From: Catalin Marinas <catalin.marinas@arm.com>
To: Kameron Carr <kameroncarr@linux.microsoft.com>
Cc: decui@microsoft.com, haiyangz@microsoft.com,
mhklinux@outlook.com, wei.liu@kernel.org, arnd@arndb.de,
linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
lpieralisi@kernel.org, mark.rutland@arm.com,
sudeep.holla@kernel.org, thuth@redhat.com, will@kernel.org
Subject: Re: [PATCH v6 2/6] arm64: hyperv: Detect Hyper-V via RSI host call in CCA Realms
Date: Mon, 2 Nov 2026 12:12:24 +0000 [thread overview]
Message-ID: <auh-KP-4gFxHtO1z@arm.com> (raw)
In-Reply-To: <20261031001412.4150488-3-kameroncarr@linux.microsoft.com>
On Fri, Oct 30, 2026 at 05:14:08PM -0700, Kameron Carr wrote:
> When booting without ACPI, hyperv_detect_via_smccc() detects Hyper-V by
> querying the SMCCC vendor hypervisor UID. In an Arm CCA Realm the SMCCC
> call is handled by the RMM rather than by the hypervisor, so the
> query never reaches Hyper-V and detection fails.
>
> When running in a Realm, forward ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID
> to the host with RSI_HOST_CALL instead, which is how Hyper-V hypercalls
> are issued from a Realm.
>
> This is done in the Hyper-V code rather than in the generic
> arm_smccc_hypervisor_has_uuid() because the other users expect different
> behavior.
>
> hyperv_init() is an early_initcall and runs before the secondary CPUs
> are brought up, so a single __initdata host call structure is used
> without locking.
>
> ACPI-based detection and non-Realm guests are unaffected.
>
> Signed-off-by: Kameron Carr <kameroncarr@linux.microsoft.com>
This works for me, thanks. I replied to Dexuan clarifying my objection
to v5 do the UUID check generically.
--
Catalin
next prev parent reply other threads:[~2026-11-02 12:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-31 0:14 [PATCH v6 0/6] arm64: hyperv: Add Realm support for Hyper-V Kameron Carr
2026-10-31 0:14 ` [PATCH v6 1/6] arm64: rsi: Add RSI host call structure and helper function Kameron Carr
2026-10-31 4:51 ` Dexuan Cui
2026-11-02 12:10 ` Catalin Marinas
2026-10-31 0:14 ` [PATCH v6 2/6] arm64: hyperv: Detect Hyper-V via RSI host call in CCA Realms Kameron Carr
2026-11-02 12:12 ` Catalin Marinas [this message]
2026-11-02 19:27 ` Kameron Carr
2026-10-31 0:14 ` [PATCH v6 3/6] arm64: hyperv: Add per-CPU RSI host call infrastructure for " Kameron Carr
2026-10-31 0:14 ` [PATCH v6 4/6] Drivers: hv: Mark shared memory as decrypted " Kameron Carr
2026-10-31 0:14 ` [PATCH v6 5/6] arm64: hyperv: Route hypercalls through RSI host call in " Kameron Carr
2026-10-31 0:14 ` [PATCH v6 6/6] arm64: hyperv: Implement hv_is_isolation_supported() for " Kameron Carr
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