linux-kernel - Re: [PATCH v9 16/43] arm64: RME: Handle realm enter/exit

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Message-ID: <d092bb97-d552-49f2-ab93-bb2bd7809c3f@redhat.com>
Date: Wed, 2 Jul 2025 10:41:50 +1000
From: Gavin Shan <gshan@...hat.com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>,
 Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu
 <yuzenghui@...wei.com>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Joey Gouly <joey.gouly@....com>,
 Alexandru Elisei <alexandru.elisei@....com>,
 Christoffer Dall <christoffer.dall@....com>, Fuad Tabba <tabba@...gle.com>,
 linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun
 <alpergun@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
 Emi Kisanuki <fj0570is@...itsu.com>
Subject: Re: [PATCH v9 16/43] arm64: RME: Handle realm enter/exit

On 6/11/25 8:48 PM, Steven Price wrote:
> Entering a realm is done using a SMC call to the RMM. On exit the
> exit-codes need to be handled slightly differently to the normal KVM
> path so define our own functions for realm enter/exit and hook them
> in if the guest is a realm guest.
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> Changes since v8:
>   * Introduce kvm_rec_pre_enter() called before entering an atomic
>     section to handle operations that might require memory allocation
>     (specifically completing a RIPAS change introduced in a later patch).
>   * Updates to align with upstream changes to hpfar_el2 which now (ab)uses
>     HPFAR_EL2_NS as a valid flag.
>   * Fix exit reason when racing with PSCI shutdown to return
>     KVM_EXIT_SHUTDOWN rather than KVM_EXIT_UNKNOWN.
> Changes since v7:
>   * A return of 0 from kvm_handle_sys_reg() doesn't mean the register has
>     been read (although that can never happen in the current code). Tidy
>     up the condition to handle any future refactoring.
> Changes since v6:
>   * Use vcpu_err() rather than pr_err/kvm_err when there is an associated
>     vcpu to the error.
>   * Return -EFAULT for KVM_EXIT_MEMORY_FAULT as per the documentation for
>     this exit type.
>   * Split code handling a RIPAS change triggered by the guest to the
>     following patch.
> Changes since v5:
>   * For a RIPAS_CHANGE request from the guest perform the actual RIPAS
>     change on next entry rather than immediately on the exit. This allows
>     the VMM to 'reject' a RIPAS change by refusing to continue
>     scheduling.
> Changes since v4:
>   * Rename handle_rme_exit() to handle_rec_exit()
>   * Move the loop to copy registers into the REC enter structure from the
>     to rec_exit_handlers callbacks to kvm_rec_enter(). This fixes a bug
>     where the handler exits to user space and user space wants to modify
>     the GPRS.
>   * Some code rearrangement in rec_exit_ripas_change().
> Changes since v2:
>   * realm_set_ipa_state() now provides an output parameter for the
>     top_iap that was changed. Use this to signal the VMM with the correct
>     range that has been transitioned.
>   * Adapt to previous patch changes.
> ---
>   arch/arm64/include/asm/kvm_rme.h |   4 +
>   arch/arm64/kvm/Makefile          |   2 +-
>   arch/arm64/kvm/arm.c             |  22 +++-
>   arch/arm64/kvm/rme-exit.c        | 178 +++++++++++++++++++++++++++++++
>   arch/arm64/kvm/rme.c             |  38 +++++++
>   5 files changed, 239 insertions(+), 5 deletions(-)
>   create mode 100644 arch/arm64/kvm/rme-exit.c
> 

Reviewed-by: Gavin Shan <gshan@...hat.com>