface Bharata B Rao
2022-03-10 11:15 ` [RFC PATCH v0 2/6] x86/cpufeatures: Add Upper Address Ignore(UAI) as CPU feature Bharata B Rao
2022-03-10 11:15 ` [RFC PATCH v0 3/6] x86: Enable Upper Address Ignore(UAI) feature Bharata B Rao
2022-03-10 19:46 ` Andrew Cooper
2022-03-10 22:37 ` David Laight
2022-03-10 22:46 ` Dave Hansen
2022-03-11 12:37 ` Boris Petkov
2022-03-10 11:15 ` [RFC PATCH v0 4/6] x86: Provide an implementation of untagged_addr() Bharata B Rao
2022-03-10 11:15 ` [RFC PATCH v0 5/6] x86: Untag user pointers in access_ok() Bharata B Rao
2022-03-10 11:15 ` [RFC PATCH v0 6/6] x86: Add prctl() options to control tagged user addresses ABI Bharata B Rao
2022-03-10 14:32 ` David Laight [this message]
2022-03-10 16:45 ` [RFC PATCH v0 0/6] x86/AMD: Userspace address tagging Dave Hansen
2022-03-10 17:19 ` David Laight
2022-03-11 5:42 ` Bharata B Rao
2022-03-11 8:15 ` David Laight
2022-03-11 9:11 ` Bharata B Rao
2022-03-11 9:36 ` David Laight
2022-03-11 16:51 ` Dave Hansen
2022-03-10 15:16 ` Dave Hansen
2022-03-10 15:22 ` Dave Hansen
2022-03-14 5:00 ` Bharata B Rao
2022-03-14 7:03 ` Dave Hansen
2022-03-21 22:29 ` Andy Lutomirski
2022-03-21 22:59 ` Thomas Gleixner
2022-03-22 5:31 ` David Laight
2022-03-23 7:48 ` Bharata B Rao
2022-04-01 19:25 ` Dave Hansen
2022-04-05 5:58 ` Bharata B Rao
2022-04-01 19:41 ` Andy Lutomirski
2022-04-05 8:14 ` Peter Zijlstra
2022-04-05 8:40 ` Bharata B Rao
2022-04-08 17:41 ` Catalin Marinas
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