From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Steven Price <steven.price@arm.com>,
kvm@vger.kernel.org, kvmarm@lists.linux.dev,
Marc Zyngier <maz@kernel.org>, 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>
Subject: Re: [PATCH v2 09/14] arm64: Enable memory encrypt for Realms
Date: Thu, 16 May 2024 10:06:39 +0100 [thread overview]
Message-ID: <d9d35115-0fb5-4e8e-a99c-ff85ba4a7967@arm.com> (raw)
In-Reply-To: <ZkW6UgrwJT6G9UN-@arm.com>
Hi Catalin
On 16/05/2024 08:48, Catalin Marinas wrote:
> On Wed, May 15, 2024 at 11:47:02AM +0100, Suzuki K Poulose wrote:
>> On 14/05/2024 19:00, Catalin Marinas wrote:
>>> On Fri, Apr 12, 2024 at 09:42:08AM +0100, Steven Price wrote:
>>> Can someone summarise what the point of this protection bit is? The IPA
>>> memory is marked as protected/unprotected already via the RSI call and
>>> presumably the RMM disables/permits sharing with a non-secure hypervisor
>>> accordingly irrespective of which alias the realm guest has the linear
>>> mapping mapped to. What does it do with the top bit of the IPA? Is it
>>> that the RMM will prevent (via Stage 2) access if the IPA does not match
>>> the requested protection? IOW, it unmaps one or the other at Stage 2?
>>
>> The Realm's IPA space is split in half. The lower half is "protected"
>> and all pages backing the "protected" IPA is in the Realm world and
>> thus cannot be shared with the hypervisor. The upper half IPA is
>> "unprotected" (backed by Non-secure PAS pages) and can be accessed
>> by the Host/hyp.
>
> What about emulated device I/O where there's no backing RAM at an IPA.
> Does it need to have the top bit set?
The behaviour depends on the IPA (i.e, protected vs unprotected).
1. Unprotected : All stage2 faults in the Unprotected half are serviced
by the Host, including the areas that may be "Memory" backed. RMM
doesn't provide any guarantees on accesses to the unprotected half.
i.e., host could even inject a Synchronous External abort, if an MMIO
region is not understood by it.
2. Protected : The behaviour depends on the "IPA State" (only applicable
for the protected IPAs). The possible states are RIPAS_RAM, RIPAS_EMPTY
and RIPAS_DESTROYED(not visible for the Realm).
The default IPA state is RIPAS_EMPTY for all IPA and the state is
controlled by Realm with the help of RMM (serviced by Host), except
during the Realm initialisation. i.e., the Host is allowed to "mark"
some IPAs as RIPAS_RAM (for e.g., initial images loaded into the Realm)
during Realm initiliasation (via RMI_RTT_INIT_RIPAS), which gets
measured by the RMM (and affects the Realm Initial Measurement). After
the Realm is activated, the Host can only perform the changes requested
by the Realm (RMM monitors this). Hence, the Realm at boot up, marks all
of its "Described RAM" areas as RIPAS_RAM (via RSI_IPA_STATE_SET), so
that it can go ahead and acccess the RAM as normal.
a) RIPAS_EMPTY: Any access to an IPA in RIPAS_EMPTY generates a
Synchronous External Abort back to the Realm. (In the future, this may
be serviced by another entity in the Realm).
b) RIPAS_RAM: A stage2 fault at a mapped entry triggers a Realm Exit to
the Host (except Instruction Aborts) and the host is allowed to map a
page (that is "scrubbed" by RMM) at stage2 and continue the execution.
[ ---->8 You may skip this ---
c) RIPAS_DESTROYED: An IPA is turned to RIPAS_DESTROYED, if the host
"unmaps" a protected IPA in RIPAS_RAM (via RMI_DATA_DESTROY). This
implies that the Realm contents were destroyed with no way of
restoring back. Any access to such IPA from the Realm also causes
a Realm EXIT, however, the Host is not allowed to map anything back
there and thus the vCPU cannot proceed with the execution.
----<8----
]
>
>> The RSI call (RSI_IPA_STATE_SET) doesn't make an IPA unprotected. It
>> simply "invalidates" a (protected) IPA to "EMPTY" implying the Realm doesn't
>> intend to use the "ipa" as RAM anymore and any access to it from
>> the Realm would trigger an SEA into the Realm. The RSI call triggers an exit
>> to the host with the information and is a hint to the hypervisor to reclaim
>> the page backing the IPA.
>>
>> Now, given we need dynamic "sharing" of pages (instead of a dedicated
>> set of shared pages), "aliasing" of an IPA gives us shared pages.
>> i.e., If OS wants to share a page "x" (protected IPA) with the host,
>> we mark that as EMPTY via RSI call and then access the "x" with top-bit
>> set (aliasing the IPA x). This fault allows the hyp to map the page backing
>> IPA "x" as "unprotected" at ALIAS(x) address.
>
> Does the RMM sanity-checks that the NS hyp mappings are protected or
> unprotected depending on the IPA range?
RMM moderates the mappings in the protected half (as mentioned above).
Any mapping in the unprotected half is not monitored. The host is
allowed unmap, remap with anything in the unprotected half.
>
> I assume that's also the case if the NS hyp is the first one to access a
> page before the realm (e.g. inbound virtio transfer; no page allocated
> yet because of a realm access).
>
Correct. The host need not map anything upfront in the Unprotected half
as it is allowed to map a page "with contents" at any time. A stage2
fault can be serviced by the host to load a page with contents.
Suzuki
next prev parent reply other threads:[~2024-05-16 9:06 UTC|newest]
Thread overview: 134+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 8:40 [v2] Support for Arm CCA VMs on Linux Steven Price
2024-04-11 18:54 ` Itaru Kitayama
2024-04-15 8:14 ` Steven Price
2024-04-12 8:41 ` [PATCH v2 00/14] arm64: Support for running as a guest in Arm CCA Steven Price
2024-04-12 8:42 ` [PATCH v2 01/14] arm64: rsi: Add RSI definitions Steven Price
2024-04-12 8:42 ` [PATCH v2 02/14] arm64: Detect if in a realm and set RIPAS RAM Steven Price
2024-05-10 17:35 ` Catalin Marinas
2024-05-14 10:18 ` Suzuki K Poulose
2024-05-16 14:32 ` Catalin Marinas
2024-05-15 15:03 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 03/14] arm64: realm: Query IPA size from the RMM Steven Price
2024-05-13 14:03 ` Catalin Marinas
2024-05-16 15:13 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 04/14] arm64: Mark all I/O as non-secure shared Steven Price
2024-04-12 8:42 ` [PATCH v2 05/14] fixmap: Allow architecture overriding set_fixmap_io Steven Price
2024-04-12 8:42 ` [PATCH v2 06/14] arm64: Override set_fixmap_io Steven Price
2024-05-13 16:14 ` Catalin Marinas
2024-05-14 10:21 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 07/14] arm64: Make the PHYS_MASK_SHIFT dynamic Steven Price
2024-05-13 16:38 ` Catalin Marinas
2024-05-16 15:34 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 08/14] arm64: Enforce bounce buffers for realm DMA Steven Price
2024-05-13 16:56 ` Catalin Marinas
2024-04-12 8:42 ` [PATCH v2 09/14] arm64: Enable memory encrypt for Realms Steven Price
2024-04-15 3:13 ` kernel test robot
2024-04-25 13:42 ` Suzuki K Poulose
2024-04-25 15:52 ` Steven Price
2024-04-25 16:29 ` Suzuki K Poulose
2024-04-25 18:16 ` Emanuele Rocca
2024-05-14 18:00 ` Catalin Marinas
2024-05-15 10:47 ` Suzuki K Poulose
2024-05-16 7:48 ` Catalin Marinas
2024-05-16 9:06 ` Suzuki K Poulose [this message]
2024-05-20 16:53 ` Catalin Marinas
2024-05-20 20:32 ` Michael Kelley
2024-05-21 10:14 ` Catalin Marinas
2024-05-21 15:58 ` Michael Kelley
2024-04-12 8:42 ` [PATCH v2 10/14] arm64: Force device mappings to be non-secure shared Steven Price
2024-05-15 9:01 ` Catalin Marinas
2024-05-15 11:00 ` Suzuki K Poulose
2024-05-17 9:34 ` Catalin Marinas
2024-04-12 8:42 ` [PATCH v2 11/14] efi: arm64: Map Device with Prot Shared Steven Price
2024-04-12 8:42 ` [PATCH v2 12/14] arm64: realm: Support nonsecure ITS emulation shared Steven Price
2024-05-15 11:01 ` Catalin Marinas
2024-05-22 15:52 ` Steven Price
2024-05-22 17:05 ` Catalin Marinas
2024-05-23 9:57 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 13/14] arm64: rsi: Interfaces to query attestation token Steven Price
2024-05-15 11:10 ` Catalin Marinas
2024-05-22 15:52 ` Steven Price
2024-05-31 16:29 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 14/14] virt: arm-cca-guest: TSM_REPORT support for realms Steven Price
2024-04-24 13:06 ` Thomas Fossati
2024-04-24 13:27 ` Suzuki K Poulose
2024-04-24 13:19 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 00/43] arm64: Support for Arm CCA in KVM Steven Price
2024-04-12 8:42 ` [PATCH v2 01/43] KVM: Prepare for handling only shared mappings in mmu_notifier events Steven Price
2024-04-25 9:48 ` Fuad Tabba
2024-04-25 15:58 ` Steven Price
2024-04-25 22:56 ` Sean Christopherson
2024-04-12 8:42 ` [PATCH v2 02/43] kvm: arm64: pgtable: Track the number of pages in the entry level Steven Price
2024-04-12 8:42 ` [PATCH v2 03/43] kvm: arm64: Include kvm_emulate.h in kvm/arm_psci.h Steven Price
2024-04-12 8:42 ` [PATCH v2 04/43] arm64: RME: Handle Granule Protection Faults (GPFs) Steven Price
2024-04-16 11:17 ` Suzuki K Poulose
2024-04-18 13:17 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 05/43] arm64: RME: Add SMC definitions for calling the RMM Steven Price
2024-04-16 12:38 ` Suzuki K Poulose
2024-04-18 13:17 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 06/43] arm64: RME: Add wrappers for RMI calls Steven Price
2024-04-16 13:14 ` Suzuki K Poulose
2024-04-19 11:18 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 07/43] arm64: RME: Check for RME support at KVM init Steven Price
2024-04-16 13:30 ` Suzuki K Poulose
2024-04-22 15:39 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 08/43] arm64: RME: Define the user ABI Steven Price
2024-04-12 8:42 ` [PATCH v2 09/43] arm64: RME: ioctls to create and configure realms Steven Price
2024-04-17 9:51 ` Suzuki K Poulose
2024-04-22 16:33 ` Steven Price
2024-04-18 16:04 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 10/43] kvm: arm64: Expose debug HW register numbers for Realm Steven Price
2024-04-12 8:42 ` [PATCH v2 11/43] arm64: kvm: Allow passing machine type in KVM creation Steven Price
2024-04-17 10:20 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 12/43] arm64: RME: Keep a spare page delegated to the RMM Steven Price
2024-04-17 10:19 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 13/43] arm64: RME: RTT handling Steven Price
2024-04-17 13:37 ` Suzuki K Poulose
2024-04-24 10:59 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 14/43] arm64: RME: Allocate/free RECs to match vCPUs Steven Price
2024-04-18 9:23 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 15/43] arm64: RME: Support for the VGIC in realms Steven Price
2024-04-12 8:42 ` [PATCH v2 16/43] KVM: arm64: Support timers in realm RECs Steven Price
2024-04-18 9:30 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 17/43] arm64: RME: Allow VMM to set RIPAS Steven Price
2024-04-19 9:34 ` Suzuki K Poulose
2024-04-19 10:20 ` Suzuki K Poulose
2024-05-01 15:47 ` Steven Price
2024-05-02 10:16 ` Suzuki K Poulose
2024-04-25 9:53 ` Fuad Tabba
2024-05-01 14:27 ` Jean-Philippe Brucker
2024-05-01 14:56 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 18/43] arm64: RME: Handle realm enter/exit Steven Price
2024-04-19 13:00 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 19/43] KVM: arm64: Handle realm MMIO emulation Steven Price
2024-04-12 8:42 ` [PATCH v2 20/43] arm64: RME: Allow populating initial contents Steven Price
2024-04-19 13:17 ` Suzuki K Poulose
2024-04-12 8:42 ` [PATCH v2 21/43] arm64: RME: Runtime faulting of memory Steven Price
2024-04-25 10:43 ` Fuad Tabba
2024-05-31 16:03 ` Steven Price
2024-04-12 8:42 ` [PATCH v2 22/43] KVM: arm64: Handle realm VCPU load Steven Price
2024-04-12 8:42 ` [PATCH v2 23/43] KVM: arm64: Validate register access for a Realm VM Steven Price
2024-04-12 8:42 ` [PATCH v2 24/43] KVM: arm64: Handle Realm PSCI requests Steven Price
2024-04-12 8:42 ` [PATCH v2 25/43] KVM: arm64: WARN on injected undef exceptions Steven Price
2024-04-12 8:42 ` [PATCH v2 26/43] arm64: Don't expose stolen time for realm guests Steven Price
2024-04-12 8:42 ` [PATCH v2 27/43] arm64: rme: allow userspace to inject aborts Steven Price
2024-04-12 8:42 ` [PATCH v2 28/43] arm64: rme: support RSI_HOST_CALL Steven Price
2024-04-12 8:42 ` [PATCH v2 29/43] arm64: rme: Allow checking SVE on VM instance Steven Price
2024-04-12 8:42 ` [PATCH v2 30/43] arm64: RME: Always use 4k pages for realms Steven Price
2024-04-12 8:42 ` [PATCH v2 31/43] arm64: rme: Prevent Device mappings for Realms Steven Price
2024-04-12 8:42 ` [PATCH v2 32/43] arm_pmu: Provide a mechanism for disabling the physical IRQ Steven Price
2024-04-12 8:42 ` [PATCH v2 33/43] arm64: rme: Enable PMU support with a realm guest Steven Price
2024-04-13 23:44 ` kernel test robot
2024-04-18 16:06 ` Suzuki K Poulose
2024-04-12 8:43 ` [PATCH v2 34/43] kvm: rme: Hide KVM_CAP_READONLY_MEM for realm guests Steven Price
2024-04-12 8:43 ` [PATCH v2 35/43] arm64: RME: Propagate number of breakpoints and watchpoints to userspace Steven Price
2024-04-12 8:43 ` [PATCH v2 36/43] arm64: RME: Set breakpoint parameters through SET_ONE_REG Steven Price
2024-04-12 8:43 ` [PATCH v2 37/43] arm64: RME: Initialize PMCR.N with number counter supported by RMM Steven Price
2024-04-12 8:43 ` [PATCH v2 38/43] arm64: RME: Propagate max SVE vector length from RMM Steven Price
2024-04-12 8:43 ` [PATCH v2 39/43] arm64: RME: Configure max SVE vector length for a Realm Steven Price
2024-04-12 8:43 ` [PATCH v2 40/43] arm64: RME: Provide register list for unfinalized RME RECs Steven Price
2024-04-12 8:43 ` [PATCH v2 41/43] arm64: RME: Provide accurate register list Steven Price
2024-04-12 8:43 ` [PATCH v2 42/43] arm64: kvm: Expose support for private memory Steven Price
2024-04-25 14:44 ` Fuad Tabba
2024-04-12 8:43 ` [PATCH v2 43/43] KVM: arm64: Allow activating realms Steven Price
2024-04-12 16:52 ` [v2] Support for Arm CCA VMs on Linux Jean-Philippe Brucker
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