From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 476694BB28D; Mon, 28 Sep 2026 13:55:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790603719; cv=none; b=LywOb+FqQQB3NWAiGxVTVDdMHYqdpHqM4h/C9CPIy452GilidqJEx3aQ83oCwZPT0/GE4okeVc54oh58/EFZhTvf07lipzlRTf8oayIQqt2EUV5uQAAK4vzsyOYLgGMhP/dRxloYTCl3bLkwdxRRqS8wavHQphkicFWL3k0lqnc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790603719; c=relaxed/simple; bh=lgeeKqhHEm895kCw60vcS0c0qbxLWa1KXH5dC+xZ8o8=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=i+kww8iSKZ+B1FVFxw8Ipqg/3tOxqe0gHMiGCwq/U+HTLreH35LDrSYOO1xojynDGdmzVO/sneoArgY8mNEaE2qRH0GjgZSjH/672XqX4bhvWK+kSHp5H/NM1Wd2dlzQlJoT8rrl9OHNnFGXhBz6ntKrcQKHPXm8yEJlyORbb1I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=RG9oNy0L; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="RG9oNy0L" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3268B1C00; Mon, 28 Sep 2026 06:55:13 -0700 (PDT) Received: from [10.57.12.116] (unknown [10.57.12.116]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 615A83F763; Mon, 28 Sep 2026 06:55:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790603716; bh=lgeeKqhHEm895kCw60vcS0c0qbxLWa1KXH5dC+xZ8o8=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=RG9oNy0LPgTYLRgj8BSKPfl3R2ijszuaO5nA36mQiS+YKA5nXtyqzqZI2lPorQ4+9 1vp9yUr/Qn39ZN9AzUo9KCPbSvxgyi5OAIXa7MmF/pM0iIoUG4EfnZS6hnKZLBEIzP nwsRygXMdeTncPucYonHNNnFZBQqZL2gWkIDK/aY= Message-ID: <195cdfe4-a55a-453f-9c34-620738eca244@arm.com> Date: Mon, 28 Sep 2026 14:55:11 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v19 5/7] firmware: arm_rmm: Activate the RMM Content-Language: en-GB From: Suzuki K Poulose To: Catalin Marinas Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, maz@kernel.org, will@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com, sudeep.holla@arm.com, jonathan.cameron@oss.qualcomm.com References: <20260924135201.850038-1-suzuki.poulose@arm.com> <20260924135201.850038-6-suzuki.poulose@arm.com> <12e83d88-de4c-4230-aac2-1796123320ad@arm.com> <70d47475-e26e-40e1-b409-b0c16aecb8c0@arm.com> In-Reply-To: <70d47475-e26e-40e1-b409-b0c16aecb8c0@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 28/09/2026 10:08, Suzuki K Poulose wrote: > On 25/09/2026 18:50, Suzuki K Poulose wrote: >> Hi Catalin >> >> On 25/09/2026 17:42, Catalin Marinas wrote: >>> On Fri, Sep 25, 2026 at 04:02:24PM +0100, Suzuki K Poulose wrote: >>>> On 25/09/2026 13:17, Catalin Marinas wrote: >>>>> On Thu, Sep 24, 2026 at 02:51:59PM +0100, Suzuki K Poulose wrote: >>>>>> From: Steven Price >>>>>> >>>>>> Activate the RMM after the basic configuration. This is a memory >>>>>> transferring stateful operation. >>>>>> >> >> ... >> >>>>>> + >>>>>> +    ret = rmi_sro_memxfer_cmd(sro, GFP_KERNEL, >>>>>> SMC_RMI_RMM_ACTIVATE); >>>>>> +    if (ret) { >>>>>> +        pr_err("RMM activate failed (%d)\n", ret); >>>>>> +        ret = ret < 0 ? ret : -ENXIO; >>>>>> +    } >>>>>> + >>>>>> +    return ret; >>>>> >>>>> It was raised earlier this year [1] but I'm not sure it concluded. How >>>>> do we handle kexec and kdump? I think RMI_RMM_DEACTIVATE only succeeds >>>>> if nothing is delegated, so it would need all realms torn down >>>>> first. If >>>>> that's not feasible, we could at least block (non-crash) kexec like >>>>> pKVM >>>>> does. >>>> >>>> You are right, we can't DEACTIVATE until all granules have been >>>> "undelegated" back. Not just the Realms, but also the GPTs/Tracking >>>> Metadata etc would need to be reclaimed (when we get to support >>>> dynamic GPT/Tracking metadata). For now, we should block the kexec. >>> >>> Looking more into this (and the memory hotplug story), I find it strange >>> that simply having RME and a valid RMM imposes all these restrictions >>> even if we never run or intend to run a realm. How common will >>> RME-capable systems with RMM firmware be that are not used for CoCo? Or >>> do we expect only CoCo systems to have capable/configured firmware (RME >>> may be present in silicon anyway)? >> >> There is another angle to this : >> >> RMM may act as a TSM (as in the Trusted Security Manager in PCI TDISP) >> context and provide setting up IDE connection between the RootPort/ >> EndPoint. So, the trigger point for the RMM activation would become >> the "First Delegate" request. >> >> Running an RMM just for the "TSM" functionality is not ideal. >> In the absence of RMM, Linux can act as the baremetal TSM. But when the >> RMM is present, we must use the RMM as the TSM, especially if the >> Device will be assigned to a Realm. >> >> FEAT_RME capable systems don't need to enable RMM unless they want to >> run CoCo guests. >> >>> >>> Ideally we'd defer the RMM configuration and activation (and the >>> tracking/GPT checks) until we first attempt to start a realm, keeping >>> only the RMI_VERSION/FEATURES probing at boot. Not sure how feasible >>> this is (memory is more fragmented by then for any contiguous donation). >>> If we manage it, kexec and memory hotplug just work on hosts that never >>> start a realm. >>> >>> The next best thing for kexec is to tear down the realms, undelegate >>> the granules and deactivate the RMM before invoking kexec (with kdump >>> that's harder as we likely no longer have a controlled shutdown). >> >> This is quite complicated, when we get the dynamic metadata support, >> especially with the self-describing L1GPT and Tracking metadata. >> But not impossible. > > Looking at this again we could : > > a. If the user triggers a graceful kexec reboot, i.e, without forced, >    we should be able to deactivate the RMM. Since all processes are >    killed, Realm VMs must be off and all granules reclaimed. >    When we get to dynamic GPT/Tracking, we should additionally >    reclaim them back. > b. For forced reboot kexec, I don't think there is a safe way. > > We have two options here : > > 1. Disable kexec reboot (allowing kexec kdump) when the RMM is active >    at kexec_load. I prefer this for now, and we could goto 2 eventually. > > 2. Back out from machine_kexec() if the RMM was still active. >    This allows (a) above. I have the following patch (tested , but tf-RMM doesn't support DEACTIVATE yet), which correctly deactivates the RMM (well at least tries). ---8>--- firmware: rmm: Deactivate RMM at reboot Deactivate the RMM at system shutdown. This would allow a normal kexec to cleanup the state and boot into a new kernel gracefully. Kdump kernels need not worry about an active RMM, as long as it can handle the GPF on access to the Delegated granules. Signed-off-by: Suzuki K Poulose --- arch/arm64/kernel/machine_kexec.c | 2 + drivers/firmware/arm_rmm/rmi.c | 63 ++++++++++++++++++++++++++++++- include/linux/arm-rmi-cmds.h | 10 +++++ 3 files changed, 73 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index 8f9bc2327dc85..8f16f92a5d389 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c @@ -6,6 +6,7 @@ * Copyright (C) Huawei Futurewei Technologies. */ +#include #include #include #include @@ -171,6 +172,7 @@ void machine_kexec(struct kimage *kimage) BUG_ON(!in_kexec_crash && (stuck_cpus || (num_online_cpus() > 1))); WARN(in_kexec_crash && (stuck_cpus || smp_crash_stop_failed()), "Some CPUs may be stale, kdump will be unreliable.\n"); + WARN(!in_kexec_crash && is_rmm_active(), "RMM is active, kexec will be unreliable.\n"); pr_info("Bye!\n"); diff --git a/drivers/firmware/arm_rmm/rmi.c b/drivers/firmware/arm_rmm/rmi.c index 51343e9d5c2a9..5b695f3155b1c 100644 --- a/drivers/firmware/arm_rmm/rmi.c +++ b/drivers/firmware/arm_rmm/rmi.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include @@ -15,6 +16,13 @@ /* RMM v2.0 defines RmiFeatureRegister0 to RmiFeatureRegister4. */ static unsigned long rmi_feat_reg_cache[5] __ro_after_init; static bool arm64_rmi_is_available; +static bool arm64_rmm_active; + +bool is_rmm_active(void) +{ + return arm64_rmm_active; +} +EXPORT_SYMBOL_GPL(is_rmm_active); /** * rmi_granule_range_undelegate() - Undelegate a range of granules @@ -1017,6 +1025,53 @@ bool is_rmi_available(void) } EXPORT_SYMBOL_GPL(is_rmi_available); +static int rmi_rmm_deactivate(struct rmi_sro_state *sro) +{ + int ret; + + if (!READ_ONCE(arm64_rmm_active)) + return 0; + + ret = WARN_ON(rmi_sro_memxfer_cmd(sro, GFP_KERNEL, SMC_RMI_RMM_DEACTIVATE)); + if (ret) + return ret; + + WRITE_ONCE(arm64_rmm_active, false); + WRITE_ONCE(arm64_rmi_is_available, false); + + return ret; +} + +static int rmi_reboot_notifier(struct notifier_block *nb, + unsigned long action, void *data) +{ + int ret; + + switch (action) { + case SYS_RESTART: + case SYS_HALT: + case SYS_POWER_OFF: + break; + default: + return NOTIFY_DONE; + } + + struct rmi_sro_state *sro __free(kfree) = kmalloc_obj(*sro); + + if (!sro) + return -ENOMEM; + + ret = rmi_rmm_deactivate(sro); + if (ret) + pr_emerg("RMM Deactivation failed: %d\n", ret); + + return NOTIFY_DONE; +} + +static struct notifier_block rmi_reboot_nb = { + .notifier_call = rmi_reboot_notifier, +}; + static int rmi_init_memory(void) { int ret; @@ -1025,7 +1080,10 @@ static int rmi_init_memory(void) if (ret) return ret; - return register_memory_notifier(&rmi_memory_nb); + ret = register_memory_notifier(&rmi_memory_nb); + if (ret) + return ret; + return register_reboot_notifier(&rmi_reboot_nb); } static int __init arm64_init_rmi(void) @@ -1057,10 +1115,11 @@ static int __init arm64_init_rmi(void) return ret; } + WRITE_ONCE(arm64_rmm_active, true); ret = rmi_init_memory(); if (ret) { /* Deactivate the RMM */ - WARN_ON(rmi_sro_memxfer_cmd(sro, GFP_KERNEL, SMC_RMI_RMM_DEACTIVATE)); + (void)rmi_rmm_deactivate(sro); return ret; } diff --git a/include/linux/arm-rmi-cmds.h b/include/linux/arm-rmi-cmds.h index 8fd90914c161a..5d31a4104ce72 100644 --- a/include/linux/arm-rmi-cmds.h +++ b/include/linux/arm-rmi-cmds.h @@ -88,6 +88,16 @@ long rmi_sro_execute(struct arm_smccc_1_2_regs *regs); __ret; \ }) + +#ifdef CONFIG_ARM_RMM_RMI +bool is_rmm_active(void); +#else +static inline bool is_rmm_active(void) +{ + return false; +} +#endif /* CONFIG_ARM_RMM_RMI */ + /** * rmi_rtt_data_map_init() - Create a mapping at protected IPA, copying contents * from a given non-secure source granule. -- 2.43.0