From: Thomas Gleixner <tglx@kernel.org>
To: Ryan Roberts <ryan.roberts@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Kees Cook <kees@kernel.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Mark Rutland <mark.rutland@arm.com>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Ard Biesheuvel <ardb@kernel.org>,
Jeremy Linton <jeremy.linton@arm.com>,
David Laight <david.laight.linux@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev,
linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
linux-s390@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v4 3/3] randomize_kstack: Unify random source across arches
Date: Sun, 22 Feb 2026 22:34:26 +0100 [thread overview]
Message-ID: <87ecmcwjh9.ffs@tglx> (raw)
In-Reply-To: <20260119130122.1283821-4-ryan.roberts@arm.com>
On Mon, Jan 19 2026 at 13:01, Ryan Roberts wrote:
> I tested an earlier version of this change on x86 bare metal and it
> showed a smaller but still significant improvement. The bare metal
> system wasn't available this time around so testing was done in a VM
> instance. I'm guessing the cost of rdtsc is higher for VMs.
No it's not, unless the hypervisor traps RDTSC, which would be insane as
that would cause massive regressions all over the place.
So guessing is not really helpful if you want to argue performance.
Thanks,
tglx
next prev parent reply other threads:[~2026-02-22 21:34 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-19 13:01 [PATCH v4 0/3] Fix bugs and performance of kstack offset randomisation Ryan Roberts
2026-01-19 13:01 ` [PATCH v4 1/3] randomize_kstack: Maintain kstack_offset per task Ryan Roberts
2026-01-19 16:10 ` Dave Hansen
2026-01-19 16:51 ` Ryan Roberts
2026-01-19 16:53 ` Dave Hansen
2026-01-19 13:01 ` [PATCH v4 2/3] prandom: Add __always_inline version of prandom_u32_state() Ryan Roberts
2026-01-28 17:00 ` Jason A. Donenfeld
2026-01-28 17:33 ` Ryan Roberts
2026-01-28 18:32 ` David Laight
2026-01-30 16:16 ` Christophe Leroy (CS GROUP)
2026-01-19 13:01 ` [PATCH v4 3/3] randomize_kstack: Unify random source across arches Ryan Roberts
2026-01-20 23:50 ` kernel test robot
2026-01-21 10:20 ` David Laight
2026-01-21 14:48 ` David Laight
2026-01-21 10:52 ` Ryan Roberts
2026-01-21 12:32 ` Mark Rutland
2026-02-18 15:20 ` Ryan Roberts
2026-02-22 21:34 ` Thomas Gleixner [this message]
2026-02-23 9:41 ` David Laight
2026-03-03 14:43 ` Ryan Roberts
2026-01-19 16:00 ` [PATCH v4 0/3] Fix bugs and performance of kstack offset randomisation Dave Hansen
2026-01-19 16:44 ` Kees Cook
2026-01-19 16:51 ` Dave Hansen
2026-01-20 16:32 ` Ryan Roberts
2026-01-20 16:37 ` Dave Hansen
2026-01-20 16:45 ` Ryan Roberts
2026-01-20 18:45 ` David Laight
2026-01-19 16:25 ` Heiko Carstens
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