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Donenfeld" , Richard Henderson , linux-alpha@vger.kernel.org, Russell King , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Huacai Chen , loongarch@lists.linux.dev, Geert Uytterhoeven , linux-m68k@lists.linux-m68k.org, Dinh Nguyen , Jonas Bonn , linux-openrisc@vger.kernel.org, Helge Deller , linux-parisc@vger.kernel.org, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Paul Walmsley , linux-riscv@lists.infradead.org, "David S. Miller" , sparclinux@vger.kernel.org Subject: Re: [patch 35/38] s390: Select ARCH_HAS_RANDOM_ENTROPY Message-ID: <20260416134238.9230Ba6-hca@linux.ibm.com> References: <20260410120044.031381086@kernel.org> <20260410120319.924028412@kernel.org> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260410120319.924028412@kernel.org> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE2MDEyNyBTYWx0ZWRfX8JpaMjFpMFNj wT/gcAkcZviN6PAKMrtow2zaUGLfcmRJE1Hmlajk6nmzRCOPN3b0RjfUSbBfZ4kcpBQKzFkFpH2 rBdoNFGP+ENma7o4H4KbJVfdl551lLtrUhXHjq9OwNJzXZ+me9M1v1uiIYgnebcgn173Z5tfoDR wlQdz0La24p7XZm2254oSjajXGSASA40rSmgRE/jrWjf8LX+uVSsnpdh3XNIiRv8V/PTkKj6EBp iBYTVRyCnznRY5uSBKmAQ36JyfUCJkrEoSNgw47/6thxuZYcD3Vho/t2EjbWxo9/yoIVwBhLMiA KDHNz3gXJ52J3z8Lw3ApjdhxznJ9LyQJp5nCQBfITC+W8sZcyql8UU+3NCgtkDEKALiOvDUmzX8 cTJk9dj+/qvxdwTfyZTWoW7vy+HckV57wQs+QYABEOJZttft9F9OCKr+PfGIpmBZixsJntlLk+Y lz3L+7/h8eZbcTrAKmg== X-Proofpoint-ORIG-GUID: rje87_dJEfU9HQ1lSMRsbGj9D9EjeiT6 X-Proofpoint-GUID: mvWCwZrNw9W7TL82vJ98uT3DrwWfuFPP X-Authority-Analysis: v=2.4 cv=fYidDUQF c=1 sm=1 tr=0 ts=69e0e756 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=kj9zAlcOel0A:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=1gfdoSPoDaBUdwTi8XQA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-16_03,2026-04-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 impostorscore=0 clxscore=1011 malwarescore=0 phishscore=0 bulkscore=0 priorityscore=1501 spamscore=0 suspectscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604160127 On Fri, Apr 10, 2026 at 02:21:19PM +0200, Thomas Gleixner wrote: > The only remaining non-architecture usage of get_cycles() is to provide > random_get_entropy(). > > Switch s390 over to the new scheme of selecting ARCH_HAS_RANDOM_ENTROPY and > providing random_get_entropy() in asm/random.h. > > Add 'asm/timex.h' includes to the relevant files, so the global include can > be removed once all architectures are converted over. > > Signed-off-by: Thomas Gleixner > Cc: Heiko Carstens > Cc: linux-s390@vger.kernel.org > --- > arch/s390/Kconfig | 1 + > arch/s390/include/asm/random.h | 12 ++++++++++++ > arch/s390/include/asm/timex.h | 6 ------ > arch/s390/kernel/time.c | 1 + > arch/s390/kernel/vtime.c | 1 + > 5 files changed, 15 insertions(+), 6 deletions(-) Acked-by: Heiko Carstens Thomas, would you mind adding the below as minor improvement to this series? >From 7072e5d66b99a7fa666d17c6ad8cb254f2d8f473 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Thu, 16 Apr 2026 15:08:15 +0200 Subject: [PATCH] s390: Use get_tod_clock_fast() for random_get_entropy() Use get_tod_clock_fast() instead of get_tod_clock_monotonic() to implement random_get_entropy(). There is no need for random_get_entropy() to provide monotonic increasing values, nor is there any need to provide (close to) nanosecond granularity timestamps by shifting the result. This slightly reduces the execution time of random_get_entropy() and adds two bits of randomness. Signed-off-by: Heiko Carstens --- arch/s390/include/asm/random.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/include/asm/random.h b/arch/s390/include/asm/random.h index 7daf42dbed32..f6d9312efdbf 100644 --- a/arch/s390/include/asm/random.h +++ b/arch/s390/include/asm/random.h @@ -6,7 +6,7 @@ static inline unsigned long random_get_entropy(void) { - return (unsigned long)get_tod_clock_monotonic() >> 2; + return get_tod_clock_fast(); } #endif -- 2.51.0