From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 79BCCCD98CE for ; Fri, 12 Jun 2026 17:21:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Type:MIME-Version:References:Message-ID:Subject:To:From:Date:Reply-To :Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iBl9dYFaXSXhLmN7gFb0lJdWFnhcbPV5sg9JKMOIpsw=; b=HU83w5vXWDS/Ixdb/ytyICZ0eQ Z3O3UtguF2D548xGHcVTOLu9+J/lwhFxIZTGAbluhmQDQlXEb0qjongAImrvdhQaKwJYko3LJ2p6o if8IMfAH/kSqPx8rYZydBWPvmS1/4iw4VoJ4XA9qmNQiYvHqfbziS85oLo9wHE9xrri2TOrC0/+cC b6ZmPk1jvtyczI/geoTfcbz/4U0pbW9V26/St6mBolUdikCoMNfEkza7rh3wbGkTWT8M2cq/LVUgz Nfky/FjxpZRkHqlFnEeeZ8JH1he5nPFO9yiv3ga34E4FiGDyC5JSyNK8n0SmDZCwevJ5AofsG4l06 n6afDpXw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wY5ZO-0000000BL8o-0xuZ; Fri, 12 Jun 2026 17:21:26 +0000 Received: from mail-qt1-x82b.google.com ([2607:f8b0:4864:20::82b]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wY5ZL-0000000BL8F-2nUN for kexec@lists.infradead.org; Fri, 12 Jun 2026 17:21:24 +0000 Received: by mail-qt1-x82b.google.com with SMTP id d75a77b69052e-516d0db9372so9723081cf.2 for ; Fri, 12 Jun 2026 10:21:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1781284882; x=1781889682; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=iBl9dYFaXSXhLmN7gFb0lJdWFnhcbPV5sg9JKMOIpsw=; b=fT5CLaNdX6zlfb0h4XYJn5RBuLdQ2aWpbrtiXFP6UHsio0F0ZTNXkvIFuWyXdIGvsv mYgbhV+pyt48nWzrEOYGXQmnqe+hBrxabT73r3dR0/7PvT311vtTZ0bgNcG5bpzwoobj lDSeplT5vbG4vnJYtMXHdpAFYeOSlPaUVyCP79/wWYNeEDattptpLXvLlC+ut/DSrsuw Qsq+OqYkOV9k1+By4+YIDfPxrRfnbVkFyMjiMlDE4DjcRoojc2hfkWSmWSlPlXlCK8KY UuBZJrSv1u/Gxq83rkT3Tu46fkqr1Lx8V+KaPlz6Pq0wdi78lPqVOAHWS8HwjtxUvNw8 c4ag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781284882; x=1781889682; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=iBl9dYFaXSXhLmN7gFb0lJdWFnhcbPV5sg9JKMOIpsw=; b=NqGwODhsm/iAUppOpieKdoVnwDP4CWgWRvImcOXWruCPr0ESp4OpSeGOgo3JBS/bat VHVnicpxQtMLdcuxIVto6nwmDWcg7nCDzjbEypjsNnRHhrMREJVKS7WVKCoDD33JUD/o ShaDjmbBTKpZfY4jetx8XmVjNh68QMkH6LL+aH/k7nf0HDvgmJR+UL88lZ20e/Eh0brO 2rOsslzt3WnhhVV/YiVCdRXdSV43rg5BbNiGLRotoQTk2hTneUkF2RuEgpb2Np57TMLU hlk3APPu94TcL11GRnSg4mbKHKPuiH9XIZYeSR949oww4VITcevqwZJnLR8U5Za22hpe YpJA== X-Forwarded-Encrypted: i=1; AFNElJ8HiUO11NPn5lrZNm47Is6o/Cc8tMkpi2lE8ngYO0ZbHpHFjDK1hQ0/KPsk7otLXcuAx19fkg==@lists.infradead.org X-Gm-Message-State: AOJu0YyX62RsmPpvf7rHNpvy32j5pqZnQ0HSutG6z4DPd/Rnxq4Q7bEf lK7yDBbM16gAzROTjEaeN/vYqVyTrTJtvpIrEun9EWuyG+/Yu30rrnu2fx7ofkn0BzMXt2k+0EL y1t/E X-Gm-Gg: Acq92OECebMLrd57oRfOlvwP9HQkwHK6SlG/9DoN4HivyVHQq5O9kBRe9+SR5myePAT cpWTCbATIsaSsMO/rf97qyE9nhkx7TcIoo2LfqU0CXox2ybEpHGLxvZCm2LTU15Y2cZGVyjyD4i MF+zM/EX5B7MEemQrNZ38uj1rMi7vLBiXmulyDdiPRbJbbaGCioIGdFco505dNk/x6nlHRMwKrn ySf7jDjePcI/ZXx4UpERxd7YU3bFdZXRsS31tovHSJeQ5zIOXDI+DklWfUXOqzs4XyJwzt04HZ+ iK4Aw9n4oSpNfa22/qh7q/6QAqJNz1usWHQygOJhwiYKI1ctRRvC8GIMWBffL8iYuMxWpzSfkGD outiCEOIugPLgMf9j8xd0HWj3+De1AB4m3y4ZofbkVl1JW416i4hw8wuQzbWcTS4daxvA9oaUBF iXAL4u0pBQiDFSV779Y+JKFO7yP922RuL+BpETEmffcbo9YjGuOHQ= X-Received: by 2002:a05:622a:9004:b0:516:e10f:b1fa with SMTP id d75a77b69052e-517fe4df40dmr47158011cf.2.1781284882296; Fri, 12 Jun 2026 10:21:22 -0700 (PDT) Received: from plex ([71.181.43.54]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-517fb61eaf4sm26851211cf.4.2026.06.12.10.21.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jun 2026 10:21:21 -0700 (PDT) Date: Fri, 12 Jun 2026 17:21:20 +0000 From: Pasha Tatashin To: Mike Rapoport Subject: Re: [PATCH v2] pstore: add a KHO backend Message-ID: References: <20260605121040.1177072-1-mclapinski@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260612_102123_711240_6A4385D4 X-CRM114-Status: GOOD ( 17.96 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tony Luck , Pasha Tatashin , Michal Clapinski , Kees Cook , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Alexander Graf , Pratyush Yadav Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 06-12 17:42, Mike Rapoport wrote: > Hi, > > On Fri, Jun 05, 2026 at 02:10:40PM +0200, Michal Clapinski wrote: > > Up to this point to preserve late shutdown logs in memory, users had to > > predefine a memory region using ramoops. This commit changes this by > > preserving a buffer using kexec-handover. > > > > pstore_kho supports preserving only 1 dmesg buffer. > > It gets replaced with the new buffer on every kexec, so the user has to > > copy the file out of pstore after every kexec. > > There is no erase() support. > > Sorry I didn't jump at v1. > > pstore does not really need a KHO backend. It can use ram backend with > reserve_mem and reserve_mem can be preserved with KHO already. I just tested it, and it works well, I think it would be fine for Google's requirements: CONFIG_PSTORE=y CONFIG_PSTORE_RAM=y CONFIG_PSTORE_CONSOLE=y With the following parameters: 'reserve_mem=2M:2M:dmesg_buffer ramoops.mem_name=dmesg_buffer ramoops.max_reason=5 ramoops.console_size=2097152 ramoops.record_size=0 ramoops.ftrace_size=0 ramoops.pmsg_size=0' KHO preserves pstore properly. However, we need one patch that would allow for ramoops console to capture the output even when quiet is provided. Pasha From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qt1-f174.google.com (mail-qt1-f174.google.com [209.85.160.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 54B702DF717 for ; Fri, 12 Jun 2026 17:21:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781284884; cv=none; b=mo6UTOwqBiST3kwRV+/GKk9RSDb1oE9/qlAOoBbgx9P6Eak+s0FepDhNcaFdlJZfd9LYW/RXGfVfmV6janox+8DMF7ytajCgwgZRmw8RKpP4AoDVe0HJ7NVV4UhNnbAKh089SaNFQAuhts5Y2mEFAxgpA3PQpdAeBSgNb4Pv8/M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781284884; c=relaxed/simple; bh=P2p8OB9kmn2OxWpM/fBmBDSX3bOOr5v81JgDV3nSjuw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=F0eAIQKQUmm04gS5V2HbvQc49afAH2c99gw5RW0V0qUWoZHXl720dzMM1Q6KQsp9m6YOLv9Shs5xCjGxv2BwIoJEPZHu9uFDEi5CFnOecBWvfZTxRuPtexjf5FOoxGhlownON3mpzUIJlIS+zw8v5RXbWdHX8b5f25UzjvZSEOU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=soleen.com; spf=pass smtp.mailfrom=soleen.com; dkim=pass (2048-bit key) header.d=soleen.com header.i=@soleen.com header.b=Kd2WdOix; arc=none smtp.client-ip=209.85.160.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=soleen.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=soleen.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=soleen.com header.i=@soleen.com header.b="Kd2WdOix" Received: by mail-qt1-f174.google.com with SMTP id d75a77b69052e-5177945a279so12735561cf.0 for ; Fri, 12 Jun 2026 10:21:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1781284882; x=1781889682; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=iBl9dYFaXSXhLmN7gFb0lJdWFnhcbPV5sg9JKMOIpsw=; b=Kd2WdOix5Djgmw1hsGRQqGIjj38lk7oDf2FL6fjR+myeC4rk+8XqEbaGItHqKi4BMS f1/uHeEVIlHJdwa7GcdW/6aHsvU8zAr4HOsJ4NMqPgLXqNT5eygEmIxrqjy9hA86QihM 7wU3WR4tItMxSfPdZw0mcF8gJVBhVIFRaYp8kesK84MsX9WiBW5YcgBmGzTgvG24YMOu XHOrJqxAcLXTTJDaKln4SsIXkNcjcqaSlCop/N0ruNyL3lmv6cztebr2uBr5GYh0n2Ui rLseWPqgr906GzpxVPzXxmME9NPXSVEF3XuNj0F9f2L5wXt0jl+fdId8uzg46mgWW/WP I0ww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781284882; x=1781889682; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=iBl9dYFaXSXhLmN7gFb0lJdWFnhcbPV5sg9JKMOIpsw=; b=V4KxRWRi9+WUM4uFztgz4ew04PkYcM43H+MqW9KPaDjT6m3fTQ88z0/4dAFa9b5KBZ i3+CjT7xZAPyfmucWdtimR34lLeAN7lfV+BT7TNI4m72lMPyvZnJXD3w8txMkZY/e318 7ShMpTOMlJxQsPWya2H+W4sSG/mN5s7m3BE8FAooV8uIeWm2YwUlNddfN3W84LrOIchP yi1RkRWXB4CaD+7WfyNrAEb6mL5kqyAfCWN+92EH/rzQ2J2dnSCxofauDrJizo+1tc8T ie+yT1bCB/XztQ/KYVXU838wfhLempuTiMQmFX4D8OM02DmrWJ/WtHwh07lupiLlCrQC kEnA== X-Forwarded-Encrypted: i=1; AFNElJ/hJim8biw4sm+heAOlZSGOvsiHezZUdyikVUNZAle5WKGaUQj/tJqNDQThYwGNFPujxl22CbvyCEmVNmo=@vger.kernel.org X-Gm-Message-State: AOJu0YzISYbPhvGE/8BemjOJeXyFjsV1siXm7P4gjXj06T2dNNpY1GTK 8AQXf3kOaQVLAngDURj7bL/iu3q0n8SrW25a4uoHd2e6xUusKolhao0c1UUpV+jnAxA= X-Gm-Gg: Acq92OGYPx0zlbkJQo4fVxmwU8gxxBRfCfbLOeHLvBX4Au3cUQJhtjrfbhEh4opLcTw /7NfP+TqISu+f533BjsVSqkqLmmEz7aHbInFPzsrI3WJKa0ueHAwEDIddXxcvaAJqljtFX+TCnu PiSlyua47GhUrynPr6dT0/C2jVoS6Mv2tf3bHzzQJ4yrGOZCfAfYEbaR0GMNRjnLyXOq+qKOfcU gUxhdJ5G0C9Bu/z3OutsG6cyMSG00XlqtN2uBHtKh1SDbmeTqkL9rxTrbAhb+u3bcjylmDOa6N6 /AcBCnZwHJOToSO71FCj+imiIipvFQ5lMZaPXuvv1ymvY6M68LHKY7JwHwCtV+ZXQDmGPGVfndV r+TH2AwgfC2gT5vUsY8MkfjYAnjLMIMLrkYlEOUWuEXgw+JuYUe2mUhOSCWMFj/ni8Ggmj0G6b4 AVtw+JyoRB8APgwO/FG8/YzIIp0Up8ULlDG5Bs0/u1uO0B1BCLaAM= X-Received: by 2002:a05:622a:9004:b0:516:e10f:b1fa with SMTP id d75a77b69052e-517fe4df40dmr47158011cf.2.1781284882296; Fri, 12 Jun 2026 10:21:22 -0700 (PDT) Received: from plex ([71.181.43.54]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-517fb61eaf4sm26851211cf.4.2026.06.12.10.21.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jun 2026 10:21:21 -0700 (PDT) Date: Fri, 12 Jun 2026 17:21:20 +0000 From: Pasha Tatashin To: Mike Rapoport Cc: Michal Clapinski , Kees Cook , Tony Luck , "Guilherme G. Piccoli" , Pasha Tatashin , Pratyush Yadav , Alexander Graf , linux-kernel@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [PATCH v2] pstore: add a KHO backend Message-ID: References: <20260605121040.1177072-1-mclapinski@google.com> Precedence: bulk X-Mailing-List: linux-kernel@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: On 06-12 17:42, Mike Rapoport wrote: > Hi, > > On Fri, Jun 05, 2026 at 02:10:40PM +0200, Michal Clapinski wrote: > > Up to this point to preserve late shutdown logs in memory, users had to > > predefine a memory region using ramoops. This commit changes this by > > preserving a buffer using kexec-handover. > > > > pstore_kho supports preserving only 1 dmesg buffer. > > It gets replaced with the new buffer on every kexec, so the user has to > > copy the file out of pstore after every kexec. > > There is no erase() support. > > Sorry I didn't jump at v1. > > pstore does not really need a KHO backend. It can use ram backend with > reserve_mem and reserve_mem can be preserved with KHO already. I just tested it, and it works well, I think it would be fine for Google's requirements: CONFIG_PSTORE=y CONFIG_PSTORE_RAM=y CONFIG_PSTORE_CONSOLE=y With the following parameters: 'reserve_mem=2M:2M:dmesg_buffer ramoops.mem_name=dmesg_buffer ramoops.max_reason=5 ramoops.console_size=2097152 ramoops.record_size=0 ramoops.ftrace_size=0 ramoops.pmsg_size=0' KHO preserves pstore properly. However, we need one patch that would allow for ramoops console to capture the output even when quiet is provided. Pasha