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: Tue, 3 Nov 2026 14:01:38 +0000 [thread overview]
Message-ID: <aunpQixDBFz9VBj8@arm.com> (raw)
In-Reply-To: <c87dc2c3-9211-46d2-9301-46a03d4b0ad7@linux.microsoft.com>
On Mon, Nov 02, 2026 at 11:27:37AM -0800, Kameron Carr wrote:
> On 11/2/2026 4:12 AM, Catalin Marinas wrote:
> > 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.
>
> Thank you for your review and suggestions.
> Your clarification makes sense.
>
> Is this a "Reviewed-by" or an "Acked-by"?
I don't usually ack the hyperv patches as I don't know enough about it
but given that I commented on this particular patch in v5:
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
--
Catalin
next prev parent reply other threads:[~2026-11-03 14:01 UTC|newest]
Thread overview: 12+ 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
2026-11-02 19:27 ` Kameron Carr
2026-11-03 14:01 ` Catalin Marinas [this message]
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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