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Donenfeld" Subject: Re: [PATCH v2] random: remove CONFIG_ARCH_RANDOM Message-ID: References: <20220706003225.335768-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220706003225.335768-1-Jason@zx2c4.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: jMZP3hl2mP4unmTL5_U5VeAn3puFmrFQ X-Proofpoint-ORIG-GUID: jMZP3hl2mP4unmTL5_U5VeAn3puFmrFQ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-06_04,2022-06-28_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1011 impostorscore=0 mlxlogscore=973 mlxscore=0 suspectscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207060031 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, Arnd Bergmann , Will Deacon , Greg Kroah-Hartman , Catalin Marinas , x86@kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , "H. Peter Anvin" , Alexander Gordeev , linuxppc-dev@lists.ozlabs.org, Thomas Gleixner , linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Jul 06, 2022 at 02:32:25AM +0200, Jason A. Donenfeld wrote: > When RDRAND was introduced, there was much discussion on whether it > should be trusted and how the kernel should handle that. Initially, two > mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and > "nordrand", a boot-time switch. > > Later the thinking evolved. With a properly designed RNG, using RDRAND > values alone won't harm anything, even if the outputs are malicious. > Rather, the issue is whether those values are being *trusted* to be good > or not. And so a new set of options were introduced as the real > ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu". > With these options, RDRAND is used, but it's not always credited. So in > the worst case, it does nothing, and in the best case, maybe it helps. > > Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the > center and became something certain platforms force-select. > > The old options don't really help with much, and it's a bit odd to have > special handling for these instructions when the kernel can deal fine > with the existence or untrusted existence or broken existence or > non-existence of that CPU capability. > > So this commit simplifies things down to the two options that are > actually used, and removes the confusing old ones that aren't used or > useful. It leaves "nordrand" for now, as the removal of that will take a > different route. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Michael Ellerman > Cc: Heiko Carstens > Cc: Alexander Gordeev > Cc: Thomas Gleixner > Cc: H. Peter Anvin > Cc: Greg Kroah-Hartman > Cc: Arnd Bergmann > Signed-off-by: Jason A. Donenfeld ... > arch/s390/Kconfig | 15 --------------- > arch/s390/configs/zfcpdump_defconfig | 1 - > arch/s390/crypto/Makefile | 2 +- > arch/s390/include/asm/archrandom.h | 3 --- For s390: Acked-by: Heiko Carstens