Re: [PATCH v6 2/6] arm64: hyperv: Detect Hyper-V via RSI host call in CCA Realms

[Catalin Marinas]

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@xxxxxxxxxxxxxxxxxxx>
> > 
> > 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@xxxxxxx>

-- 
Catalin