linux-kernel - RE: [PATCH hyperv-next v4 14/16] Drivers: hv: Support confidential VMBus channels

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Message-ID:
 <SN6PR02MB415786D31F8D00B0E7815FF0D45CA@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Tue, 22 Jul 2025 17:45:13 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Roman Kisel <romank@...ux.microsoft.com>, "alok.a.tiwari@...cle.com"
	<alok.a.tiwari@...cle.com>, "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de"
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CC: "apais@...rosoft.com" <apais@...rosoft.com>, "benhill@...rosoft.com"
	<benhill@...rosoft.com>, "bperkins@...rosoft.com" <bperkins@...rosoft.com>,
	"sunilmut@...rosoft.com" <sunilmut@...rosoft.com>
Subject: RE: [PATCH hyperv-next v4 14/16] Drivers: hv: Support confidential
 VMBus channels

From: Roman Kisel <romank@...ux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
> 
> To make use of Confidential VMBus channels, initialize the
> co_ring_buffers and co_external_memory fields of the channel
> structure.
> 
> Advertise support upon negotiating the version and compute
> values for those fields and initialize them.
> 
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>

Reviewed-by: Michael Kelley <mhklinux@...look.com>

> ---
>  drivers/hv/channel_mgmt.c | 19 +++++++++++++++++++
>  drivers/hv/connection.c   |  3 +++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index ca2fe10c110a..6ae44eab1626 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -1021,6 +1021,7 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
>  	struct vmbus_channel_offer_channel *offer;
>  	struct vmbus_channel *oldchannel, *newchannel;
>  	size_t offer_sz;
> +	bool co_ring_buffer, co_external_memory;
> 
>  	offer = (struct vmbus_channel_offer_channel *)hdr;
> 
> @@ -1033,6 +1034,22 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
>  		return;
>  	}
> 
> +	co_ring_buffer = is_co_ring_buffer(offer);
> +	co_external_memory = is_co_external_memory(offer);
> +	if (!co_ring_buffer && co_external_memory) {
> +		pr_err("Invalid offer relid=%d: the ring buffer isn't encrypted\n",
> +			offer->child_relid);
> +		return;
> +	}
> +	if (co_ring_buffer || co_external_memory) {
> +		if (vmbus_proto_version < VERSION_WIN10_V6_0 || !vmbus_is_confidential()) {
> +			pr_err("Invalid offer relid=%d: no support for confidential VMBus\n",
> +				offer->child_relid);
> +			atomic_dec(&vmbus_connection.offer_in_progress);
> +			return;
> +		}
> +	}
> +
>  	oldchannel = find_primary_channel_by_offer(offer);
> 
>  	if (oldchannel != NULL) {
> @@ -1111,6 +1128,8 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
>  		pr_err("Unable to allocate channel object\n");
>  		return;
>  	}
> +	newchannel->co_ring_buffer = co_ring_buffer;
> +	newchannel->co_external_memory = co_external_memory;
> 
>  	vmbus_setup_channel_state(newchannel, offer);
> 
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index be490c598785..eeb472019d69 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -105,6 +105,9 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo
> *msginfo, u32 version)
>  		vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
>  	}
> 
> +	if (vmbus_is_confidential() && version >= VERSION_WIN10_V6_0)
> +		msg->feature_flags = VMBUS_FEATURE_FLAG_CONFIDENTIAL_CHANNELS;
> +
>  	/*
>  	 * shared_gpa_boundary is zero in non-SNP VMs, so it's safe to always
>  	 * bitwise OR it
> --
> 2.43.0