[PATCH] firmware: smccc: support both conduits for getting hyp UUID

[PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Anirudh Rayabharam]

From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>

When Linux is running as the root partition under Microsoft Hypervisor
(MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.

Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
of supporting only hvc.

Boot tested on MSHV guest, MSHV root & KVM guest.

Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
---
 drivers/firmware/smccc/smccc.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
index cd65b434dc6e..bdee057db2fd 100644
--- a/drivers/firmware/smccc/smccc.c
+++ b/drivers/firmware/smccc/smccc.c
@@ -72,10 +72,7 @@ bool arm_smccc_hypervisor_has_uuid(const uuid_t *hyp_uuid)
 	struct arm_smccc_res res = {};
 	uuid_t uuid;
 
-	if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_HVC)
-		return false;
-
-	arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
 	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
 		return false;
 
-- 
2.34.1

[PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Roman Kisel]

> From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
>
> When Linux is running as the root partition under Microsoft Hypervisor
> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
>
> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
> of supporting only hvc.
>
> Boot tested on MSHV guest, MSHV root & KVM guest.
>
> Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> ---
>  drivers/firmware/smccc/smccc.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
> index cd65b434dc6e..bdee057db2fd 100644
> --- a/drivers/firmware/smccc/smccc.c
> +++ b/drivers/firmware/smccc/smccc.c
> @@ -72,10 +72,7 @@ bool arm_smccc_hypervisor_has_uuid(const uuid_t *hyp_uuid)
>  	struct arm_smccc_res res = {};
>  	uuid_t uuid;
>
> -	if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_HVC)
> -		return false;
> -
> -	arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
> +	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
>  	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
>  		return false;

The patch is a strict superset of the existing functionality.
Validated on baremetal Linux and KVM, Apple M3 nested virt., various client and
server ARM64 systems running Windows ARM64 with VMs managed by Hyper-V and OpenVMM.

Looks good to me.

Tested-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Sudeep Holla]

(sorry for the delay, found the patch in the spam 🙁)

On Wed, May 21, 2025 at 09:40:48AM +0000, Anirudh Rayabharam wrote:
> From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> 
> When Linux is running as the root partition under Microsoft Hypervisor
> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
> 
> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
> of supporting only hvc.
> 
> Boot tested on MSHV guest, MSHV root & KVM guest.
>

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

Are they any dependent patches or series using this ? Do you plan to
route it via KVM tree if there are any dependency. Or else I can push
it through (arm-)soc tree. Let me know.

-- 
Regards,
Sudeep

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Roman Kisel]

> (sorry for the delay, found the patch in the spam 🙁)

"b4" shows the the mail server used for the patch submission
doesn't pass the DKIM check, so finding the patch in the spam seems
expected :) Thanks for your help!

>
> On Wed, May 21, 2025 at 09:40:48AM +0000, Anirudh Rayabharam wrote:
>> From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
>>
>> When Linux is running as the root partition under Microsoft Hypervisor
>> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
>>
>> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
>> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
>> of supporting only hvc.
>>
>> Boot tested on MSHV guest, MSHV root & KVM guest.
>>
>
> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
>
> Are they any dependent patches or series using this ? Do you plan to
> route it via KVM tree if there are any dependency. Or else I can push
> it through (arm-)soc tree. Let me know.

Anirudh had been OOF for some time and would be for another
week iiuc so I thought I'd reply.

The patch this depends on is 13423063c7cb
("arm64: kvm, smccc: Introduce and use API for getting hypervisor UUID"),
and this patch has already been pulled into the Linus'es tree.

As for routing, (arm-)soc should be good it appears as the change
is contained within the firmware drivers path. Although I'd trust more to your,
Arnd's or Wei's opinion than mine!

>
> --
> Regards,
> Sudeep

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Sudeep Holla]

On Tue, Jun 10, 2025 at 09:06:48AM -0700, Roman Kisel wrote:
> > (sorry for the delay, found the patch in the spam 🙁)
> 
> "b4" shows the the mail server used for the patch submission
> doesn't pass the DKIM check, so finding the patch in the spam seems
> expected :) Thanks for your help!
> 

Thought so looking at the header but I just have very basic knowledge
there, so couldn't comment.

> >
> > On Wed, May 21, 2025 at 09:40:48AM +0000, Anirudh Rayabharam wrote:
> >> From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> >>
> >> When Linux is running as the root partition under Microsoft Hypervisor
> >> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
> >>
> >> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
> >> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
> >> of supporting only hvc.
> >>
> >> Boot tested on MSHV guest, MSHV root & KVM guest.
> >>
> >
> > Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
> >
> > Are they any dependent patches or series using this ? Do you plan to
> > route it via KVM tree if there are any dependency. Or else I can push
> > it through (arm-)soc tree. Let me know.
> 
> Anirudh had been OOF for some time and would be for another
> week iiuc so I thought I'd reply.
> 
> The patch this depends on is 13423063c7cb
> ("arm64: kvm, smccc: Introduce and use API for getting hypervisor UUID"),
> and this patch has already been pulled into the Linus'es tree.
> 

Had a quick look at the commit to refresh my memory and as you mentioned
it is new feature. I was checking to see if this is a fix.

> As for routing, (arm-)soc should be good it appears as the change
> is contained within the firmware drivers path. Although I'd trust more to your,
> Arnd's or Wei's opinion than mine!
> 

I will queue this once I start collecting patches for v6.17 in 1/2 weeks'
time, so expect silence until then 😄.

-- 
Regards,
Sudeep

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Anirudh Rayabharam]

On Tue, Jun 10, 2025 at 09:06:48AM -0700, Roman Kisel wrote:
> > (sorry for the delay, found the patch in the spam 🙁)
> 
> "b4" shows the the mail server used for the patch submission
> doesn't pass the DKIM check, so finding the patch in the spam seems

How do you check this? I mean, what b4 command do you run?

I think it should be fix now. Let's see...

> expected :) Thanks for your help!
> 
> >
> > On Wed, May 21, 2025 at 09:40:48AM +0000, Anirudh Rayabharam wrote:
> >> From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> >>
> >> When Linux is running as the root partition under Microsoft Hypervisor
> >> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
> >>
> >> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
> >> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
> >> of supporting only hvc.
> >>
> >> Boot tested on MSHV guest, MSHV root & KVM guest.
> >>
> >
> > Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
> >
> > Are they any dependent patches or series using this ? Do you plan to
> > route it via KVM tree if there are any dependency. Or else I can push
> > it through (arm-)soc tree. Let me know.
> 
> Anirudh had been OOF for some time and would be for another
> week iiuc so I thought I'd reply.

Thanks Roman!

Regards,
Anirudh

> 
> The patch this depends on is 13423063c7cb
> ("arm64: kvm, smccc: Introduce and use API for getting hypervisor UUID"),
> and this patch has already been pulled into the Linus'es tree.
> 
> As for routing, (arm-)soc should be good it appears as the change
> is contained within the firmware drivers path. Although I'd trust more to your,
> Arnd's or Wei's opinion than mine!
> 
> >
> > --
> > Regards,
> > Sudeep

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Anirudh Rayabharam]

On Wed, Jun 11, 2025 at 01:52:32PM +0100, Sudeep Holla wrote:
> On Tue, Jun 10, 2025 at 09:06:48AM -0700, Roman Kisel wrote:
> > > (sorry for the delay, found the patch in the spam 🙁)
> > 
> > "b4" shows the the mail server used for the patch submission
> > doesn't pass the DKIM check, so finding the patch in the spam seems
> > expected :) Thanks for your help!
> > 
> 
> Thought so looking at the header but I just have very basic knowledge
> there, so couldn't comment.
> 
> > >
> > > On Wed, May 21, 2025 at 09:40:48AM +0000, Anirudh Rayabharam wrote:
> > >> From: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> > >>
> > >> When Linux is running as the root partition under Microsoft Hypervisor
> > >> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
> > >>
> > >> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
> > >> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
> > >> of supporting only hvc.
> > >>
> > >> Boot tested on MSHV guest, MSHV root & KVM guest.
> > >>
> > >
> > > Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
> > >
> > > Are they any dependent patches or series using this ? Do you plan to
> > > route it via KVM tree if there are any dependency. Or else I can push
> > > it through (arm-)soc tree. Let me know.
> > 
> > Anirudh had been OOF for some time and would be for another
> > week iiuc so I thought I'd reply.
> > 
> > The patch this depends on is 13423063c7cb
> > ("arm64: kvm, smccc: Introduce and use API for getting hypervisor UUID"),
> > and this patch has already been pulled into the Linus'es tree.
> > 
> 
> Had a quick look at the commit to refresh my memory and as you mentioned
> it is new feature. I was checking to see if this is a fix.
> 
> > As for routing, (arm-)soc should be good it appears as the change
> > is contained within the firmware drivers path. Although I'd trust more to your,
> > Arnd's or Wei's opinion than mine!
> > 
> 
> I will queue this once I start collecting patches for v6.17 in 1/2 weeks'
> time, so expect silence until then 😄.

Sounds good, thanks!

Regards,
Anirudh.

> 
> -- 
> Regards,
> Sudeep

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Roman Kisel]

On 6/18/2025 5:20 AM, Anirudh Rayabharam wrote:
> On Tue, Jun 10, 2025 at 09:06:48AM -0700, Roman Kisel wrote:
>>> (sorry for the delay, found the patch in the spam 🙁)
>>
>> "b4" shows the the mail server used for the patch submission
>> doesn't pass the DKIM check, so finding the patch in the spam seems
> 
> How do you check this? I mean, what b4 command do you run?
> 
> I think it should be fix now. Let's see...


"b4 am" was showing the failed DKIM check, and all good now!

| $ b4 am 20250521094049.960056-1-anirudh@anirudhrb.com
|
| Grabbing thread from 
lore.kernel.org/all/20250521094049.960056-1-anirudh@anirudhrb.com/t.mbox.gz
| Analyzing 7 messages in the thread
| Looking for additional code-review trailers on lore.kernel.org
| Checking attestation on all messages, may take a moment...
| ---
|   ✓ [PATCH] firmware: smccc: support both conduits for getting hyp UUID
|     + Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
|     + Tested-by: Roman Kisel <romank@linux.microsoft.com> (✓ 
DKIM/linux.microsoft.com)
|     + Reviewed-by: Roman Kisel <romank@linux.microsoft.com> (✓ 
DKIM/linux.microsoft.com)
|   ---
|   ✓ Signed: DKIM/anirudhrb.com
| ---
| Total patches: 1
| ---
|  Link: 
https://lore.kernel.org/r/20250521094049.960056-1-anirudh@anirudhrb.com
|  Base: applies clean to current tree
|        git checkout -b 20250521_anirudh_anirudhrb_com HEAD
|        git am 
./20250521_anirudh_firmware_smccc_support_both_conduits_for_getting_hyp_uuid.mbx
|


[...]
>> Anirudh had been OOF for some time and would be for another
>> week iiuc so I thought I'd reply.
> 
> Thanks Roman!

My pleasure :)

> 
> Regards,
> Anirudh
> 
>>
>> The patch this depends on is 13423063c7cb
>> ("arm64: kvm, smccc: Introduce and use API for getting hypervisor UUID"),
>> and this patch has already been pulled into the Linus'es tree.
>>
>> As for routing, (arm-)soc should be good it appears as the change
>> is contained within the firmware drivers path. Although I'd trust more to your,
>> Arnd's or Wei's opinion than mine!
>>
>>>
>>> --
>>> Regards,
>>> Sudeep

-- 
Thank you,
Roman

Re: [PATCH] firmware: smccc: support both conduits for getting hyp UUID

[Sudeep Holla]

On Wed, 21 May 2025 09:40:48 +0000, Anirudh Rayabharam wrote:
> When Linux is running as the root partition under Microsoft Hypervisor
> (MSHV) a.k.a Hyper-V, smc is used as the conduit for smc calls.
> 
> Extend arm_smccc_hypervisor_has_uuid() to support this usecase. Use
> arm_smccc_1_1_invoke to retrieve and use the appropriate conduit instead
> of supporting only hvc.
> 
> [...]

Applied to sudeep.holla/linux (for-next/smccc/updates), thanks!

[1/1] firmware: smccc: support both conduits for getting hyp UUID
      https://git.kernel.org/sudeep.holla/c/1733432638f3
--
Regards,
Sudeep