* Re: [PATCH v4 1/2] dt-bindings: microsoft: Add vmbus message-connection-id property
From: Hardik Garg @ 2025-07-23 3:08 UTC (permalink / raw)
To: krzk
Cc: apais, conor+dt, decui, devicetree, haiyangz, hargar, hargar,
krzk+dt, kys, linux-hyperv, linux-kernel, robh, ssengar, wei.liu,
cho
In-Reply-To: <095a1455-c6ac-4a7d-a219-ddfd0a93d8d6@kernel.org>
> Host is supposed to have multiple guests, so this feels like you are
> going to prepare for each guest different DTS with different connection
> ID. This feels like poor design. DTS is supposed to be relatively static
> configuration, not runtime choice vmguestid+1.
> The guest cannot access other configuration channels, can it? If it can,
> it would mean it can eavesdrop on other guests? So obviously it cannot.
> Therefore from guest point of view this is completely redundant. Guest
> cannot use any other value, thus guest should not configure it. The
> guest has only one channel and uses only this one which gets to right
> place to the host.
Thank you for your feedback. Let me explain the connection ID in more detail:
1. Message Port Architecture:
- The connection ID specifies which Hyper-V hypervisor message port (mailbox slot) to use for communication between the host and guest
- The hypervisor has multiple message ports, but historically VMBus only used one
- With the introduction of VTL2 (Virtual Trust Level 2), the control plane can now be hosted in VTL2, requiring different message ports for communication
2. Control Plane Communication:
- The VMBus control plane on the host needs to communicate with the VMBus driver in the guest
- When the control plane is hosted in VTL2, it requires a different message port than the standard communication path
- The connection ID tells the guest whether to use the standard or alternate message port for this control plane communication
3. Message Processing:
- Each message is tagged with an ID
- If the guest uses an incorrect ID, the host won't recognize the message and will drop it
- This is not about choosing between multiple available channels - it's about using the correct mailbox slot for communication
4. Security and Isolation:
- Each guest has its private hypervisor mailbox
- Multiple guests using the same connection ID cannot interfere with each other
- The connection ID is more like a "root ID" that helps enumerate devices on the bus, not a channel selector between guests
5. Dynamic Nature:
- The connection ID is specified when the guest starts running
- The host can change it during VM lifecycle events (reset/reboot)
- This is why the VMBus driver needs to know the connection ID every time the kernel starts
- The ID might be different from what it was during the last guest run
Thanks,
Hardik
^ permalink raw reply
* Re: [PATCH net, 0/2] net: Add llist_node init and fix hv_netvsc namespace error
From: Jakub Kicinski @ 2025-07-23 1:44 UTC (permalink / raw)
To: Haiyang Zhang
Cc: linux-hyperv, netdev, haiyangz, kys, wei.liu, decui,
andrew+netdev, sd, viro, chuck.lever, neil, edumazet, pabeni,
horms, davem, kuniyu, linux-kernel
In-Reply-To: <1753228248-20865-1-git-send-email-haiyangz@linux.microsoft.com>
On Tue, 22 Jul 2025 16:50:46 -0700 Haiyang Zhang wrote:
> Add llist_node init to setup_net(), so we can check if the node is on list.
> Then, fix the namespace callback function in hv_netvsc.
Can you not do the moving from a workqueue? Schedule a work, let the
stack finish what it's doing, take rtnl_lock, do you your own moving?
--
pw-bot: cr
^ permalink raw reply
* RE: [EXTERNAL] Re: [PATCH net, 1/2] net: core: Fix missing init of llist_node in setup_net()
From: Haiyang Zhang @ 2025-07-23 0:17 UTC (permalink / raw)
To: Kuniyuki Iwashima, Haiyang Zhang
Cc: linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
KY Srinivasan, wei.liu@kernel.org, Dexuan Cui,
andrew+netdev@lunn.ch, sd@queasysnail.net,
viro@zeniv.linux.org.uk, chuck.lever@oracle.com, neil@brown.name,
edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
horms@kernel.org, davem@davemloft.net,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
In-Reply-To: <CAAVpQUBuyfnv4BBxnOvheEb7JVnokTEiea5Yp4UZdX=5CuWVHg@mail.gmail.com>
> -----Original Message-----
> From: Kuniyuki Iwashima <kuniyu@google.com>
> Sent: Tuesday, July 22, 2025 8:02 PM
> To: Haiyang Zhang <haiyangz@linux.microsoft.com>
> Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; Haiyang Zhang
> <haiyangz@microsoft.com>; KY Srinivasan <kys@microsoft.com>;
> wei.liu@kernel.org; Dexuan Cui <decui@microsoft.com>;
> andrew+netdev@lunn.ch; sd@queasysnail.net; viro@zeniv.linux.org.uk;
> chuck.lever@oracle.com; neil@brown.name; edumazet@google.com;
> kuba@kernel.org; pabeni@redhat.com; horms@kernel.org; davem@davemloft.net;
> linux-kernel@vger.kernel.org; stable@vger.kernel.org
> Subject: [EXTERNAL] Re: [PATCH net, 1/2] net: core: Fix missing init of
> llist_node in setup_net()
>
> [You don't often get email from kuniyu@google.com. Learn why this is
> important at https://aka.ms/LearnAboutSenderIdentification ]
>
> On Tue, Jul 22, 2025 at 4:51 PM Haiyang Zhang
> <haiyangz@linux.microsoft.com> wrote:
> >
> > From: Haiyang Zhang <haiyangz@microsoft.com>
> >
> > Add init_llist_node for lock-less list nodes in struct net in
> > setup_net(), so we can test if a node is on a list or not.
> >
> > Cc: stable@vger.kernel.org
> > Fixes: d6b3358a2813 ("llist: add interface to check if a node is on a
> list.")
>
> No Fixes tag is needed because we didn't have a need to
> test if net is queued for destruction.
I know the original patch wasn't buggy.
This tag is just for the stable backport version hint.
In another thread, Eric Dumazet recommended Fixes tag for patches for "stable":
https://patchwork.kernel.org/project/netdevbpf/patch/1752870014-28909-1-git-send-email-haiyangz@linux.microsoft.com/
Thanks,
- Haiyang
^ permalink raw reply
* Re: [PATCH net, 1/2] net: core: Fix missing init of llist_node in setup_net()
From: Kuniyuki Iwashima @ 2025-07-23 0:01 UTC (permalink / raw)
To: Haiyang Zhang
Cc: linux-hyperv, netdev, haiyangz, kys, wei.liu, decui,
andrew+netdev, sd, viro, chuck.lever, neil, edumazet, kuba,
pabeni, horms, davem, linux-kernel, stable
In-Reply-To: <1753228248-20865-2-git-send-email-haiyangz@linux.microsoft.com>
On Tue, Jul 22, 2025 at 4:51 PM Haiyang Zhang
<haiyangz@linux.microsoft.com> wrote:
>
> From: Haiyang Zhang <haiyangz@microsoft.com>
>
> Add init_llist_node for lock-less list nodes in struct net in
> setup_net(), so we can test if a node is on a list or not.
>
> Cc: stable@vger.kernel.org
> Fixes: d6b3358a2813 ("llist: add interface to check if a node is on a list.")
No Fixes tag is needed because we didn't have a need to
test if net is queued for destruction.
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> ---
> net/core/net_namespace.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index ae54f26709ca..2a821849558f 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -434,6 +434,9 @@ static __net_init int setup_net(struct net *net)
> LIST_HEAD(net_exit_list);
> int error = 0;
>
> + init_llist_node(&net->defer_free_list);
> + init_llist_node(&net->cleanup_list);
> +
> preempt_disable();
> net->net_cookie = gen_cookie_next(&net_cookie);
> preempt_enable();
> --
> 2.34.1
>
^ permalink raw reply
* [PATCH net, 2/2] hv_netvsc: Fix panic during namespace deletion with VF
From: Haiyang Zhang @ 2025-07-22 23:50 UTC (permalink / raw)
To: linux-hyperv, netdev
Cc: haiyangz, kys, wei.liu, decui, andrew+netdev, sd, viro,
chuck.lever, neil, edumazet, kuba, pabeni, horms, davem, kuniyu,
linux-kernel, stable
In-Reply-To: <1753228248-20865-1-git-send-email-haiyangz@linux.microsoft.com>
From: Haiyang Zhang <haiyangz@microsoft.com>
The existing code move the VF NIC to new namespace when NETDEV_REGISTER is
received on netvsc NIC. During deletion of the namespace,
default_device_exit_batch() >> default_device_exit_net() is called. When
netvsc NIC is moved back and registered to the default namespace, it
automatically brings VF NIC back to the default namespace. This will cause
the default_device_exit_net() >> for_each_netdev_safe loop unable to detect
the list end, and hit NULL ptr:
[ 231.449420] mana 7870:00:00.0 enP30832s1: Moved VF to namespace with: eth0
[ 231.449656] BUG: kernel NULL pointer dereference, address: 0000000000000010
[ 231.450246] #PF: supervisor read access in kernel mode
[ 231.450579] #PF: error_code(0x0000) - not-present page
[ 231.450916] PGD 17b8a8067 P4D 0
[ 231.451163] Oops: Oops: 0000 [#1] SMP NOPTI
[ 231.451450] CPU: 82 UID: 0 PID: 1394 Comm: kworker/u768:1 Not tainted 6.16.0-rc4+ #3 VOLUNTARY
[ 231.452042] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 11/21/2024
[ 231.452692] Workqueue: netns cleanup_net
[ 231.452947] RIP: 0010:default_device_exit_batch+0x16c/0x3f0
[ 231.453326] Code: c0 0c f5 b3 e8 d5 db fe ff 48 85 c0 74 15 48 c7 c2 f8 fd ca b2 be 10 00 00 00 48 8d 7d c0 e8 7b 77 25 00 49 8b 86 28 01 00 00 <48> 8b 50 10 4c 8b 2a 4c 8d 62 f0 49 83 ed 10 4c 39 e0 0f 84 d6 00
[ 231.454294] RSP: 0018:ff75fc7c9bf9fd00 EFLAGS: 00010246
[ 231.454610] RAX: 0000000000000000 RBX: 0000000000000002 RCX: 61c8864680b583eb
[ 231.455094] RDX: ff1fa9f71462d800 RSI: ff75fc7c9bf9fd38 RDI: 0000000030766564
[ 231.455686] RBP: ff75fc7c9bf9fd78 R08: 0000000000000000 R09: 0000000000000000
[ 231.456126] R10: 0000000000000001 R11: 0000000000000004 R12: ff1fa9f70088e340
[ 231.456621] R13: ff1fa9f70088e340 R14: ffffffffb3f50c20 R15: ff1fa9f7103e6340
[ 231.457161] FS: 0000000000000000(0000) GS:ff1faa6783a08000(0000) knlGS:0000000000000000
[ 231.457707] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 231.458031] CR2: 0000000000000010 CR3: 0000000179ab2006 CR4: 0000000000b73ef0
[ 231.458434] Call Trace:
[ 231.458600] <TASK>
[ 231.458777] ops_undo_list+0x100/0x220
[ 231.459015] cleanup_net+0x1b8/0x300
[ 231.459285] process_one_work+0x184/0x340
To fix it, skip the VF NIC's namespace change with netvsc when the VF
namespace is being cleaned up, because the default_device_exit_net() will
do it later.
Cc: stable@vger.kernel.org
Fixes: 4c262801ea60 ("hv_netvsc: Fix VF namespace also in synthetic NIC NETDEV_REGISTER event")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
drivers/net/hyperv/netvsc_drv.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 8be9bce66a4e..8fc05a8c0018 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -2788,13 +2788,21 @@ static void netvsc_event_set_vf_ns(struct net_device *ndev)
{
struct net_device_context *ndev_ctx = netdev_priv(ndev);
struct net_device *vf_netdev;
+ struct net *vfnet;
int ret;
vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
if (!vf_netdev)
return;
- if (!net_eq(dev_net(ndev), dev_net(vf_netdev))) {
+ vfnet = dev_net(vf_netdev);
+ /* Do not move it now if its net is being cleaned up,
+ * net_cleanup_work will move it.
+ */
+ if (llist_on_list(&vfnet->cleanup_list))
+ return;
+
+ if (!net_eq(dev_net(ndev), vfnet)) {
ret = dev_change_net_namespace(vf_netdev, dev_net(ndev),
"eth%d");
if (ret)
--
2.34.1
^ permalink raw reply related
* [PATCH net, 1/2] net: core: Fix missing init of llist_node in setup_net()
From: Haiyang Zhang @ 2025-07-22 23:50 UTC (permalink / raw)
To: linux-hyperv, netdev
Cc: haiyangz, kys, wei.liu, decui, andrew+netdev, sd, viro,
chuck.lever, neil, edumazet, kuba, pabeni, horms, davem, kuniyu,
linux-kernel, stable
In-Reply-To: <1753228248-20865-1-git-send-email-haiyangz@linux.microsoft.com>
From: Haiyang Zhang <haiyangz@microsoft.com>
Add init_llist_node for lock-less list nodes in struct net in
setup_net(), so we can test if a node is on a list or not.
Cc: stable@vger.kernel.org
Fixes: d6b3358a2813 ("llist: add interface to check if a node is on a list.")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
net/core/net_namespace.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index ae54f26709ca..2a821849558f 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -434,6 +434,9 @@ static __net_init int setup_net(struct net *net)
LIST_HEAD(net_exit_list);
int error = 0;
+ init_llist_node(&net->defer_free_list);
+ init_llist_node(&net->cleanup_list);
+
preempt_disable();
net->net_cookie = gen_cookie_next(&net_cookie);
preempt_enable();
--
2.34.1
^ permalink raw reply related
* [PATCH net, 0/2] net: Add llist_node init and fix hv_netvsc namespace error
From: Haiyang Zhang @ 2025-07-22 23:50 UTC (permalink / raw)
To: linux-hyperv, netdev
Cc: haiyangz, kys, wei.liu, decui, andrew+netdev, sd, viro,
chuck.lever, neil, edumazet, kuba, pabeni, horms, davem, kuniyu,
linux-kernel
From: Haiyang Zhang <haiyangz@microsoft.com>
Add llist_node init to setup_net(), so we can check if the node is on list.
Then, fix the namespace callback function in hv_netvsc.
Haiyang Zhang (2):
net: core: Fix missing init of llist_node in setup_net()
hv_netvsc: Fix panic during namespace deletion with VF
drivers/net/hyperv/netvsc_drv.c | 10 +++++++++-
net/core/net_namespace.c | 3 +++
2 files changed, 12 insertions(+), 1 deletion(-)
--
2.34.1
^ permalink raw reply
* RE: [PATCH hyperv-next v4 16/16] Drivers: hv: Set the default VMBus version to 6.0
From: Michael Kelley @ 2025-07-22 17:45 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-17-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The confidential VMBus is supported by the protocol version
> 6.0 onwards.
>
> Attempt to establish the VMBus 6.0 connection thus enabling
> the confidential VMBus features when available.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
> drivers/hv/connection.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index eeb472019d69..7cd43463f969 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(vmbus_proto_version);
> * Linux guests and are not listed.
> */
> static __u32 vmbus_versions[] = {
> + VERSION_WIN10_V6_0,
> VERSION_WIN10_V5_3,
> VERSION_WIN10_V5_2,
> VERSION_WIN10_V5_1,
> @@ -65,7 +66,7 @@ static __u32 vmbus_versions[] = {
> * Maximal VMBus protocol version guests can negotiate. Useful to cap the
> * VMBus version for testing and debugging purpose.
> */
> -static uint max_version = VERSION_WIN10_V5_3;
> +static uint max_version = VERSION_WIN10_V6_0;
>
> module_param(max_version, uint, S_IRUGO);
> MODULE_PARM_DESC(max_version,
> --
> 2.43.0
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
^ permalink raw reply
* RE: [PATCH hyperv-next v4 15/16] Drivers: hv: Support establishing the confidential VMBus connection
From: Michael Kelley @ 2025-07-22 17:45 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-16-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> To establish the confidential VMBus connection the CoCo VM guest
> first attempts to connect to the VMBus server run by the paravisor.
> If that fails, the guest falls back to the non-confidential VMBus.
>
> Implement that in the VMBus driver initialization.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
See some spelling/formatting nits below, plus a comment about
your 5 scenarios. Those notwithstanding,
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/vmbus_drv.c | 189 ++++++++++++++++++++++++++++-------------
> 1 file changed, 130 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 13aca5abc7d8..53be3157e22c 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1057,12 +1057,9 @@ static void vmbus_onmessage_work(struct work_struct *work)
> kfree(ctx);
> }
>
> -void vmbus_on_msg_dpc(unsigned long data)
> +static void __vmbus_on_msg_dpc(void *message_page_addr)
> {
> - struct hv_per_cpu_context *hv_cpu = (void *)data;
> - void *page_addr = hv_cpu->hyp_synic_message_page;
> - struct hv_message msg_copy, *msg = (struct hv_message *)page_addr +
> - VMBUS_MESSAGE_SINT;
> + struct hv_message msg_copy, *msg;
> struct vmbus_channel_message_header *hdr;
> enum vmbus_channel_message_type msgtype;
> const struct vmbus_channel_message_table_entry *entry;
> @@ -1070,6 +1067,10 @@ void vmbus_on_msg_dpc(unsigned long data)
> __u8 payload_size;
> u32 message_type;
>
> + if (!message_page_addr)
> + return;
> + msg = (struct hv_message *)message_page_addr + VMBUS_MESSAGE_SINT;
> +
> /*
> * 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
> * it is being used in 'struct vmbus_channel_message_header' definition
> @@ -1195,6 +1196,14 @@ void vmbus_on_msg_dpc(unsigned long data)
> vmbus_signal_eom(msg, message_type);
> }
>
> +void vmbus_on_msg_dpc(unsigned long data)
> +{
> + struct hv_per_cpu_context *hv_cpu = (void *)data;
> +
> + __vmbus_on_msg_dpc(hv_cpu->hyp_synic_message_page);
> + __vmbus_on_msg_dpc(hv_cpu->para_synic_message_page);
> +}
> +
> #ifdef CONFIG_PM_SLEEP
> /*
> * Fake RESCIND_CHANNEL messages to clean up hv_sock channels by force for
> @@ -1233,21 +1242,19 @@ static void vmbus_force_channel_rescinded(struct vmbus_channel *channel)
> #endif /* CONFIG_PM_SLEEP */
>
> /*
> - * Schedule all channels with events pending
> + * Schedule all channels with events pending.
> + * The event page can be directly checked to get the id of
> + * the channel that has the interrupt pending.
> */
> -static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
> +static void vmbus_chan_sched(void *event_page_addr)
> {
> unsigned long *recv_int_page;
> u32 maxbits, relid;
> + union hv_synic_event_flags *event;
>
> - /*
> - * The event page can be directly checked to get the id of
> - * the channel that has the interrupt pending.
> - */
> - void *page_addr = hv_cpu->hyp_synic_event_page;
> - union hv_synic_event_flags *event
> - = (union hv_synic_event_flags *)page_addr +
> - VMBUS_MESSAGE_SINT;
> + if (!event_page_addr)
> + return;
> + event = (union hv_synic_event_flags *)event_page_addr + VMBUS_MESSAGE_SINT;
>
> maxbits = HV_EVENT_FLAGS_COUNT;
> recv_int_page = event->flags;
> @@ -1255,6 +1262,11 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
> if (unlikely(!recv_int_page))
> return;
>
> + /*
> + * Suggested-by: Michael Kelley <mhklinux@outlook.com>
> + * One possible optimization would be to keep track of the largest relID that's in use,
> + * and only scan up to that relID.
> + */
> for_each_set_bit(relid, recv_int_page, maxbits) {
> void (*callback_fn)(void *context);
> struct vmbus_channel *channel;
> @@ -1318,26 +1330,35 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
> }
> }
>
> -static void vmbus_isr(void)
> +static void vmbus_message_sched(struct hv_per_cpu_context *hv_cpu, void
> *message_page_addr)
> {
> - struct hv_per_cpu_context *hv_cpu
> - = this_cpu_ptr(hv_context.cpu_context);
> - void *page_addr;
> struct hv_message *msg;
>
> - vmbus_chan_sched(hv_cpu);
> -
> - page_addr = hv_cpu->hyp_synic_message_page;
> - msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
> + if (!message_page_addr)
> + return;
> + msg = (struct hv_message *)message_page_addr + VMBUS_MESSAGE_SINT;
>
> /* Check if there are actual msgs to be processed */
> if (msg->header.message_type != HVMSG_NONE) {
> if (msg->header.message_type == HVMSG_TIMER_EXPIRED) {
> hv_stimer0_isr();
> vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
> - } else
> + } else {
> tasklet_schedule(&hv_cpu->msg_dpc);
> + }
> }
> +}
> +
> +static void vmbus_isr(void)
> +{
> + struct hv_per_cpu_context *hv_cpu
> + = this_cpu_ptr(hv_context.cpu_context);
> +
> + vmbus_chan_sched(hv_cpu->hyp_synic_event_page);
> + vmbus_chan_sched(hv_cpu->para_synic_event_page);
> +
> + vmbus_message_sched(hv_cpu, hv_cpu->hyp_synic_message_page);
> + vmbus_message_sched(hv_cpu, hv_cpu->para_synic_message_page);
>
> add_interrupt_randomness(vmbus_interrupt);
> }
> @@ -1355,6 +1376,59 @@ static void vmbus_percpu_work(struct work_struct *work)
> hv_synic_init(cpu);
> }
>
> +static int vmbus_alloc_synic_and_connect(void)
> +{
> + int ret, cpu;
> + struct work_struct __percpu *works;
> + int hyperv_cpuhp_online;
> +
> + ret = hv_synic_alloc();
> + if (ret < 0)
> + goto err_alloc;
> +
> + works = alloc_percpu(struct work_struct);
> + if (!works) {
> + ret = -ENOMEM;
> + goto err_alloc;
> + }
> +
> + /*
> + * Initialize the per-cpu interrupt state and stimer state.
> + * Then connect to the host.
> + */
> + cpus_read_lock();
> + for_each_online_cpu(cpu) {
> + struct work_struct *work = per_cpu_ptr(works, cpu);
> +
> + INIT_WORK(work, vmbus_percpu_work);
> + schedule_work_on(cpu, work);
> + }
> +
> + for_each_online_cpu(cpu)
> + flush_work(per_cpu_ptr(works, cpu));
> +
> + /* Register the callbacks for possible CPU online/offline'ing */
> + ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
> + hv_synic_init, hv_synic_cleanup);
> + cpus_read_unlock();
> + free_percpu(works);
> + if (ret < 0)
> + goto err_alloc;
> + hyperv_cpuhp_online = ret;
> +
> + ret = vmbus_connect();
> + if (ret)
> + goto err_connect;
> + return 0;
> +
> +err_connect:
> + cpuhp_remove_state(hyperv_cpuhp_online);
> + return -ENODEV;
> +err_alloc:
> + hv_synic_free();
> + return -ENOMEM;
> +}
> +
> /*
> * vmbus_bus_init -Main vmbus driver initialization routine.
> *
> @@ -1365,8 +1439,7 @@ static void vmbus_percpu_work(struct work_struct *work)
> */
> static int vmbus_bus_init(void)
> {
> - int ret, cpu;
> - struct work_struct __percpu *works;
> + int ret;
>
> ret = hv_init();
> if (ret != 0) {
> @@ -1401,41 +1474,42 @@ static int vmbus_bus_init(void)
> }
> }
>
> - ret = hv_synic_alloc();
> - if (ret)
> - goto err_alloc;
> -
> - works = alloc_percpu(struct work_struct);
> - if (!works) {
> - ret = -ENOMEM;
> - goto err_alloc;
> - }
> -
> /*
> - * Initialize the per-cpu interrupt state and stimer state.
> - * Then connect to the host.
> + * Attempt to establish the confidential VMBus connection first if this VM is
> + * a hardware confidential VM, and the paravisor is present.
> + *
> + * All scenarios here are:
> + * 1. No paravisor,
Inconsistent indentation.
Also, isn't there a "No paravisor, with hardware isolation" scenario? We've
called this "fully enlightened guest" in the past, and code has gone into the
kernel to at least partially support this. The scenario is supported by the
hardware and by Linux guests on other hypervisors. But I'm unsure of the
status on Hyper-V.
> + * 2. Paravisor without VMBus relay, no hardware isolation,
> + * 3. Paravisor without VMBus relay, with hardware isolation,
> + * 4. Paravisor with VMBus relay, no hardware isolation,
> + * 5. Paravisor with VMBus relay, with hardware isolation.
> + *
> + * In the cloud, scenarios 1, 4, 5 are most common, and outside the cloud,
> + * scenario 1 should be the most common at the moment. Detecting of the Confidential
> + * VMBus support below takes that into account running `vmbus_alloc_synic_and_connect()`
> + * only once (barring any faults not related to VMBus) in these cases. That is true
> + * for the scenario 2, too, albeit it might be not as feature-rich as 1, 4, 5.
> + *
> + * However, the code will be doing much more work in scenario 3 where it will have to
> + * first initialize lots of structures for every CPU only to likely tear them down later
> + * and start again, now without attempting to use Confidential VMBus, thus taking a
> + * performance hit. Such systems are rather uncomoon today, don't support more than
s/uncomoon/uncommon/
> + * ~300 CPUs, and are rarely used with many dozens of CPUs. As the time goes on, that
> + * will be even less common. Hence, the preference is to not specialize the code for
> + * that scenario.
> */
> - cpus_read_lock();
> - for_each_online_cpu(cpu) {
> - struct work_struct *work = per_cpu_ptr(works, cpu);
> + ret = -ENODEV;
> + if (ms_hyperv.paravisor_present && (hv_isolation_type_tdx() || hv_isolation_type_snp())) {
> + is_confidential = true;
> + ret = vmbus_alloc_synic_and_connect();
> + is_confidential = !ret;
>
> - INIT_WORK(work, vmbus_percpu_work);
> - schedule_work_on(cpu, work);
> + pr_info("VMBus is confidential: %d\n", is_confidential);
> }
>
> - for_each_online_cpu(cpu)
> - flush_work(per_cpu_ptr(works, cpu));
> -
> - /* Register the callbacks for possible CPU online/offline'ing */
> - ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
> - hv_synic_init, hv_synic_cleanup);
> - cpus_read_unlock();
> - free_percpu(works);
> - if (ret < 0)
> - goto err_alloc;
> - hyperv_cpuhp_online = ret;
> -
> - ret = vmbus_connect();
> + if (!is_confidential)
> + ret = vmbus_alloc_synic_and_connect();
> if (ret)
> goto err_connect;
>
> @@ -1451,9 +1525,6 @@ static int vmbus_bus_init(void)
> return 0;
>
> err_connect:
> - cpuhp_remove_state(hyperv_cpuhp_online);
> -err_alloc:
> - hv_synic_free();
> if (vmbus_irq == -1) {
> hv_remove_vmbus_handler();
> } else {
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 14/16] Drivers: hv: Support confidential VMBus channels
From: Michael Kelley @ 2025-07-22 17:45 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-15-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.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@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.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
^ permalink raw reply
* RE: [PATCH hyperv-next v4 13/16] Drivers: hv: Free msginfo when the buffer fails to decrypt
From: Michael Kelley @ 2025-07-22 17:45 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-14-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The early failure path in __vmbus_establish_gpadl() doesn't deallocate
> msginfo if the buffer fails to decrypt.
>
> Fix the leak by breaking out the cleanup code into a separate function
> and calling it where required.
>
> Fixes: d4dccf353db80 ("Drivers: hv: vmbus: Mark vmbus ring buffer visible to host in Isolation VM")
> Reported-by: Michael Kelly <mkhlinux@outlook.com>
s/Kelly/Kelley/
> Closes: https://lore.kernel.org/linux-hyperv/SN6PR02MB41573796F9787F67E0E97049D472A@SN6PR02MB4157.namprd02.prod.outlook.com/
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
> drivers/hv/channel.c | 32 ++++++++++++++++++++++----------
> 1 file changed, 22 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 051eeba800f2..0eb300b940db 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -409,6 +409,25 @@ static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
> return 0;
> }
>
> +static void vmbus_free_channel_msginfo(struct vmbus_channel_msginfo *msginfo)
> +{
> + unsigned long flags;
> + struct vmbus_channel_msginfo *submsginfo, *tmp;
> +
> + if (!msginfo)
> + return;
> +
> + spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
> + list_del(&msginfo->msglistentry);
> + spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
> + list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
> + msglistentry) {
> + kfree(submsginfo);
> + }
> +
> + kfree(msginfo);
> +}
> +
> /*
> * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
> *
> @@ -428,7 +447,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> struct vmbus_channel_gpadl_header *gpadlmsg;
> struct vmbus_channel_gpadl_body *gpadl_body;
> struct vmbus_channel_msginfo *msginfo = NULL;
> - struct vmbus_channel_msginfo *submsginfo, *tmp;
> + struct vmbus_channel_msginfo *submsginfo;
> struct list_head *curr;
> u32 next_gpadl_handle;
> unsigned long flags;
> @@ -458,6 +477,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> dev_warn(&channel->device_obj->device,
> "Failed to set host visibility for new GPADL %d.\n",
> ret);
> + vmbus_free_channel_msginfo(msginfo);
I don't think this works. At this point, msginfo has not been added to the global
vmbus_connection.chn_msg_list. vmbus_free_channel_msginfo() will try to
remove it from that list using list_del(), and will fault on a NULL pointer.
> return ret;
> }
> }
> @@ -531,15 +551,7 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
>
>
> cleanup:
> - spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
> - list_del(&msginfo->msglistentry);
> - spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
> - list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
> - msglistentry) {
> - kfree(submsginfo);
> - }
> -
> - kfree(msginfo);
> + vmbus_free_channel_msginfo(msginfo);
>
> if (ret) {
> /*
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 12/16] Drivers: hv: Allocate encrypted buffers when requested
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-13-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> Confidential VMBus is built around using buffers not shared with
> the host.
>
> Support allocating encrypted buffers when requested.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/channel.c | 49 +++++++++++++++++++++++----------------
> drivers/hv/hyperv_vmbus.h | 3 ++-
> drivers/hv/ring_buffer.c | 5 ++--
> 3 files changed, 34 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 35f26fa1ffe7..051eeba800f2 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -443,20 +443,23 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> return ret;
> }
>
> - /*
> - * Set the "decrypted" flag to true for the set_memory_decrypted()
> - * success case. In the failure case, the encryption state of the
> - * memory is unknown. Leave "decrypted" as true to ensure the
> - * memory will be leaked instead of going back on the free list.
> - */
> - gpadl->decrypted = true;
> - ret = set_memory_decrypted((unsigned long)kbuffer,
> - PFN_UP(size));
> - if (ret) {
> - dev_warn(&channel->device_obj->device,
> - "Failed to set host visibility for new GPADL %d.\n",
> - ret);
> - return ret;
> + gpadl->decrypted = !((channel->co_external_memory && type == HV_GPADL_BUFFER) ||
> + (channel->co_ring_buffer && type == HV_GPADL_RING));
> + if (gpadl->decrypted) {
> + /*
> + * The "decrypted" flag being true assumes that set_memory_decrypted() succeeds.
> + * But if it fails, the encryption state of the memory is unknown. In that case,
> + * leave "decrypted" as true to ensure the memory is leaked instead of going back
> + * on the free list.
> + */
> + ret = set_memory_decrypted((unsigned long)kbuffer,
> + PFN_UP(size));
> + if (ret) {
> + dev_warn(&channel->device_obj->device,
> + "Failed to set host visibility for new GPADL %d.\n",
> + ret);
> + return ret;
> + }
> }
>
> init_completion(&msginfo->waitevent);
> @@ -544,8 +547,10 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> * left as true so the memory is leaked instead of being
> * put back on the free list.
> */
> - if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
> - gpadl->decrypted = false;
> + if (gpadl->decrypted) {
> + if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
> + gpadl->decrypted = false;
> + }
> }
>
> return ret;
> @@ -676,12 +681,13 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> goto error_clean_ring;
>
> err = hv_ringbuffer_init(&newchannel->outbound,
> - page, send_pages, 0);
> + page, send_pages, 0, newchannel->co_ring_buffer);
> if (err)
> goto error_free_gpadl;
>
> err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
> - recv_pages, newchannel->max_pkt_size);
> + recv_pages, newchannel->max_pkt_size,
> + newchannel->co_ring_buffer);
> if (err)
> goto error_free_gpadl;
>
> @@ -862,8 +868,11 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpad
>
> kfree(info);
>
> - ret = set_memory_encrypted((unsigned long)gpadl->buffer,
> - PFN_UP(gpadl->size));
> + if (gpadl->decrypted)
> + ret = set_memory_encrypted((unsigned long)gpadl->buffer,
> + PFN_UP(gpadl->size));
> + else
> + ret = 0;
> if (ret)
> pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
>
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 2873703d08a9..beae68a70939 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -200,7 +200,8 @@ extern int hv_synic_cleanup(unsigned int cpu);
> void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
>
> int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> - struct page *pages, u32 pagecnt, u32 max_pkt_size);
> + struct page *pages, u32 pagecnt, u32 max_pkt_size,
> + bool confidential);
>
> void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
>
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 3c9b02471760..05c2cd42fc75 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -183,7 +183,8 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
>
> /* Initialize the ring buffer. */
> int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> - struct page *pages, u32 page_cnt, u32 max_pkt_size)
> + struct page *pages, u32 page_cnt, u32 max_pkt_size,
> + bool confidential)
> {
> struct page **pages_wraparound;
> int i;
> @@ -207,7 +208,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
>
> ring_info->ring_buffer = (struct hv_ring_buffer *)
> vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
> - pgprot_decrypted(PAGE_KERNEL));
> + confidential ? PAGE_KERNEL : pgprot_decrypted(PAGE_KERNEL));
>
> kfree(pages_wraparound);
> if (!ring_info->ring_buffer)
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 11/16] Drivers: hv: Functions for setting up and tearing down the paravisor SynIC
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-12-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The confidential VMBus runs with the paravisor SynIC and requires
> configuring it with the paravisor.
>
> Add the functions for configuring the paravisor SynIC. Update
> overall SynIC initialization logic to initialize the SynIC if it
> is present. Finally, break out SynIC interrupt enable/disable
> code into separate functions so that SynIC interrupts can be
> enabled or disabled via the paravisor instead of the hypervisor
> if the paravisor SynIC is present.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
See some comments below about the comments in the code.
Those notwithstanding,
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/hv.c | 197 +++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 185 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 94a81bb3c8c7..9d85d5e62968 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -276,9 +276,8 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
> union hv_synic_simp simp;
> union hv_synic_siefp siefp;
> union hv_synic_sint shared_sint;
> - union hv_synic_scontrol sctrl;
>
> - /* Setup the Synic's message page */
> + /* Setup the Synic's message page with the hypervisor. */
> simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> simp.simp_enabled = 1;
>
> @@ -297,7 +296,7 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
>
> hv_set_msr(HV_MSR_SIMP, simp.as_uint64);
>
> - /* Setup the Synic's event page */
> + /* Setup the Synic's event page with the hypervisor. */
> siefp.as_uint64 = hv_get_msr(HV_MSR_SIEFP);
> siefp.siefp_enabled = 1;
>
> @@ -325,6 +324,11 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
> shared_sint.masked = false;
> shared_sint.auto_eoi = hv_recommend_using_aeoi();
> hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> +}
> +
> +static void hv_hyp_synic_enable_interrupts(void)
> +{
> + union hv_synic_scontrol sctrl;
>
> /* Enable the global synic bit */
> sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
> @@ -333,13 +337,100 @@ void hv_hyp_synic_enable_regs(unsigned int cpu)
> hv_set_msr(HV_MSR_SCONTROL, sctrl.as_uint64);
> }
>
> +/*
> + * The paravisor might not support proxying SynIC, and this
> + * function may fail.
> + */
> +static int hv_para_synic_enable_regs(unsigned int cpu)
> +{
> + int err;
> + union hv_synic_simp simp;
> + union hv_synic_siefp siefp;
> + struct hv_per_cpu_context *hv_cpu
> + = per_cpu_ptr(hv_context.cpu_context, cpu);
> +
> + /* Setup the Synic's message page with the paravisor. */
> + err = hv_para_get_synic_register(HV_MSR_SIMP, &simp.as_uint64);
> + if (err)
> + return err;
> + simp.simp_enabled = 1;
> + simp.base_simp_gpa = virt_to_phys(hv_cpu->para_synic_message_page)
> + >> HV_HYP_PAGE_SHIFT;
> + err = hv_para_set_synic_register(HV_MSR_SIMP, simp.as_uint64);
> + if (err)
> + return err;
> +
> + /* Setup the Synic's event page with the paravisor. */
> + err = hv_para_get_synic_register(HV_MSR_SIEFP, &siefp.as_uint64);
> + if (err)
> + return err;
> + siefp.siefp_enabled = 1;
> + siefp.base_siefp_gpa = virt_to_phys(hv_cpu->para_synic_event_page)
> + >> HV_HYP_PAGE_SHIFT;
> + return hv_para_set_synic_register(HV_MSR_SIEFP, siefp.as_uint64);
> +}
> +
> +static int hv_para_synic_enable_interrupts(void)
> +{
> + union hv_synic_scontrol sctrl;
> + int err;
> +
> + /* Enable the global synic bit */
> + err = hv_para_get_synic_register(HV_MSR_SCONTROL, &sctrl.as_uint64);
> + if (err)
> + return err;
> + sctrl.enable = 1;
> +
> + return hv_para_set_synic_register(HV_MSR_SCONTROL, sctrl.as_uint64);
> +}
> +
> int hv_synic_init(unsigned int cpu)
> {
> + int err;
> +
> + /*
> + * The paravisor may not support the confidential VMBus,
> + * check on that first.
> + */
> + if (vmbus_is_confidential()) {
> + err = hv_para_synic_enable_regs(cpu);
> + if (err)
> + goto fail;
> + }
> +
> + /*
> + * The SINT is set in hv_hyperv_synic_enable_regs() by calling
s/hv_hyperv_synic_enable_regs/hv_hyp_synic_enable_regs/
> + * hv_set_msr(). hv_set_msr() in turn has special case code for the
> + * SINT MSRs that write to the hypervisor version of the MSR *and*
> + * the paravisor version of the MSR (but *without* the proxy bit when
> + * VMBus is confidential). Then the code above enables interrupts
This reference to "the code above" is wrong. It's actually the code below.
Perhaps just do "Then enable interrupts via the paravisor ...." as a new
paragraph in the comment.
> + * via the paravisor if VMBus is confidential, and otherwise via the
> + * hypervisor.
> + */
> +
> hv_hyp_synic_enable_regs(cpu);
> + if (vmbus_is_confidential()) {
> + err = hv_para_synic_enable_interrupts();
> + if (err)
> + goto fail;
> + } else
> + hv_hyp_synic_enable_interrupts();
>
> hv_stimer_legacy_init(cpu, VMBUS_MESSAGE_SINT);
>
> return 0;
> +
> +fail:
> + /*
> + * The failure may only come from enabling the paravisor SynIC.
> + * That in turn means that the confidential VMBus cannot be used
> + * which is not an error: the setup will be re-tried with the
> + * non-confidential VMBus.
> + *
> + * We also don't bother attempting to reset the paravisor registers
> + * as something isn't working there anyway.
> + */
> + return err;
> }
>
> void hv_hyp_synic_disable_regs(unsigned int cpu)
> @@ -349,7 +440,6 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
> union hv_synic_sint shared_sint;
> union hv_synic_simp simp;
> union hv_synic_siefp siefp;
> - union hv_synic_scontrol sctrl;
>
> shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
>
> @@ -361,7 +451,7 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
>
> simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> /*
> - * In Isolation VM, sim and sief pages are allocated by
> + * In Isolation VM, simp and sief pages are allocated by
> * paravisor. These pages also will be used by kdump
> * kernel. So just reset enable bit here and keep page
> * addresses.
> @@ -391,14 +481,64 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
> }
>
> hv_set_msr(HV_MSR_SIEFP, siefp.as_uint64);
> +}
> +
> +static void hv_hyp_synic_disable_interrupts(void)
> +{
> + union hv_synic_scontrol sctrl;
>
> /* Disable the global synic bit */
> sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
> sctrl.enable = 0;
> hv_set_msr(HV_MSR_SCONTROL, sctrl.as_uint64);
> +}
>
> - if (vmbus_irq != -1)
> - disable_percpu_irq(vmbus_irq);
> +static void hv_para_synic_disable_regs(unsigned int cpu)
> +{
> + /*
> + * When a get/set register error is encountered, the function
> + * returns as the paravisor may not support these registers.
> + */
> + int err;
> + union hv_synic_simp simp;
> + union hv_synic_siefp siefp;
> +
> + /*
> + * Don't deallocate memory here as the function is called on
> + * CPU online and offline operations. The guest will find
> + * itself without means of communication when resumed.
> + */
This comment feels unnecessary because deallocating memory in
this function should not be an expectation. Lacking that expectation,
there's no reason to explain why it is not done. Looking at the larger
context, the paired function hv_para_synic_enable_regs() doesn't
allocate memory, and the parallel function hv_hyp_synic_disable_regs()
also doesn't do memory deallocation. FWIW, the first sentence of the
comment is slightly inaccurate because the function is called only
when a CPU goes offline. But I would remove the comment entirely
so as to not imply that it's reasonable to expect the deallocation
should be done here.
CPU offlining is not the justification for why deallocation is not done
here. In my comments on v3 of this patch, my intent was to use CPU
offlining just as an example of why deallocating here would break
things. The deallocation is already properly done in hv_synic_free().
> +
> + /* Disable SynIC's message page in the paravisor. */
> + err = hv_para_get_synic_register(HV_MSR_SIMP, &simp.as_uint64);
> + if (err)
> + return;
> + simp.simp_enabled = 0;
> +
> + err = hv_para_set_synic_register(HV_MSR_SIMP, simp.as_uint64);
> + if (err)
> + return;
> +
> + /* Disable SynIC's event page in the paravisor. */
> + err = hv_para_get_synic_register(HV_MSR_SIEFP, &siefp.as_uint64);
> + if (err)
> + return;
> + siefp.siefp_enabled = 0;
> +
> + hv_para_set_synic_register(HV_MSR_SIEFP, siefp.as_uint64);
> +}
> +
> +static void hv_para_synic_disable_interrupts(void)
> +{
> + union hv_synic_scontrol sctrl;
> + int err;
> +
> + /* Disable the global synic bit */
> + err = hv_para_get_synic_register(HV_MSR_SCONTROL, &sctrl.as_uint64);
> + if (err)
> + return;
> + sctrl.enable = 0;
> + hv_para_set_synic_register(HV_MSR_SCONTROL, sctrl.as_uint64);
> }
>
> #define HV_MAX_TRIES 3
> @@ -411,16 +551,18 @@ void hv_hyp_synic_disable_regs(unsigned int cpu)
> * that the normal interrupt handling mechanism will find and process the channel interrupt
> * "very soon", and in the process clear the bit.
> */
> -static bool hv_synic_event_pending(void)
> +static bool __hv_synic_event_pending(union hv_synic_event_flags *event, int sint)
> {
> - struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
> - union hv_synic_event_flags *event =
> - (union hv_synic_event_flags *)hv_cpu->hyp_synic_event_page + VMBUS_MESSAGE_SINT;
> - unsigned long *recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */
> + unsigned long *recv_int_page;
> bool pending;
> u32 relid;
> int tries = 0;
>
> + if (!event)
> + return false;
> +
> + event += sint;
> + recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */
> retry:
> pending = false;
> for_each_set_bit(relid, recv_int_page, HV_EVENT_FLAGS_COUNT) {
> @@ -437,6 +579,17 @@ static bool hv_synic_event_pending(void)
> return pending;
> }
>
> +static bool hv_synic_event_pending(void)
> +{
> + struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
> + union hv_synic_event_flags *hyp_synic_event_page = hv_cpu->hyp_synic_event_page;
> + union hv_synic_event_flags *para_synic_event_page = hv_cpu->para_synic_event_page;
> +
> + return
> + __hv_synic_event_pending(hyp_synic_event_page, VMBUS_MESSAGE_SINT) ||
> + __hv_synic_event_pending(para_synic_event_page, VMBUS_MESSAGE_SINT);
> +}
> +
> static int hv_pick_new_cpu(struct vmbus_channel *channel)
> {
> int ret = -EBUSY;
> @@ -529,7 +682,27 @@ int hv_synic_cleanup(unsigned int cpu)
> always_cleanup:
> hv_stimer_legacy_cleanup(cpu);
>
> + /*
> + * First, disable the event and message pages
> + * used for communicating with the host, and then
> + * disable the host interrupts if VMBus is not
> + * confidential.
> + */
> hv_hyp_synic_disable_regs(cpu);
> + if (!vmbus_is_confidential())
> + hv_hyp_synic_disable_interrupts();
> +
> + /*
> + * Perform the same steps for the Confidential VMBus.
> + * The sequencing provides the gurantee that no data
s/gurantee/guarantee/
> + * may be posted for processing before disabling interrupts.
> + */
> + if (vmbus_is_confidential()) {
> + hv_para_synic_disable_regs(cpu);
> + hv_para_synic_disable_interrupts();
> + }
> + if (vmbus_irq != -1)
> + disable_percpu_irq(vmbus_irq);
>
> return ret;
> }
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 10/16] Drivers: hv: Rename the SynIC enable and disable routines
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-11-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The confidential VMBus requires support for the both hypervisor
> facing SynIC and the paravisor one.
>
> Rename the functions that enable and disable SynIC with the
> hypervisor. No functional changes.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/channel_mgmt.c | 2 +-
> drivers/hv/hv.c | 11 ++++++-----
> drivers/hv/hyperv_vmbus.h | 4 ++--
> drivers/hv/vmbus_drv.c | 6 +++---
> 4 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 6f87220e2ca3..ca2fe10c110a 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -845,7 +845,7 @@ static void vmbus_wait_for_unload(void)
> /*
> * In a CoCo VM the hyp_synic_message_page is not allocated
> * in hv_synic_alloc(). Instead it is set/cleared in
> - * hv_synic_enable_regs() and hv_synic_disable_regs()
> + * hv_hyp_synic_enable_regs() and
> hv_hyp_synic_disable_regs()
> * such that it is set only when the CPU is online. If
> * not all present CPUs are online, the message page
> * might be NULL, so skip such CPUs.
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index a8669843c56e..94a81bb3c8c7 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -266,9 +266,10 @@ void hv_synic_free(void)
> }
>
> /*
> - * hv_synic_enable_regs - Initialize the Synthetic Interrupt Controller.
> + * hv_hyp_synic_enable_regs - Initialize the Synthetic Interrupt Controller
> + * with the hypervisor.
> */
> -void hv_synic_enable_regs(unsigned int cpu)
> +void hv_hyp_synic_enable_regs(unsigned int cpu)
> {
> struct hv_per_cpu_context *hv_cpu =
> per_cpu_ptr(hv_context.cpu_context, cpu);
> @@ -334,14 +335,14 @@ void hv_synic_enable_regs(unsigned int cpu)
>
> int hv_synic_init(unsigned int cpu)
> {
> - hv_synic_enable_regs(cpu);
> + hv_hyp_synic_enable_regs(cpu);
>
> hv_stimer_legacy_init(cpu, VMBUS_MESSAGE_SINT);
>
> return 0;
> }
>
> -void hv_synic_disable_regs(unsigned int cpu)
> +void hv_hyp_synic_disable_regs(unsigned int cpu)
> {
> struct hv_per_cpu_context *hv_cpu =
> per_cpu_ptr(hv_context.cpu_context, cpu);
> @@ -528,7 +529,7 @@ int hv_synic_cleanup(unsigned int cpu)
> always_cleanup:
> hv_stimer_legacy_cleanup(cpu);
>
> - hv_synic_disable_regs(cpu);
> + hv_hyp_synic_disable_regs(cpu);
>
> return ret;
> }
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 16b5cf1bca19..2873703d08a9 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -189,10 +189,10 @@ extern int hv_synic_alloc(void);
>
> extern void hv_synic_free(void);
>
> -extern void hv_synic_enable_regs(unsigned int cpu);
> +extern void hv_hyp_synic_enable_regs(unsigned int cpu);
> extern int hv_synic_init(unsigned int cpu);
>
> -extern void hv_synic_disable_regs(unsigned int cpu);
> +extern void hv_hyp_synic_disable_regs(unsigned int cpu);
> extern int hv_synic_cleanup(unsigned int cpu);
>
> /* Interface */
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 72940a64b0b6..13aca5abc7d8 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2809,7 +2809,7 @@ static void hv_crash_handler(struct pt_regs *regs)
> */
> cpu = smp_processor_id();
> hv_stimer_cleanup(cpu);
> - hv_synic_disable_regs(cpu);
> + hv_hyp_synic_disable_regs(cpu);
> };
>
> static int hv_synic_suspend(void)
> @@ -2834,14 +2834,14 @@ static int hv_synic_suspend(void)
> * interrupts-disabled context.
> */
>
> - hv_synic_disable_regs(0);
> + hv_hyp_synic_disable_regs(0);
>
> return 0;
> }
>
> static void hv_synic_resume(void)
> {
> - hv_synic_enable_regs(0);
> + hv_hyp_synic_enable_regs(0);
>
> /*
> * Note: we don't need to call hv_stimer_init(0), because the timer
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 09/16] Drivers: hv: Check message and event pages for non-NULL before iounmap()
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-10-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> It might happen that some hyp SynIC pages aren't allocated.
>
> Check for that and only then call iounmap().
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
> drivers/hv/hv.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 820711e954d1..a8669843c56e 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -367,8 +367,10 @@ void hv_synic_disable_regs(unsigned int cpu)
> */
> simp.simp_enabled = 0;
> if (ms_hyperv.paravisor_present || hv_root_partition()) {
> - iounmap(hv_cpu->hyp_synic_message_page);
> - hv_cpu->hyp_synic_message_page = NULL;
> + if (hv_cpu->hyp_synic_message_page) {
> + iounmap(hv_cpu->hyp_synic_message_page);
> + hv_cpu->hyp_synic_message_page = NULL;
> + }
> } else {
> simp.base_simp_gpa = 0;
> }
> @@ -379,8 +381,10 @@ void hv_synic_disable_regs(unsigned int cpu)
> siefp.siefp_enabled = 0;
>
> if (ms_hyperv.paravisor_present || hv_root_partition()) {
> - iounmap(hv_cpu->hyp_synic_event_page);
> - hv_cpu->hyp_synic_event_page = NULL;
> + if (hv_cpu->hyp_synic_event_page) {
> + iounmap(hv_cpu->hyp_synic_event_page);
> + hv_cpu->hyp_synic_event_page = NULL;
> + }
> } else {
> siefp.base_siefp_gpa = 0;
> }
> --
> 2.43.0
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
^ permalink raw reply
* RE: [PATCH hyperv-next v4 08/16] Drivers: hv: remove stale comment
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-9-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The comment about the x2v shim is ancient and long since incorrect.
>
> Remove the incorrect comment.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
> drivers/hv/hv.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 816f8a14ff63..820711e954d1 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -266,11 +266,7 @@ void hv_synic_free(void)
> }
>
> /*
> - * hv_synic_init - Initialize the Synthetic Interrupt Controller.
> - *
> - * If it is already initialized by another entity (ie x2v shim), we need to
> - * retrieve the initialized message and event pages. Otherwise, we create and
> - * initialize the message and event pages.
> + * hv_synic_enable_regs - Initialize the Synthetic Interrupt Controller.
> */
> void hv_synic_enable_regs(unsigned int cpu)
> {
> --
> 2.43.0
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
^ permalink raw reply
* RE: [PATCH hyperv-next v4 07/16] Drivers: hv: Post messages through the confidential VMBus if available
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-8-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> When the confidential VMBus is available, the guest should post
> messages to the paravisor.
>
> Update hv_post_message() to post messages to the paravisor rather than
> through GHCB or TD calls.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/hv.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index e9ee0177d765..816f8a14ff63 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -74,7 +74,11 @@ int hv_post_message(union hv_connection_id connection_id,
> aligned_msg->payload_size = payload_size;
> memcpy((void *)aligned_msg->payload, payload, payload_size);
>
> - if (ms_hyperv.paravisor_present) {
> + if (ms_hyperv.paravisor_present && !vmbus_is_confidential()) {
> + /*
> + * If the VMBus isn't confidential, use the CoCo-specific
> + * mechanism to communicate with the hypervisor.
> + */
> if (hv_isolation_type_tdx())
> status = hv_tdx_hypercall(HVCALL_POST_MESSAGE,
> virt_to_phys(aligned_msg), 0);
> @@ -85,6 +89,11 @@ int hv_post_message(union hv_connection_id connection_id,
> else
> status = HV_STATUS_INVALID_PARAMETER;
> } else {
> + /*
> + * If there is no paravisor, this will go to the hypervisor.
> + * In the Confidential VMBus case, there is the paravisor
> + * to which this will trap.
> + */
> status = hv_do_hypercall(HVCALL_POST_MESSAGE,
> aligned_msg, NULL);
> }
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 06/16] Drivers: hv: Allocate the paravisor SynIC pages when required
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-7-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> Confidential VMBus requires interacting with two SynICs -- one
> provided by the host hypervisor, and one provided by the paravisor.
> Each SynIC requires its own message and event pages.
>
> Refactor and extend the existing code to add allocating and freeing
> the message and event pages for the paravisor SynIC when it is
> present.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Modulo a nit called out below,
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/hv.c | 184 +++++++++++++++++++-------------------
> drivers/hv/hyperv_vmbus.h | 18 ++++
> 2 files changed, 112 insertions(+), 90 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 964b9102477d..e9ee0177d765 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -94,10 +94,70 @@ int hv_post_message(union hv_connection_id connection_id,
> return hv_result(status);
> }
>
> +static int hv_alloc_page(void **page, bool decrypt, const char *note)
> +{
> + int ret = 0;
> +
> + /*
> + * After the page changes its encryption status, its contents might
> + * appear scrambled on some hardware. Thus `get_zeroed_page` would
> + * zero the page out in vain, so do that explicitly exactly once.
> + *
> + * By default, the page is allocated encrypted in a CoCo VM.
> + */
> + *page = (void *)__get_free_page(GFP_KERNEL);
> + if (!*page)
> + return -ENOMEM;
> +
> + if (decrypt)
> + ret = set_memory_decrypted((unsigned long)*page, 1);
> + if (ret)
> + goto failed;
> +
> + memset(*page, 0, PAGE_SIZE);
> + return 0;
> +
> +failed:
> + /*
> + * Report the failure but don't put the page back on the free list as
> + * its encryption status is unknown.
> + */
> + pr_err("allocation failed for %s page, error %d, decrypted %d\n",
> + note, ret, decrypt);
> + *page = NULL;
> + return ret;
> +}
> +
> +static int hv_free_page(void **page, bool encrypt, const char *note)
> +{
> + int ret = 0;
> +
> + if (!*page)
> + return 0;
> +
> + if (encrypt)
> + ret = set_memory_encrypted((unsigned long)*page, 1);
> +
> + /*
> + * In the case of the failure, the page is leaked. Something is wrong,
> + * prefer to lose the page with the unknown encryption status and stay afloat.
> + */
> + if (ret) {
> + pr_err("deallocation failed for %s page, error %d, encrypt %d\n",
> + note, ret, encrypt);
> + } else
Nit: The braces here are unnecessary.
> + free_page((unsigned long)*page);
> +
> + *page = NULL;
> +
> + return ret;
> +}
> +
> int hv_synic_alloc(void)
> {
> int cpu, ret = -ENOMEM;
> struct hv_per_cpu_context *hv_cpu;
> + const bool decrypt = !vmbus_is_confidential();
>
> /*
> * First, zero all per-cpu memory areas so hv_synic_free() can
> @@ -123,73 +183,37 @@ int hv_synic_alloc(void)
> vmbus_on_msg_dpc, (unsigned long)hv_cpu);
>
> if (ms_hyperv.paravisor_present && hv_isolation_type_tdx()) {
> - hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
> - if (!hv_cpu->post_msg_page) {
> - pr_err("Unable to allocate post msg page\n");
> + ret = hv_alloc_page(&hv_cpu->post_msg_page,
> + decrypt, "post msg");
> + if (ret)
> goto err;
> - }
> -
> - ret = set_memory_decrypted((unsigned long)hv_cpu->post_msg_page, 1);
> - if (ret) {
> - pr_err("Failed to decrypt post msg page: %d\n", ret);
> - /* Just leak the page, as it's unsafe to free the page. */
> - hv_cpu->post_msg_page = NULL;
> - goto err;
> - }
> -
> - memset(hv_cpu->post_msg_page, 0, PAGE_SIZE);
> }
>
> /*
> - * Synic message and event pages are allocated by paravisor.
> - * Skip these pages allocation here.
> + * If these SynIC pages are not allocated, SIEF and SIM pages
> + * are configured using what the root partition or the paravisor
> + * provides upon reading the SIEFP and SIMP registers.
> */
> if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
> - hv_cpu->hyp_synic_message_page =
> - (void *)get_zeroed_page(GFP_ATOMIC);
> - if (!hv_cpu->hyp_synic_message_page) {
> - pr_err("Unable to allocate SYNIC message page\n");
> + ret = hv_alloc_page(&hv_cpu->hyp_synic_message_page,
> + decrypt, "hypervisor SynIC msg");
> + if (ret)
> goto err;
> - }
> -
> - hv_cpu->hyp_synic_event_page =
> - (void *)get_zeroed_page(GFP_ATOMIC);
> - if (!hv_cpu->hyp_synic_event_page) {
> - pr_err("Unable to allocate SYNIC event page\n");
> -
> - free_page((unsigned long)hv_cpu->hyp_synic_message_page);
> - hv_cpu->hyp_synic_message_page = NULL;
> + ret = hv_alloc_page(&hv_cpu->hyp_synic_event_page,
> + decrypt, "hypervisor SynIC event");
> + if (ret)
> goto err;
> - }
> }
>
> - if (!ms_hyperv.paravisor_present &&
> - (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
> - ret = set_memory_decrypted((unsigned long)
> - hv_cpu->hyp_synic_message_page, 1);
> - if (ret) {
> - pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
> - hv_cpu->hyp_synic_message_page = NULL;
> -
> - /*
> - * Free the event page here so that hv_synic_free()
> - * won't later try to re-encrypt it.
> - */
> - free_page((unsigned long)hv_cpu->hyp_synic_event_page);
> - hv_cpu->hyp_synic_event_page = NULL;
> + if (vmbus_is_confidential()) {
> + ret = hv_alloc_page(&hv_cpu->para_synic_message_page,
> + false, "paravisor SynIC msg");
> + if (ret)
> goto err;
> - }
> -
> - ret = set_memory_decrypted((unsigned long)
> - hv_cpu->hyp_synic_event_page, 1);
> - if (ret) {
> - pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
> - hv_cpu->hyp_synic_event_page = NULL;
> + ret = hv_alloc_page(&hv_cpu->para_synic_event_page,
> + false, "paravisor SynIC event");
> + if (ret)
> goto err;
> - }
> -
> - memset(hv_cpu->hyp_synic_message_page, 0, PAGE_SIZE);
> - memset(hv_cpu->hyp_synic_event_page, 0, PAGE_SIZE);
> }
> }
>
> @@ -205,48 +229,28 @@ int hv_synic_alloc(void)
>
> void hv_synic_free(void)
> {
> - int cpu, ret;
> + int cpu;
> + const bool encrypt = !vmbus_is_confidential();
>
> for_each_present_cpu(cpu) {
> struct hv_per_cpu_context *hv_cpu =
> per_cpu_ptr(hv_context.cpu_context, cpu);
>
> - /* It's better to leak the page if the encryption fails. */
> - if (ms_hyperv.paravisor_present && hv_isolation_type_tdx()) {
> - if (hv_cpu->post_msg_page) {
> - ret = set_memory_encrypted((unsigned long)
> - hv_cpu->post_msg_page, 1);
> - if (ret) {
> - pr_err("Failed to encrypt post msg page: %d\n", ret);
> - hv_cpu->post_msg_page = NULL;
> - }
> - }
> + if (ms_hyperv.paravisor_present && hv_isolation_type_tdx())
> + hv_free_page(&hv_cpu->post_msg_page,
> + encrypt, "post msg");
> + if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
> + hv_free_page(&hv_cpu->hyp_synic_event_page,
> + encrypt, "hypervisor SynIC event");
> + hv_free_page(&hv_cpu->hyp_synic_message_page,
> + encrypt, "hypervisor SynIC msg");
> }
> -
> - if (!ms_hyperv.paravisor_present &&
> - (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
> - if (hv_cpu->hyp_synic_message_page) {
> - ret = set_memory_encrypted((unsigned long)
> - hv_cpu->hyp_synic_message_page, 1);
> - if (ret) {
> - pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
> - hv_cpu->hyp_synic_message_page = NULL;
> - }
> - }
> -
> - if (hv_cpu->hyp_synic_event_page) {
> - ret = set_memory_encrypted((unsigned long)
> - hv_cpu->hyp_synic_event_page, 1);
> - if (ret) {
> - pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
> - hv_cpu->hyp_synic_event_page = NULL;
> - }
> - }
> + if (vmbus_is_confidential()) {
> + hv_free_page(&hv_cpu->para_synic_event_page,
> + false, "paravisor SynIC event");
> + hv_free_page(&hv_cpu->para_synic_message_page,
> + false, "paravisor SynIC msg");
> }
> -
> - free_page((unsigned long)hv_cpu->post_msg_page);
> - free_page((unsigned long)hv_cpu->hyp_synic_event_page);
> - free_page((unsigned long)hv_cpu->hyp_synic_message_page);
> }
>
> kfree(hv_context.hv_numa_map);
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index fc3cdb26ff1a..16b5cf1bca19 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -120,8 +120,26 @@ enum {
> * Per cpu state for channel handling
> */
> struct hv_per_cpu_context {
> + /*
> + * SynIC pages for communicating with the host.
> + *
> + * These pages are accessible to the host partition and the hypervisor.
> + * They may be used for exchanging data with the host partition and the
> + * hypervisor even when they aren't trusted yet the guest partition
> + * must be prepared to handle the malicious behavior.
> + */
> void *hyp_synic_message_page;
> void *hyp_synic_event_page;
> + /*
> + * SynIC pages for communicating with the paravisor.
> + *
> + * These pages may be accessed from within the guest partition only in
> + * CoCo VMs. Neither the host partition nor the hypervisor can access
> + * these pages in that case; they are used for exchanging data with the
> + * paravisor.
> + */
> + void *para_synic_message_page;
> + void *para_synic_event_page;
>
> /*
> * The page is only used in hv_post_message() for a TDX VM (with the
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 05/16] Drivers: hv: Rename fields for SynIC message and event pages
From: Michael Kelley @ 2025-07-22 17:44 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-6-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> Confidential VMBus requires interacting with two SynICs -- one
> provided by the host hypervisor, and one provided by the paravisor.
> Each SynIC requires its own message and event pages.
>
> Rename the existing host-accessible SynIC message and event pages
> with the "hyp_" prefix to clearly distinguish them from the paravisor
> ones. The field name is also changed in mshv_root.* for consistency.
>
> No functional changes.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/channel_mgmt.c | 6 ++--
> drivers/hv/hv.c | 66 +++++++++++++++++++--------------------
> drivers/hv/hyperv_vmbus.h | 4 +--
> drivers/hv/mshv_root.h | 2 +-
> drivers/hv/mshv_synic.c | 6 ++--
> drivers/hv/vmbus_drv.c | 6 ++--
> 6 files changed, 45 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 6e084c207414..6f87220e2ca3 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -843,14 +843,14 @@ static void vmbus_wait_for_unload(void)
> = per_cpu_ptr(hv_context.cpu_context, cpu);
>
> /*
> - * In a CoCo VM the synic_message_page is not allocated
> + * In a CoCo VM the hyp_synic_message_page is not allocated
> * in hv_synic_alloc(). Instead it is set/cleared in
> * hv_synic_enable_regs() and hv_synic_disable_regs()
> * such that it is set only when the CPU is online. If
> * not all present CPUs are online, the message page
> * might be NULL, so skip such CPUs.
> */
> - page_addr = hv_cpu->synic_message_page;
> + page_addr = hv_cpu->hyp_synic_message_page;
> if (!page_addr)
> continue;
>
> @@ -891,7 +891,7 @@ static void vmbus_wait_for_unload(void)
> struct hv_per_cpu_context *hv_cpu
> = per_cpu_ptr(hv_context.cpu_context, cpu);
>
> - page_addr = hv_cpu->synic_message_page;
> + page_addr = hv_cpu->hyp_synic_message_page;
> if (!page_addr)
> continue;
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 308c8f279df8..964b9102477d 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -145,20 +145,20 @@ int hv_synic_alloc(void)
> * Skip these pages allocation here.
> */
> if (!ms_hyperv.paravisor_present && !hv_root_partition()) {
> - hv_cpu->synic_message_page =
> + hv_cpu->hyp_synic_message_page =
> (void *)get_zeroed_page(GFP_ATOMIC);
> - if (!hv_cpu->synic_message_page) {
> + if (!hv_cpu->hyp_synic_message_page) {
> pr_err("Unable to allocate SYNIC message page\n");
> goto err;
> }
>
> - hv_cpu->synic_event_page =
> + hv_cpu->hyp_synic_event_page =
> (void *)get_zeroed_page(GFP_ATOMIC);
> - if (!hv_cpu->synic_event_page) {
> + if (!hv_cpu->hyp_synic_event_page) {
> pr_err("Unable to allocate SYNIC event page\n");
>
> - free_page((unsigned long)hv_cpu-
> >synic_message_page);
> - hv_cpu->synic_message_page = NULL;
> + free_page((unsigned long)hv_cpu-
> >hyp_synic_message_page);
> + hv_cpu->hyp_synic_message_page = NULL;
> goto err;
> }
> }
> @@ -166,30 +166,30 @@ int hv_synic_alloc(void)
> if (!ms_hyperv.paravisor_present &&
> (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
> ret = set_memory_decrypted((unsigned long)
> - hv_cpu->synic_message_page, 1);
> + hv_cpu->hyp_synic_message_page, 1);
> if (ret) {
> pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
> - hv_cpu->synic_message_page = NULL;
> + hv_cpu->hyp_synic_message_page = NULL;
>
> /*
> * Free the event page here so that hv_synic_free()
> * won't later try to re-encrypt it.
> */
> - free_page((unsigned long)hv_cpu->synic_event_page);
> - hv_cpu->synic_event_page = NULL;
> + free_page((unsigned long)hv_cpu-
> >hyp_synic_event_page);
> + hv_cpu->hyp_synic_event_page = NULL;
> goto err;
> }
>
> ret = set_memory_decrypted((unsigned long)
> - hv_cpu->synic_event_page, 1);
> + hv_cpu->hyp_synic_event_page, 1);
> if (ret) {
> pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
> - hv_cpu->synic_event_page = NULL;
> + hv_cpu->hyp_synic_event_page = NULL;
> goto err;
> }
>
> - memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
> - memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
> + memset(hv_cpu->hyp_synic_message_page, 0, PAGE_SIZE);
> + memset(hv_cpu->hyp_synic_event_page, 0, PAGE_SIZE);
> }
> }
>
> @@ -225,28 +225,28 @@ void hv_synic_free(void)
>
> if (!ms_hyperv.paravisor_present &&
> (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
> - if (hv_cpu->synic_message_page) {
> + if (hv_cpu->hyp_synic_message_page) {
> ret = set_memory_encrypted((unsigned long)
> - hv_cpu->synic_message_page, 1);
> + hv_cpu->hyp_synic_message_page, 1);
> if (ret) {
> pr_err("Failed to encrypt SYNIC msg page:
> %d\n", ret);
> - hv_cpu->synic_message_page = NULL;
> + hv_cpu->hyp_synic_message_page = NULL;
> }
> }
>
> - if (hv_cpu->synic_event_page) {
> + if (hv_cpu->hyp_synic_event_page) {
> ret = set_memory_encrypted((unsigned long)
> - hv_cpu->synic_event_page, 1);
> + hv_cpu->hyp_synic_event_page, 1);
> if (ret) {
> pr_err("Failed to encrypt SYNIC event page:
> %d\n", ret);
> - hv_cpu->synic_event_page = NULL;
> + hv_cpu->hyp_synic_event_page = NULL;
> }
> }
> }
>
> free_page((unsigned long)hv_cpu->post_msg_page);
> - free_page((unsigned long)hv_cpu->synic_event_page);
> - free_page((unsigned long)hv_cpu->synic_message_page);
> + free_page((unsigned long)hv_cpu->hyp_synic_event_page);
> + free_page((unsigned long)hv_cpu->hyp_synic_message_page);
> }
>
> kfree(hv_context.hv_numa_map);
> @@ -276,12 +276,12 @@ void hv_synic_enable_regs(unsigned int cpu)
> /* Mask out vTOM bit. ioremap_cache() maps decrypted */
> u64 base = (simp.base_simp_gpa << HV_HYP_PAGE_SHIFT) &
> ~ms_hyperv.shared_gpa_boundary;
> - hv_cpu->synic_message_page =
> + hv_cpu->hyp_synic_message_page =
> (void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
> - if (!hv_cpu->synic_message_page)
> + if (!hv_cpu->hyp_synic_message_page)
> pr_err("Fail to map synic message page.\n");
> } else {
> - simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
> + simp.base_simp_gpa = virt_to_phys(hv_cpu-
> >hyp_synic_message_page)
> >> HV_HYP_PAGE_SHIFT;
> }
>
> @@ -295,12 +295,12 @@ void hv_synic_enable_regs(unsigned int cpu)
> /* Mask out vTOM bit. ioremap_cache() maps decrypted */
> u64 base = (siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT) &
> ~ms_hyperv.shared_gpa_boundary;
> - hv_cpu->synic_event_page =
> + hv_cpu->hyp_synic_event_page =
> (void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
> - if (!hv_cpu->synic_event_page)
> + if (!hv_cpu->hyp_synic_event_page)
> pr_err("Fail to map synic event page.\n");
> } else {
> - siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
> + siefp.base_siefp_gpa = virt_to_phys(hv_cpu->hyp_synic_event_page)
> >> HV_HYP_PAGE_SHIFT;
> }
>
> @@ -358,8 +358,8 @@ void hv_synic_disable_regs(unsigned int cpu)
> */
> simp.simp_enabled = 0;
> if (ms_hyperv.paravisor_present || hv_root_partition()) {
> - iounmap(hv_cpu->synic_message_page);
> - hv_cpu->synic_message_page = NULL;
> + iounmap(hv_cpu->hyp_synic_message_page);
> + hv_cpu->hyp_synic_message_page = NULL;
> } else {
> simp.base_simp_gpa = 0;
> }
> @@ -370,8 +370,8 @@ void hv_synic_disable_regs(unsigned int cpu)
> siefp.siefp_enabled = 0;
>
> if (ms_hyperv.paravisor_present || hv_root_partition()) {
> - iounmap(hv_cpu->synic_event_page);
> - hv_cpu->synic_event_page = NULL;
> + iounmap(hv_cpu->hyp_synic_event_page);
> + hv_cpu->hyp_synic_event_page = NULL;
> } else {
> siefp.base_siefp_gpa = 0;
> }
> @@ -401,7 +401,7 @@ static bool hv_synic_event_pending(void)
> {
> struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
> union hv_synic_event_flags *event =
> - (union hv_synic_event_flags *)hv_cpu->synic_event_page +
> VMBUS_MESSAGE_SINT;
> + (union hv_synic_event_flags *)hv_cpu->hyp_synic_event_page +
> VMBUS_MESSAGE_SINT;
> unsigned long *recv_int_page = event->flags; /* assumes VMBus version >=
> VERSION_WIN8 */
> bool pending;
> u32 relid;
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 0b450e53161e..fc3cdb26ff1a 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -120,8 +120,8 @@ enum {
> * Per cpu state for channel handling
> */
> struct hv_per_cpu_context {
> - void *synic_message_page;
> - void *synic_event_page;
> + void *hyp_synic_message_page;
> + void *hyp_synic_event_page;
>
> /*
> * The page is only used in hv_post_message() for a TDX VM (with the
> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
> index e3931b0f1269..db6b42db2fdc 100644
> --- a/drivers/hv/mshv_root.h
> +++ b/drivers/hv/mshv_root.h
> @@ -169,7 +169,7 @@ struct mshv_girq_routing_table {
> };
>
> struct hv_synic_pages {
> - struct hv_message_page *synic_message_page;
> + struct hv_message_page *hyp_synic_message_page;
> struct hv_synic_event_flags_page *synic_event_flags_page;
> struct hv_synic_event_ring_page *synic_event_ring_page;
> };
> diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c
> index e6b6381b7c36..f8b0337cdc82 100644
> --- a/drivers/hv/mshv_synic.c
> +++ b/drivers/hv/mshv_synic.c
> @@ -394,7 +394,7 @@ mshv_intercept_isr(struct hv_message *msg)
> void mshv_isr(void)
> {
> struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
> - struct hv_message_page **msg_page = &spages->synic_message_page;
> + struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
> struct hv_message *msg;
> bool handled;
>
> @@ -456,7 +456,7 @@ int mshv_synic_init(unsigned int cpu)
> #endif
> union hv_synic_scontrol sctrl;
> struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
> - struct hv_message_page **msg_page = &spages->synic_message_page;
> + struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
> struct hv_synic_event_flags_page **event_flags_page =
> &spages->synic_event_flags_page;
> struct hv_synic_event_ring_page **event_ring_page =
> @@ -550,7 +550,7 @@ int mshv_synic_cleanup(unsigned int cpu)
> union hv_synic_sirbp sirbp;
> union hv_synic_scontrol sctrl;
> struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
> - struct hv_message_page **msg_page = &spages->synic_message_page;
> + struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
> struct hv_synic_event_flags_page **event_flags_page =
> &spages->synic_event_flags_page;
> struct hv_synic_event_ring_page **event_ring_page =
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 698c86c4ef03..72940a64b0b6 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1060,7 +1060,7 @@ static void vmbus_onmessage_work(struct work_struct
> *work)
> void vmbus_on_msg_dpc(unsigned long data)
> {
> struct hv_per_cpu_context *hv_cpu = (void *)data;
> - void *page_addr = hv_cpu->synic_message_page;
> + void *page_addr = hv_cpu->hyp_synic_message_page;
> struct hv_message msg_copy, *msg = (struct hv_message *)page_addr +
> VMBUS_MESSAGE_SINT;
> struct vmbus_channel_message_header *hdr;
> @@ -1244,7 +1244,7 @@ static void vmbus_chan_sched(struct hv_per_cpu_context
> *hv_cpu)
> * The event page can be directly checked to get the id of
> * the channel that has the interrupt pending.
> */
> - void *page_addr = hv_cpu->synic_event_page;
> + void *page_addr = hv_cpu->hyp_synic_event_page;
> union hv_synic_event_flags *event
> = (union hv_synic_event_flags *)page_addr +
> VMBUS_MESSAGE_SINT;
> @@ -1327,7 +1327,7 @@ static void vmbus_isr(void)
>
> vmbus_chan_sched(hv_cpu);
>
> - page_addr = hv_cpu->synic_message_page;
> + page_addr = hv_cpu->hyp_synic_message_page;
> msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
>
> /* Check if there are actual msgs to be processed */
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 04/16] arch/x86: mshyperv: Trap on access for some synthetic MSRs
From: Michael Kelley @ 2025-07-22 17:43 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-5-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> hv_set_non_nested_msr() has special handling for SINT MSRs
> when a paravisor is present. In addition to updating the MSR on the
> host, the mirror MSR in the paravisor is updated, including with the
> proxy bit. But with Confidential VMBus, the proxy bit must not be
> used, so add a special case to skip it.
>
> Update the hv_set_non_nested_msr() function as well as
> vmbus_signal_eom() to trap on access for some synthetic MSRs.
This paragraph looks like a leftover from the previous version of
the commit message. vmbus_signal_eom() is not touched in this
patch.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
> ---
> arch/x86/kernel/cpu/mshyperv.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 07c60231d0d8..6c5a0a779c02 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -28,6 +28,7 @@
> #include <asm/apic.h>
> #include <asm/timer.h>
> #include <asm/reboot.h>
> +#include <asm/msr.h>
> #include <asm/nmi.h>
> #include <clocksource/hyperv_timer.h>
> #include <asm/msr.h>
> @@ -79,13 +80,21 @@ EXPORT_SYMBOL_GPL(hv_get_non_nested_msr);
> void hv_set_non_nested_msr(unsigned int reg, u64 value)
> {
> if (hv_is_synic_msr(reg) && ms_hyperv.paravisor_present) {
> + /* The hypervisor will get the intercept. */
> hv_ivm_msr_write(reg, value);
>
> - /* Write proxy bit via wrmsl instruction */
> - if (hv_is_sint_msr(reg))
> - wrmsrq(reg, value | 1 << 20);
> + if (hv_is_sint_msr(reg)) {
> + /*
> + * Write proxy bit in the case of non-confidential VMBus.
> + * Using wrmsrq instruction so the following goes to the paravisor.
> + */
> + u32 proxy = vmbus_is_confidential() ? 0 : 1;
The kernel test robot is rightly complaining about vmbus_is_confidential()
being used here. vmbus_is_confidential() comes from vmbus_drv.c, which
is built as a module when CONFIG_HYPERV=m. But this code is always
built-in, and built-in code can't directly refer to functions in a module.
Logically, the layering is wrong because vmbus_is_confidential() is
obviously a VMBus concept, while mshyperv.c only deals with Hyper-V
and knows nothing about VMBus. Your v3 patch series has the same
problem, but evidently the kernel test robot didn't notice the issue,
and I didn't notice it either my v3 review.
The best solution is probably to define a 32-bit "proxy bit" value here
in mshyperv.c. hv_set_non_nested_msr() would always OR in that
value before the call to native_wrmsrq() below. Wherever VMBus code
changes the value of is_confidential, it must also call an EXPORTed
function here in mshyperv.c to set or clear the value of "proxy bit".
Overall, it's a bit messy, but I don't see a better solution.
> +
> + value |= (proxy << 20);
> + native_wrmsrq(reg, value);
> + }
> } else {
> - wrmsrq(reg, value);
> + native_wrmsrq(reg, value);
> }
> }
> EXPORT_SYMBOL_GPL(hv_set_non_nested_msr);
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 03/16] arch: hyperv: Get/set SynIC synth.registers via paravisor
From: Michael Kelley @ 2025-07-22 17:43 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-4-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The existing Hyper-V wrappers for getting and setting MSRs are
> hv_get/set_msr(). Via hv_get/set_non_nested_msr(), they detect
> when running in a CoCo VM with a paravisor, and use the TDX or
> SNP guest-host communication protocol to bypass the paravisor
> and go directly to the host hypervisor for SynIC MSRs. The "set"
> function also implements the required special handling for the
> SINT MSRs.
>
> But in some Confidential VMBus cases, the guest wants to talk only
> with the paravisor. To accomplish this, provide new functions for
> accessing SynICs that always do direct accesses (i.e., not via
> TDX or SNP GHCB), which will go to the paravisor. The mirroring
> of the existing "set" function is also not needed. These functions
> should be used only in the specific Confidential VMBus cases that
> require them.
>
> Provide functions that allow manipulating the SynIC registers
> through the paravisor.
This last paragraph seems to be a leftover from a previous
version of the commit message. I think it can be deleted since
the second paragraph now covers the topic.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
> ---
> arch/x86/kernel/cpu/mshyperv.c | 39 ++++++++++++++++++
> drivers/hv/hv_common.c | 13 ++++++
> include/asm-generic/mshyperv.h | 75 ++++++++++++++++++----------------
> 3 files changed, 92 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index c78f860419d6..07c60231d0d8 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -90,6 +90,45 @@ void hv_set_non_nested_msr(unsigned int reg, u64 value)
> }
> EXPORT_SYMBOL_GPL(hv_set_non_nested_msr);
>
> +/*
> + * Attempt to get the SynIC register value from the paravisor.
> + *
> + * Not all paravisors support reading SynIC registers, so this function
> + * may fail. The register for the SynIC of the running CPU is accessed.
> + *
> + * Writes the SynIC register value into the memory pointed by val,
> + * and ~0ULL is on failure.
> + *
> + * Returns -ENODEV if the MSR is not a SynIC register, or another error
> + * code if getting the MSR fails (meaning the paravisor doesn't support
> + * relaying VMBus communucations).
> + */
> +int hv_para_get_synic_register(unsigned int reg, u64 *val)
> +{
> + if (!hv_is_synic_msr(reg))
> + return -ENODEV;
> + return native_read_msr_safe(reg, val);
> +}
> +
> +/*
> + * Attempt to set the SynIC register value with the paravisor.
> + *
> + * Not all paravisors support setting SynIC registers, so this function
> + * may fail. The register for the SynIC of the running CPU is accessed.
> + *
> + * Sets the register to the value supplied.
> + *
> + * Returns: -ENODEV if the MSR is not a SynIC register, or another error
> + * code if writing to the MSR fails (meaning the paravisor doesn't support
> + * relaying VMBus communucations).
> + */
> +int hv_para_set_synic_register(unsigned int reg, u64 val)
> +{
> + if (!hv_is_synic_msr(reg))
> + return -ENODEV;
> + return native_write_msr_safe(reg, val);
> +}
> +
> u64 hv_get_msr(unsigned int reg)
> {
> if (hv_nested)
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 49898d10faff..a179ea482cb1 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -716,6 +716,19 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
> }
> EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
>
> +int __weak hv_para_get_synic_register(unsigned int reg, u64 *val)
> +{
> + *val = ~0ULL;
> + return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(hv_para_get_synic_register);
> +
> +int __weak hv_para_set_synic_register(unsigned int reg, u64 val)
> +{
> + return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(hv_para_set_synic_register);
> +
> void hv_identify_partition_type(void)
> {
> /* Assume guest role */
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 9722934a8332..9447558f425b 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -162,41 +162,6 @@ static inline u64 hv_generate_guest_id(u64 kernel_version)
> return guest_id;
> }
>
> -/* Free the message slot and signal end-of-message if required */
> -static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
> -{
> - /*
> - * On crash we're reading some other CPU's message page and we need
> - * to be careful: this other CPU may already had cleared the header
> - * and the host may already had delivered some other message there.
> - * In case we blindly write msg->header.message_type we're going
> - * to lose it. We can still lose a message of the same type but
> - * we count on the fact that there can only be one
> - * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages
> - * on crash.
> - */
> - if (cmpxchg(&msg->header.message_type, old_msg_type,
> - HVMSG_NONE) != old_msg_type)
> - return;
> -
> - /*
> - * The cmxchg() above does an implicit memory barrier to
> - * ensure the write to MessageType (ie set to
> - * HVMSG_NONE) happens before we read the
> - * MessagePending and EOMing. Otherwise, the EOMing
> - * will not deliver any more messages since there is
> - * no empty slot
> - */
> - if (msg->header.message_flags.msg_pending) {
> - /*
> - * This will cause message queue rescan to
> - * possibly deliver another msg from the
> - * hypervisor
> - */
> - hv_set_msr(HV_MSR_EOM, 0);
> - }
> -}
> -
> int hv_get_hypervisor_version(union hv_hypervisor_version_info *info);
>
> void hv_setup_vmbus_handler(void (*handler)(void));
> @@ -333,6 +298,8 @@ bool hv_is_isolation_supported(void);
> bool hv_isolation_type_snp(void);
> u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
> u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
> +int hv_para_get_synic_register(unsigned int reg, u64 *val);
> +int hv_para_set_synic_register(unsigned int reg, u64 val);
> void hyperv_cleanup(void);
> bool hv_query_ext_cap(u64 cap_query);
> void hv_setup_dma_ops(struct device *dev, bool coherent);
> @@ -375,6 +342,44 @@ static inline int hv_call_create_vp(int node, u64 partition_id,
> u32 vp_index, u3
> #endif /* CONFIG_MSHV_ROOT */
> bool vmbus_is_confidential(void);
>
> +/* Free the message slot and signal end-of-message if required */
> +static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
> +{
> + /*
> + * On crash we're reading some other CPU's message page and we need
> + * to be careful: this other CPU may already had cleared the header
> + * and the host may already had delivered some other message there.
> + * In case we blindly write msg->header.message_type we're going
> + * to lose it. We can still lose a message of the same type but
> + * we count on the fact that there can only be one
> + * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages
> + * on crash.
> + */
> + if (cmpxchg(&msg->header.message_type, old_msg_type,
> + HVMSG_NONE) != old_msg_type)
> + return;
> +
> + /*
> + * The cmxchg() above does an implicit memory barrier to
> + * ensure the write to MessageType (ie set to
> + * HVMSG_NONE) happens before we read the
> + * MessagePending and EOMing. Otherwise, the EOMing
> + * will not deliver any more messages since there is
> + * no empty slot
> + */
> + if (msg->header.message_flags.msg_pending) {
> + /*
> + * This will cause message queue rescan to
> + * possibly deliver another msg from the
> + * hypervisor
> + */
> + if (vmbus_is_confidential())
> + hv_para_set_synic_register(HV_MSR_EOM, 0);
As reported by the kernel test robot, this function call is generating an
error because there's no declaration for hv_para_set_synic_register()
when built with !CONFIG_HYPERV.
One solution is to add a stub higher up in this source code file in
the existing !CONFIG_HYPERV section.
But a better solution might be move vmbus_signal_eom() out of this
file entirely and put it in drivers/hv/hyperv_vmbus.h. Then no stub
for !CONFIG_HYPERV is needed. vmbus_signal_eom() is very much
a VMBus function, and it's only called from vmbus_wait_for_unload(),
__vmbus_on_msg_dpc(), and vmbus_message_sched().
The file asm-generic/mshyperv.h should be focused on the Hyper-V
interface, not on VMBus, so it's not clear to me why vmbus_signal_eom()
is in asm-generic/mshyperv.h in the first place. There's no reason to expose
vmbus_signal_eom() to code that needs definitions related to Hyper-V,
such as the x86 MTRR code or the Hyper-V emulation code in KVM
(which is where the kernel test robot detected the error). Note that
drivers/hv/hyperv_vmbus.h will need to add #include <asm/mshyperv.h>
in order for the move to work.
I've tested build with CONFIG_HYPERV and !CONFIG_HYPERV on
x86 and on arm64, and the proposed move seems to work OK.
Sorry my suggestion in v3 of your patch set to handle HV_MSR_EOM
here in vmbus_signal_eom() turned out to be more complicated than
I originally contemplated. :-(
> + else
> + hv_set_msr(HV_MSR_EOM, 0);
> + }
> +}
> +
> #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
> u8 __init get_vtl(void);
> #else
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 02/16] drivers: hv: VMBus protocol version 6.0
From: Michael Kelley @ 2025-07-22 17:43 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-3-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> The confidential VMBus is supported starting from the protocol
> version 6.0 onwards.
>
> Update the relevant definitions, and provide a function that returns
> whether VMBus is confidential or not. No functional changes.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> drivers/hv/vmbus_drv.c | 12 ++++++
> include/asm-generic/mshyperv.h | 1 +
> include/linux/hyperv.h | 69 ++++++++++++++++++++++++----------
> 3 files changed, 63 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 33b524b4eb5e..698c86c4ef03 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -56,6 +56,18 @@ static long __percpu *vmbus_evt;
> int vmbus_irq;
> int vmbus_interrupt;
>
> +/*
> + * If the Confidential VMBus is used, the data on the "wire" is not
> + * visible to either the host or the hypervisor.
> + */
> +static bool is_confidential;
> +
> +bool vmbus_is_confidential(void)
> +{
> + return is_confidential;
> +}
> +EXPORT_SYMBOL_GPL(vmbus_is_confidential);
> +
> /*
> * The panic notifier below is responsible solely for unloading the
> * vmbus connection, which is necessary in a panic event.
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index a729b77983fa..9722934a8332 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -373,6 +373,7 @@ static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u3
> return -EOPNOTSUPP;
> }
> #endif /* CONFIG_MSHV_ROOT */
> +bool vmbus_is_confidential(void);
>
> #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
> u8 __init get_vtl(void);
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index a59c5c3e95fb..a1820fabbfc0 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -265,16 +265,18 @@ static inline u32 hv_get_avail_to_write_percent(
> * Linux kernel.
> */
>
> -#define VERSION_WS2008 ((0 << 16) | (13))
> -#define VERSION_WIN7 ((1 << 16) | (1))
> -#define VERSION_WIN8 ((2 << 16) | (4))
> -#define VERSION_WIN8_1 ((3 << 16) | (0))
> -#define VERSION_WIN10 ((4 << 16) | (0))
> -#define VERSION_WIN10_V4_1 ((4 << 16) | (1))
> -#define VERSION_WIN10_V5 ((5 << 16) | (0))
> -#define VERSION_WIN10_V5_1 ((5 << 16) | (1))
> -#define VERSION_WIN10_V5_2 ((5 << 16) | (2))
> -#define VERSION_WIN10_V5_3 ((5 << 16) | (3))
> +#define VMBUS_MAKE_VERSION(MAJ, MIN) ((((u32)MAJ) << 16) | (MIN))
> +#define VERSION_WS2008
> VMBUS_MAKE_VERSION(0, 13)
> +#define VERSION_WIN7
> VMBUS_MAKE_VERSION(1, 1)
> +#define VERSION_WIN8
> VMBUS_MAKE_VERSION(2, 4)
> +#define VERSION_WIN8_1
> VMBUS_MAKE_VERSION(3, 0)
> +#define VERSION_WIN10
> VMBUS_MAKE_VERSION(4, 0)
> +#define VERSION_WIN10_V4_1
> VMBUS_MAKE_VERSION(4, 1)
> +#define VERSION_WIN10_V5 VMBUS_MAKE_VERSION(5, 0)
> +#define VERSION_WIN10_V5_1
> VMBUS_MAKE_VERSION(5, 1)
> +#define VERSION_WIN10_V5_2
> VMBUS_MAKE_VERSION(5, 2)
> +#define VERSION_WIN10_V5_3
> VMBUS_MAKE_VERSION(5, 3)
> +#define VERSION_WIN10_V6_0
> VMBUS_MAKE_VERSION(6, 0)
>
> /* Make maximum size of pipe payload of 16K */
> #define MAX_PIPE_DATA_PAYLOAD (sizeof(u8) * 16384)
> @@ -335,14 +337,22 @@ struct vmbus_channel_offer {
> } __packed;
>
> /* Server Flags */
> -#define VMBUS_CHANNEL_ENUMERATE_DEVICE_INTERFACE 1
> -#define VMBUS_CHANNEL_SERVER_SUPPORTS_TRANSFER_PAGES 2
> -#define VMBUS_CHANNEL_SERVER_SUPPORTS_GPADLS 4
> -#define VMBUS_CHANNEL_NAMED_PIPE_MODE 0x10
> -#define VMBUS_CHANNEL_LOOPBACK_OFFER 0x100
> -#define VMBUS_CHANNEL_PARENT_OFFER 0x200
> -#define VMBUS_CHANNEL_REQUEST_MONITORED_NOTIFICATION 0x400
> -#define VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER 0x2000
> +#define VMBUS_CHANNEL_ENUMERATE_DEVICE_INTERFACE 0x0001
> +/*
> + * This flag indicates that the channel is offered by the paravisor, and must
> + * use encrypted memory for the channel ring buffer.
> + */
> +#define VMBUS_CHANNEL_CONFIDENTIAL_RING_BUFFER 0x0002
> +/*
> + * This flag indicates that the channel is offered by the paravisor, and must
> + * use encrypted memory for GPA direct packets and additional GPADLs.
> + */
> +#define VMBUS_CHANNEL_CONFIDENTIAL_EXTERNAL_MEMORY 0x0004
> +#define VMBUS_CHANNEL_NAMED_PIPE_MODE
> 0x0010
> +#define VMBUS_CHANNEL_LOOPBACK_OFFER
> 0x0100
> +#define VMBUS_CHANNEL_PARENT_OFFER
> 0x0200
> +#define VMBUS_CHANNEL_REQUEST_MONITORED_NOTIFICATION 0x0400
> +#define VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER 0x2000
>
> struct vmpacket_descriptor {
> u16 type;
> @@ -621,6 +631,12 @@ struct vmbus_channel_relid_released {
> u32 child_relid;
> } __packed;
>
> +/*
> + * Used by the paravisor only, means that the encrypted ring buffers and
> + * the encrypted external memory are supported
> + */
> +#define VMBUS_FEATURE_FLAG_CONFIDENTIAL_CHANNELS 0x10
> +
> struct vmbus_channel_initiate_contact {
> struct vmbus_channel_message_header header;
> u32 vmbus_version_requested;
> @@ -630,7 +646,8 @@ struct vmbus_channel_initiate_contact {
> struct {
> u8 msg_sint;
> u8 msg_vtl;
> - u8 reserved[6];
> + u8 reserved[2];
> + u32 feature_flags; /* VMBus version 6.0 */
> };
> };
> u64 monitor_page1;
> @@ -1008,6 +1025,10 @@ struct vmbus_channel {
>
> /* boolean to control visibility of sysfs for ring buffer */
> bool ring_sysfs_visible;
> + /* The ring buffer is encrypted */
> + bool co_ring_buffer;
> + /* The external memory is encrypted */
> + bool co_external_memory;
> };
>
> #define lock_requestor(channel, flags) \
> @@ -1032,6 +1053,16 @@ u64 vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
> u64 rqst_addr);
> u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id);
>
> +static inline bool is_co_ring_buffer(const struct vmbus_channel_offer_channel *o)
> +{
> + return !!(o->offer.chn_flags & VMBUS_CHANNEL_CONFIDENTIAL_RING_BUFFER);
> +}
> +
> +static inline bool is_co_external_memory(const struct vmbus_channel_offer_channel *o)
> +{
> + return !!(o->offer.chn_flags & VMBUS_CHANNEL_CONFIDENTIAL_EXTERNAL_MEMORY);
> +}
> +
> static inline bool is_hvsock_offer(const struct vmbus_channel_offer_channel *o)
> {
> return !!(o->offer.chn_flags & VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER);
> --
> 2.43.0
^ permalink raw reply
* RE: [PATCH hyperv-next v4 01/16] Documentation: hyperv: Confidential VMBus
From: Michael Kelley @ 2025-07-22 17:43 UTC (permalink / raw)
To: Roman Kisel, alok.a.tiwari@oracle.com, arnd@arndb.de,
bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
kys@microsoft.com, mingo@redhat.com, rdunlap@infradead.org,
tglx@linutronix.de, Tianyu.Lan@microsoft.com, wei.liu@kernel.org,
linux-arch@vger.kernel.org, linux-coco@lists.linux.dev,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: apais@microsoft.com, benhill@microsoft.com,
bperkins@microsoft.com, sunilmut@microsoft.com
In-Reply-To: <20250714221545.5615-2-romank@linux.microsoft.com>
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, July 14, 2025 3:16 PM
>
> Define what the confidential VMBus is and describe what advantages
> it offers on the capable hardware.
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Overall, this version looks good. I'm good with the overall
characterization of the scenarios where Confidential VMBus is
beneficial, and with the overview of how it works.
I've noted one nit below. But otherwise,
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> ---
> Documentation/virt/hyperv/coco.rst | 140 ++++++++++++++++++++++++++++-
> 1 file changed, 139 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/hyperv/coco.rst b/Documentation/virt/hyperv/coco.rst
> index c15d6fe34b4e..e8515acfe306 100644
> --- a/Documentation/virt/hyperv/coco.rst
> +++ b/Documentation/virt/hyperv/coco.rst
[snip]
> +
> +The data won't ever leave the VM when a device is attached to VTL2, and the
Two things:
1) At face value, saying "the data won't ever leave the VM" is counter to what I/O
is supposed to be doing -- the data leaves the VM to go to the device! I guess the
wording here struck me as funny. :-)
2) Being more precise about "attached to VTL2" would be helpful. This specifically
means a vPCI device assigned to VTL2.
I'd suggest something like:
The data is transferred directly between the VM and a vPCI device (a.k.a. a PCI
pass-thru device) that is directly assigned to VTL2 and that supports encrypted
memory. In such a case, neither the host partition nor the hypervisor has any
access to the data.
You could even include a link to the documentation topic on Hyper-V vPCI devices.
> +device supports encrypted memory. Therefore, neither the host partition nor the
> +hypervisor can access the data being processed at all. The guest needs to
> +establish a VMBus connection only with the paravisor for the channels that
> +process sensitive data, and the paravisor abstracts the details of
> +communicating with the specific devices away providing the guest with the
> +well-established VSP (Virtual Service Provider) interface that has had support
> +in the Hyper-V drivers for a decade.
> +
^ permalink raw reply
* RE: [PATCH v5 2/2] Drivers: hv: Introduce mshv_vtl driver
From: Michael Kelley @ 2025-07-22 17:09 UTC (permalink / raw)
To: Naman Jain, K . Y . Srinivasan, Haiyang Zhang, Wei Liu,
Dexuan Cui
Cc: Roman Kisel, Anirudh Rayabharam, Saurabh Sengar,
Stanislav Kinsburskii, Nuno Das Neves, ALOK TIWARI,
linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org
In-Reply-To: <5bf4e550-34e1-4b6b-8ee2-137681a72d42@linux.microsoft.com>
From: Naman Jain <namjain@linux.microsoft.com> Sent: Tuesday, July 22, 2025 4:09 AM
>
> On 7/18/2025 8:37 PM, Michael Kelley wrote:
> > From: Naman Jain <namjain@linux.microsoft.com> Sent: Thursday, July 17, 2025 9:36 PM
> >>
> >> On 7/9/2025 10:49 PM, Michael Kelley wrote:
> >>> From: Naman Jain <namjain@linux.microsoft.com> Sent: Wednesday, June 11, 2025 12:27 AM
> >
> > [snip]
> >
> >>
> >>> Separately, "allow_bitmap" size is 64K bytes, or 512K bits. Is that the
> >>> correct size? From looking at mshv_vtl_hvcall_is_allowed(), I think this
> >>> bitmap is indexed by the HV call code, which is a 16 bit value. So you
> >>> only need 64K bits, and the size is too big by a factor of 8. In any case,
> >>> it seems like the size should not be expressed in terms of PAGE_SIZE.
> >>
> >> There are HVcall codes which are of type u16. So max(HVcall code) =
> >> 0xffff.
> >>
> >> For every HVcall that needs to be allowed, we are saving HVcall code
> >> info in a bitmap in below fashion:
> >> if x = HVCall code and bitmap is an array of u64, of size
> >> ((0xffff/64=1023) + 1)
> >>
> >> bitmap[x / 64] = (u64)1 << (x%64);
> >>
> >> Later on in mshv_vtl_hvcall_is_allowed(), we calculate the array index
> >> by dividing it by 64, and then see if call_code/64 bit is set.
> >
> > I didn't add comments in mshv_vtl_hvcall_is_allowed(), but that code
> > can be simplified by recognizing that the Linux kernel bitmap utilities
> > can operate on bitmaps that are much larger than just 64 bits. Let's
> > assume that the allow_bitmap field in struct mshv_vtl_hvcall_fds has
> > 64K bits, regardless of whether it is declared as an array of u64,
> > an array of u16, or an array of u8. Then mshv_vtl_hvcall_is_allowed()
> > can be implemented as a single line:
> >
> > return test_bit(call_code, fd->allow_bitmap);
> >
> > There's no need to figure out which array element contains the bit,
> > or to construct a mask to select that particular bit in the array element.
> > And since call_code is a u16, test_bit won't access outside the allocated
> > 64K bits.
> >
>
> I understood it now. This works and is much better. Will incorporate it
> in next patch.
>
> >>
> >> Coming to size of allow_bitmap[], it is independent of PAGE_SIZE, and
> >> can be safely initialized to 1024 (reducing by a factor of 8).
> >> bitmap_size's maximum value is going to be 1024 in current
> >> implementation, picking u64 was not mandatory, u16 will also work. Also,
> >> item_index is also u16, so I should make bitmap_size as u16.
> >
> > The key question for me is whether bitmap_size describes the number
> > of bits in allow_bitmap, or whether it describes the number of array
> > elements in the declared allow_bitmap array. It's more typical to
> > describe a bitmap size as the number of bits. Then the value is
> > independent of the array element size, as the array element size
> > usually doesn't really matter anyway if using the Linux kernel's
> > bitmap utilities. The array element size only matters in allocating
> > the correct amount of space is for whatever number of bits are
> > needed in the bitmap.
> >
>
> I tried to put your suggestions in code. Please let me know if below
> works. I tested this and it works. Just that, I am a little hesitant in
> changing things on Userspace side of it, which passes these parameters
> in IOCTL. This way, userspace remains the same, the confusion of names
> may go away, and the code becomes simpler.
Yes, I suspected there might be constraints due to not wanting
to disturb existing user space code.
>
> --- a/include/uapi/linux/mshv.h
> +++ b/include/uapi/linux/mshv.h
> @@ -332,7 +332,7 @@ struct mshv_vtl_set_poll_file {
> };
>
> struct mshv_vtl_hvcall_setup {
> - __u64 bitmap_size;
> + __u64 bitmap_array_size;
> __u64 allow_bitmap_ptr; /* pointer to __u64 */
> };
>
>
> --- a/drivers/hv/mshv_vtl_main.c
> +++ b/drivers/hv/mshv_vtl_main.c
> @@ -52,10 +52,12 @@ static bool has_message;
> static struct eventfd_ctx *flag_eventfds[HV_EVENT_FLAGS_COUNT];
> static DEFINE_MUTEX(flag_lock);
> static bool __read_mostly mshv_has_reg_page;
> -#define MAX_BITMAP_SIZE 1024
> +
> +/* hvcall code is of type u16, allocate a bitmap of size (1 << 16) to accomodate it */
s/accomodate/accommodate/
> +#define MAX_BITMAP_SIZE (1 << 16)
>
> struct mshv_vtl_hvcall_fd {
> - u64 allow_bitmap[MAX_BITMAP_SIZE];
> + u64 allow_bitmap[MAX_BITMAP_SIZE / 64];
OK, this seems like a reasonable approach to get the correct
number of bits.
> bool allow_map_initialized;
> /*
> * Used to protect hvcall setup in IOCTLs
>
> @@ -1204,12 +1207,12 @@ static int mshv_vtl_hvcall_do_setup(struct mshv_vtl_hvcall_fd *fd,
> sizeof(struct mshv_vtl_hvcall_setup))) {
> return -EFAULT;
> }
> - if (hvcall_setup.bitmap_size > ARRAY_SIZE(fd->allow_bitmap)) {
> + if (hvcall_setup.bitmap_array_size > ARRAY_SIZE(fd->allow_bitmap)) {
> return -EINVAL;
> }
> if (copy_from_user(&fd->allow_bitmap,
> (void __user *)hvcall_setup.allow_bitmap_ptr,
> - hvcall_setup.bitmap_size)) {
> + hvcall_setup.bitmap_array_size)) {
This still doesn't work. copy_from_user() expects a byte count as its
3rd argument. If we have 64K bits in the bitmap, that means 8K bytes,
and 1K for bitmap_array_size. So the value of the 3rd argument
here is 1K, and you'll be copying 1K bytes when you want to be
copying 8K bytes. The 3rd argument needs to be:
hv_call_setup.bitmap_array_size * sizeof(u64)
It's a bit messy to have to add this multiply, and in the bigger
picture it might be cleaner to have the bitmap_array be
declared in units of u8 instead of u64, but that would affect
user space in a way that you probably want to avoid.
Have you checked that user space is passing in the correct values
to the ioctl? If the kernel side code is wrong, user space might be
wrong as well. And if user space is wrong, then you might have
the flexibility to change everything to use u8 instead of u64.
> return -EFAULT;
> }
>
> @@ -1221,11 +1224,7 @@ static int mshv_vtl_hvcall_do_setup(struct mshv_vtl_hvcall_fd *fd,
>
> static bool mshv_vtl_hvcall_is_allowed(struct mshv_vtl_hvcall_fd *fd, u16 call_code)
> {
> - u8 bits_per_item = 8 * sizeof(fd->allow_bitmap[0]);
> - u16 item_index = call_code / bits_per_item;
> - u64 mask = 1ULL << (call_code % bits_per_item);
> -
> - return fd->allow_bitmap[item_index] & mask;
> + return test_bit(call_code, (unsigned long *)fd->allow_bitmap);
> }
Yes, the rest of this looks good.
Michael
^ permalink raw reply
* RE: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in default_device_exit_net()
From: Haiyang Zhang @ 2025-07-22 16:20 UTC (permalink / raw)
To: Kuniyuki Iwashima, Jakub Kicinski
Cc: Haiyang Zhang, linux-hyperv@vger.kernel.org,
netdev@vger.kernel.org, KY Srinivasan, wei.liu@kernel.org,
edumazet@google.com, pabeni@redhat.com, horms@kernel.org,
davem@davemloft.net, sdf@fomichev.me, ahmed.zaki@intel.com,
aleksander.lobakin@intel.com, linux-kernel@vger.kernel.org
In-Reply-To: <CAAVpQUC_sH2UDdf0e5c=iPFU5EcaB7YeN=__2j6w_h6_pe8m_g@mail.gmail.com>
> -----Original Message-----
> From: Kuniyuki Iwashima <kuniyu@google.com>
> Sent: Saturday, July 19, 2025 4:48 PM
> To: Jakub Kicinski <kuba@kernel.org>
> Cc: Haiyang Zhang <haiyangz@linux.microsoft.com>; linux-
> hyperv@vger.kernel.org; netdev@vger.kernel.org; Haiyang Zhang
> <haiyangz@microsoft.com>; KY Srinivasan <kys@microsoft.com>;
> wei.liu@kernel.org; edumazet@google.com; pabeni@redhat.com;
> horms@kernel.org; davem@davemloft.net; sdf@fomichev.me;
> ahmed.zaki@intel.com; aleksander.lobakin@intel.com; linux-
> kernel@vger.kernel.org
> Subject: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in
> default_device_exit_net()
>
> [You don't often get email from kuniyu@google.com. Learn why this is
> important at https://aka.ms/LearnAboutSenderIdentification ]
>
> On Fri, Jul 18, 2025 at 4:37 PM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > On Fri, 18 Jul 2025 13:20:14 -0700 Haiyang Zhang wrote:
> > > The loop in default_device_exit_net() won't be able to properly detect
> the
> > > head then stop, and will hit NULL pointer, when a driver, like
> hv_netvsc,
> > > automatically moves the slave device together with the master device.
> > >
> > > To fix this, add a helper function to return the first migratable
> netdev
> > > correctly, no matter one or two devices were removed from this net's
> list
> > > in the last iteration.
> >
> > FTR I think that what the driver is trying to do is way too hacky, and
> > it should be fixed instead. But I defer to Kuniyuki for the final word,
> > maybe this change is useful for other reasons..
>
> I agree that it should be fixed on the driver side. I don't
> think of a good reason for the change.
Kuniyuki and Jakub:
Thanks for the reviews. I'm working on a patch that will fix the driver side.
- Haiyang
^ permalink raw reply
page: next (older) | prev (newer) | latest
- recent:[subjects (threaded)|topics (new)|topics (active)]
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox