From: Suzuki K Poulose <suzuki.poulose@arm•com>
To: Marc Zyngier <maz@kernel•org>, Steven Price <steven.price@arm•com>
Cc: kvm@vger•kernel.org, kvmarm@lists•linux.dev,
Catalin Marinas <catalin.marinas@arm•com>,
Will Deacon <will@kernel•org>, James Morse <james.morse@arm•com>,
Oliver Upton <oliver.upton@linux•dev>,
Zenghui Yu <yuzenghui@huawei•com>,
linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, Joey Gouly <joey.gouly@arm•com>,
Alexandru Elisei <alexandru.elisei@arm•com>,
Christoffer Dall <christoffer.dall@arm•com>,
Fuad Tabba <tabba@google•com>,
linux-coco@lists•linux.dev,
Ganapatrao Kulkarni <gankulkarni@os•amperecomputing.com>,
Gavin Shan <gshan@redhat•com>,
Shanker Donthineni <sdonthineni@nvidia•com>,
Alper Gun <alpergun@google•com>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel•org>,
Emi Kisanuki <fj0570is@fujitsu•com>,
Vishal Annapurve <vannapurve@google•com>,
WeiLin.Chang@arm•com, Lorenzo.Pieralisi2@arm•com
Subject: Re: [PATCH v14 09/44] arm64: RMI: Provide functions to delegate/undelegate ranges of memory
Date: Thu, 21 May 2026 17:01:37 +0100 [thread overview]
Message-ID: <a81c3688-30f1-43e4-8d57-1d08a6e563af@arm.com> (raw)
In-Reply-To: <867bowx3qx.wl-maz@kernel.org>
On 21/05/2026 14:59, Marc Zyngier wrote:
> On Wed, 13 May 2026 14:17:17 +0100,
> Steven Price <steven.price@arm•com> wrote:
>>
>> The RMM requires memory is 'delegated' to it so that it can be used
>> either for a realm guest or for various tracking purposes within the RMM
>> (e.g. for metadata or page tables). Memory that has been delegated
>> cannot be accessed by the host (it will result in a Granule Protection
>> Fault).
>>
>> Undelegation may fail if the memory is still in use by the RMM. This
>> shouldn't happen (Linux should ensure it has destroyed the RMM objects
>> before attempting to undelegate). In the event that it does happen this
>> points to a programming bug and the only reasonable approach is for the
>> physical pages to be leaked - it is up to the caller of
>> rmi_undelegate_range() to handle this.
>>
>> Signed-off-by: Steven Price <steven.price@arm•com>
>> ---
>> v14:
>> * Split into separate patch and moved out of KVM
>> ---
>> arch/arm64/include/asm/rmi_cmds.h | 13 +++++++++++
>> arch/arm64/kernel/rmi.c | 36 +++++++++++++++++++++++++++++++
>> 2 files changed, 49 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/rmi_cmds.h b/arch/arm64/include/asm/rmi_cmds.h
>> index 9078a2920a7c..eb213c8e6f26 100644
>> --- a/arch/arm64/include/asm/rmi_cmds.h
>> +++ b/arch/arm64/include/asm/rmi_cmds.h
>> @@ -33,6 +33,19 @@ struct rmi_sro_state {
>> } while (RMI_RETURN_STATUS(res.a0) == RMI_BUSY || \
>> RMI_RETURN_STATUS(res.a0) == RMI_BLOCKED)
>>
>> +int rmi_delegate_range(phys_addr_t phys, unsigned long size);
>> +int rmi_undelegate_range(phys_addr_t phys, unsigned long size);
>> +
>> +static inline int rmi_delegate_page(phys_addr_t phys)
>> +{
>> + return rmi_delegate_range(phys, PAGE_SIZE);
>> +}
>> +
>> +static inline int rmi_undelegate_page(phys_addr_t phys)
>> +{
>> + return rmi_undelegate_range(phys, PAGE_SIZE);
>> +}
>> +
>> bool rmi_is_available(void);
>>
>> unsigned long rmi_sro_execute(struct rmi_sro_state *sro, gfp_t gfp);
>> diff --git a/arch/arm64/kernel/rmi.c b/arch/arm64/kernel/rmi.c
>> index 52a415e99500..08cef54acadb 100644
>> --- a/arch/arm64/kernel/rmi.c
>> +++ b/arch/arm64/kernel/rmi.c
>> @@ -12,6 +12,42 @@ static bool arm64_rmi_is_available;
>> unsigned long rmm_feat_reg0;
>> unsigned long rmm_feat_reg1;
>>
>> +int rmi_delegate_range(phys_addr_t phys, unsigned long size)
>> +{
>> + unsigned long ret = 0;
>> + unsigned long top = phys + size;
>> + unsigned long out_top;
>> +
>> + while (phys < top) {
>> + ret = rmi_granule_range_delegate(phys, top, &out_top);
>> + if (ret == RMI_SUCCESS)
>> + phys = out_top;
>> + else if (ret != RMI_BUSY && ret != RMI_BLOCKED)
>> + return ret;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +int rmi_undelegate_range(phys_addr_t phys, unsigned long size)
>> +{
>> + unsigned long ret = 0;
>> + unsigned long top = phys + size;
>> + unsigned long out_top;
>> +
>> + WARN_ON(size == 0);
>
> I find it odd to warn on size = 0. After all, free(NULL) is not an
> error. But even then, you continue feeding this to the RMM.
>
> You also don't seem to be bothered with that on the delegation side...
>
>> +
>> + while (phys < top) {
>> + ret = rmi_granule_range_undelegate(phys, top, &out_top);
>> + if (ret == RMI_SUCCESS)
>> + phys = out_top;
>
> and size==0 doesn't violate any of the failure conditions listed in
> B4.5.18.2 (beta2). Will you end-up looping around forever?
That is not true ? It triggers, top_bound error condition, for both.
pre: UInt(top) <= UInt(base)
post: result.status == RMI_ERROR_INPUT
Suzuki
>
> Same questions for the delegation, obviously.
>
> M.
>
next prev parent reply other threads:[~2026-05-21 16:01 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-13 13:17 [PATCH v14 00/44] arm64: Support for Arm CCA in KVM Steven Price
2026-05-13 13:17 ` [PATCH v14 01/44] kvm: arm64: Include kvm_emulate.h in kvm/arm_psci.h Steven Price
2026-05-21 10:19 ` Marc Zyngier
2026-05-21 15:11 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 02/44] kvm: arm64: Avoid including linux/kvm_host.h in kvm_pgtable.h Steven Price
2026-05-21 10:26 ` Marc Zyngier
2026-05-21 15:11 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 03/44] arm64: RME: Handle Granule Protection Faults (GPFs) Steven Price
2026-05-21 12:25 ` Marc Zyngier
2026-05-21 15:15 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 04/44] arm64: RMI: Add SMC definitions for calling the RMM Steven Price
2026-05-18 7:08 ` Gavin Shan
2026-05-20 16:01 ` Steven Price
2026-05-21 12:40 ` Marc Zyngier
2026-05-21 14:50 ` Suzuki K Poulose
2026-05-21 15:33 ` Steven Price
2026-05-22 9:58 ` Marc Zyngier
2026-06-03 10:15 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 05/44] arm64: RMI: Add wrappers for RMI calls Steven Price
2026-05-19 5:35 ` Aneesh Kumar K.V
2026-05-21 15:44 ` Steven Price
2026-05-21 0:21 ` Gavin Shan
2026-05-21 15:44 ` Steven Price
2026-05-21 12:49 ` Marc Zyngier
2026-05-21 15:44 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 06/44] arm64: RMI: Check for RMI support at init Steven Price
2026-05-21 0:39 ` Gavin Shan
2026-05-21 15:49 ` Steven Price
2026-05-25 6:58 ` Gavin Shan
2026-06-03 10:57 ` Steven Price
2026-05-21 13:02 ` Marc Zyngier
2026-06-03 10:57 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 07/44] arm64: RMI: Configure the RMM with the host's page size Steven Price
2026-05-21 0:51 ` Gavin Shan
2026-05-21 22:36 ` Suzuki K Poulose
2026-05-21 13:30 ` Marc Zyngier
2026-05-21 14:53 ` Suzuki K Poulose
2026-06-03 15:48 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 08/44] arm64: RMI: Ensure that the RMM has GPT entries for memory Steven Price
2026-05-19 5:55 ` Aneesh Kumar K.V
2026-06-03 15:48 ` Steven Price
2026-05-21 0:58 ` Gavin Shan
2026-06-03 15:48 ` Steven Price
2026-05-21 13:47 ` Marc Zyngier
2026-05-21 14:24 ` Marc Zyngier
2026-05-21 15:39 ` Suzuki K Poulose
2026-06-03 15:48 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 09/44] arm64: RMI: Provide functions to delegate/undelegate ranges of memory Steven Price
2026-05-21 13:59 ` Marc Zyngier
2026-05-21 16:01 ` Suzuki K Poulose [this message]
2026-05-22 10:02 ` Marc Zyngier
2026-06-04 14:43 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 10/44] arm64: RMI: Add support for SRO Steven Price
2026-05-14 8:01 ` Aneesh Kumar K.V
2026-05-14 9:33 ` Steven Price
2026-05-19 6:02 ` Aneesh Kumar K.V
2026-06-04 15:19 ` Steven Price
2026-05-21 4:38 ` Gavin Shan
2026-06-04 15:19 ` Steven Price
2026-05-21 14:35 ` Marc Zyngier
2026-06-04 15:19 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 11/44] arm64: RMI: Check for RMI support at KVM init Steven Price
2026-05-13 13:17 ` [PATCH v14 12/44] arm64: RMI: Check for LPA2 support Steven Price
2026-05-13 13:17 ` [PATCH v14 13/44] arm64: RMI: Define the user ABI Steven Price
2026-05-26 22:17 ` Wei-Lin Chang
2026-06-04 15:27 ` Steven Price
2026-05-27 15:21 ` Marc Zyngier
2026-06-02 11:15 ` Suzuki K Poulose
2026-06-04 15:27 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 14/44] arm64: RMI: Basic infrastructure for creating a realm Steven Price
2026-05-19 6:31 ` Aneesh Kumar K.V
2026-05-28 7:10 ` Marc Zyngier
2026-06-02 14:49 ` Suzuki K Poulose
2026-06-04 15:55 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 15/44] kvm: arm64: Don't expose unsupported capabilities for realm guests Steven Price
2026-05-13 13:17 ` [PATCH v14 16/44] KVM: arm64: Allow passing machine type in KVM creation Steven Price
2026-05-13 13:17 ` [PATCH v14 17/44] arm64: RMI: RTT tear down Steven Price
2026-05-19 6:54 ` Aneesh Kumar K.V
2026-05-26 22:27 ` Wei-Lin Chang
2026-05-26 22:32 ` Wei-Lin Chang
2026-05-13 13:17 ` [PATCH v14 18/44] arm64: RMI: Activate realm on first VCPU run Steven Price
2026-05-13 13:17 ` [PATCH v14 19/44] arm64: RMI: Allocate/free RECs to match vCPUs Steven Price
2026-05-26 22:39 ` Wei-Lin Chang
2026-05-13 13:17 ` [PATCH v14 20/44] arm64: RMI: Support for the VGIC in realms Steven Price
2026-05-28 4:07 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 21/44] KVM: arm64: Support timers in realm RECs Steven Price
2026-05-28 4:11 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 22/44] arm64: RMI: Handle realm enter/exit Steven Price
2026-05-28 4:38 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 23/44] arm64: RMI: Handle RMI_EXIT_RIPAS_CHANGE Steven Price
2026-05-19 9:40 ` Aneesh Kumar K.V
2026-05-27 10:52 ` Wei-Lin Chang
2026-05-13 13:17 ` [PATCH v14 24/44] KVM: arm64: Handle realm MMIO emulation Steven Price
2026-05-28 5:03 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 25/44] KVM: arm64: Expose support for private memory Steven Price
2026-05-13 13:17 ` [PATCH v14 26/44] arm64: RMI: Allow populating initial contents Steven Price
2026-05-28 5:30 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 27/44] arm64: RMI: Set RIPAS of initial memslots Steven Price
2026-05-19 10:02 ` Aneesh Kumar K.V
2026-05-19 10:13 ` Suzuki K Poulose
2026-05-19 12:55 ` Aneesh Kumar K.V
2026-05-19 13:06 ` Suzuki K Poulose
2026-05-13 13:17 ` [PATCH v14 28/44] arm64: RMI: Create the realm descriptor Steven Price
2026-05-26 22:47 ` Wei-Lin Chang
2026-05-28 5:51 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 29/44] arm64: RMI: Runtime faulting of memory Steven Price
2026-05-13 13:17 ` [PATCH v14 30/44] KVM: arm64: Handle realm VCPU load Steven Price
2026-05-13 13:17 ` [PATCH v14 31/44] KVM: arm64: Validate register access for a Realm VM Steven Price
2026-05-13 13:17 ` [PATCH v14 32/44] KVM: arm64: Handle Realm PSCI requests Steven Price
2026-05-28 6:55 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 33/44] KVM: arm64: WARN on injected undef exceptions Steven Price
2026-05-13 13:17 ` [PATCH v14 34/44] arm64: RMI: allow userspace to inject aborts Steven Price
2026-05-13 13:17 ` [PATCH v14 35/44] arm64: RMI: support RSI_HOST_CALL Steven Price
2026-05-13 13:17 ` [PATCH v14 36/44] arm64: RMI: Allow checking SVE on VM instance Steven Price
2026-05-13 13:17 ` [PATCH v14 37/44] arm64: RMI: Prevent Device mappings for Realms Steven Price
2026-05-19 10:25 ` Aneesh Kumar K.V
2026-05-13 13:17 ` [PATCH v14 38/44] arm64: RMI: Propagate number of breakpoints and watchpoints to userspace Steven Price
2026-05-13 13:17 ` [PATCH v14 39/44] arm64: RMI: Set breakpoint parameters through SET_ONE_REG Steven Price
2026-05-13 13:17 ` [PATCH v14 40/44] arm64: RMI: Propagate max SVE vector length from RMM Steven Price
2026-05-13 13:17 ` [PATCH v14 41/44] arm64: RMI: Configure max SVE vector length for a Realm Steven Price
2026-05-13 13:17 ` [PATCH v14 42/44] arm64: RMI: Provide register list for unfinalized RMI RECs Steven Price
2026-05-13 13:17 ` [PATCH v14 43/44] arm64: RMI: Provide accurate register list Steven Price
2026-05-13 13:17 ` [PATCH v14 44/44] arm64: RMI: Enable realms to be created Steven Price
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