kernel/linux.git/include/linux/hyperv.h, branch v5.10.257

Drivers: hv: vmbus: Add utility function for querying ring size

2025-07-17T16:27:40+00:00

[ Upstream commit e8c4bd6c6e6b7e7b416c42806981c2a81370001e ] Add a function to query for the preferred ring buffer size of VMBus device. This will allow the drivers (eg. UIO) to allocate the most optimized ring buffer size for devices. Signed-off-by: Saurabh Sengar Reviewed-by: Long Li Link: https://lore.kernel.org/r/1711788723-8593-2-git-send-email-ssengar@linux.microsoft.com Signed-off-by: Greg Kroah-Hartman Stable-dep-of: 0315fef2aff9 ("uio_hv_generic: Align ring size to system page") Signed-off-by: Sasha Levin

Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet

2025-01-09T12:24:54+00:00

commit 07a756a49f4b4290b49ea46e089cbe6f79ff8d26 upstream. If the KVP (or VSS) daemon starts before the VMBus channel's ringbuffer is fully initialized, we can hit the panic below: hv_utils: Registering HyperV Utility Driver hv_vmbus: registering driver hv_utils ... BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 44 UID: 0 PID: 2552 Comm: hv_kvp_daemon Tainted: G E 6.11.0-rc3+ #1 RIP: 0010:hv_pkt_iter_first+0x12/0xd0 Call Trace: ... vmbus_recvpacket hv_kvp_onchannelcallback vmbus_on_event tasklet_action_common tasklet_action handle_softirqs irq_exit_rcu sysvec_hyperv_stimer0 asm_sysvec_hyperv_stimer0 ... kvp_register_done hvt_op_read vfs_read ksys_read __x64_sys_read This can happen because the KVP/VSS channel callback can be invoked even before the channel is fully opened: 1) as soon as hv_kvp_init() -> hvutil_transport_init() creates /dev/vmbus/hv_kvp, the kvp daemon can open the device file immediately and register itself to the driver by writing a message KVP_OP_REGISTER1 to the file (which is handled by kvp_on_msg() ->kvp_handle_handshake()) and reading the file for the driver's response, which is handled by hvt_op_read(), which calls hvt->on_read(), i.e. kvp_register_done(). 2) the problem with kvp_register_done() is that it can cause the channel callback to be called even before the channel is fully opened, and when the channel callback is starting to run, util_probe()-> vmbus_open() may have not initialized the ringbuffer yet, so the callback can hit the panic of NULL pointer dereference. To reproduce the panic consistently, we can add a "ssleep(10)" for KVP in __vmbus_open(), just before the first hv_ringbuffer_init(), and then we unload and reload the driver hv_utils, and run the daemon manually within the 10 seconds. Fix the panic by reordering the steps in util_probe() so the char dev entry used by the KVP or VSS daemon is not created until after vmbus_open() has completed. This reordering prevents the race condition from happening. Reported-by: Dexuan Cui Fixes: e0fa3e5e7df6 ("Drivers: hv: utils: fix a race on userspace daemons registration") Cc: stable@vger.kernel.org Signed-off-by: Michael Kelley Acked-by: Wei Liu Link: https://lore.kernel.org/r/20241106154247.2271-3-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20241106154247.2271-3-mhklinux@outlook.com> Signed-off-by: Greg Kroah-Hartman

Drivers: hv: vmbus: Calculate ring buffer size for more efficient use of memory

2024-04-13T10:58:48+00:00

commit b8209544296edbd1af186e2ea9c648642c37b18c upstream. The VMBUS_RING_SIZE macro adds space for a ring buffer header to the requested ring buffer size. The header size is always 1 page, and so its size varies based on the PAGE_SIZE for which the kernel is built. If the requested ring buffer size is a large power-of-2 size and the header size is small, the resulting size is inefficient in its use of memory. For example, a 512 Kbyte ring buffer with a 4 Kbyte page size results in a 516 Kbyte allocation, which is rounded to up 1 Mbyte by the memory allocator, and wastes 508 Kbytes of memory. In such situations, the exact size of the ring buffer isn't that important, and it's OK to allocate the 4 Kbyte header at the beginning of the 512 Kbytes, leaving the ring buffer itself with just 508 Kbytes. The memory allocation can be 512 Kbytes instead of 1 Mbyte and nothing is wasted. Update VMBUS_RING_SIZE to implement this approach for "large" ring buffer sizes. "Large" is somewhat arbitrarily defined as 8 times the size of the ring buffer header (which is of size PAGE_SIZE). For example, for 4 Kbyte PAGE_SIZE, ring buffers of 32 Kbytes and larger use the first 4 Kbytes as the ring buffer header. For 64 Kbyte PAGE_SIZE, ring buffers of 512 Kbytes and larger use the first 64 Kbytes as the ring buffer header. In both cases, smaller sizes add space for the header so the ring size isn't reduced too much by using part of the space for the header. For example, with a 64 Kbyte page size, we don't want a 128 Kbyte ring buffer to be reduced to 64 Kbytes by allocating half of the space for the header. In such a case, the memory allocation is less efficient, but it's the best that can be done. While the new algorithm slightly changes the amount of space allocated for ring buffers by drivers that use VMBUS_RING_SIZE, the devices aren't known to be sensitive to small changes in ring buffer size, so there shouldn't be any effect. Fixes: c1135c7fd0e9 ("Drivers: hv: vmbus: Introduce types of GPADL") Fixes: 6941f67ad37d ("hv_netvsc: Calculate correct ring size when PAGE_SIZE is not 4 Kbytes") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218502 Cc: stable@vger.kernel.org Signed-off-by: Michael Kelley Reviewed-by: Saurabh Sengar Reviewed-by: Dexuan Cui Tested-by: Souradeep Chakrabarti Link: https://lore.kernel.org/r/20240229004533.313662-1-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20240229004533.313662-1-mhklinux@outlook.com> Signed-off-by: Greg Kroah-Hartman

hv_netvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening

2024-03-15T14:48:21+00:00

[ Upstream commit 4d18fcc95f50950a99bd940d4e61a983f91d267a ] Currently, pointers to guest memory are passed to Hyper-V as transaction IDs in netvsc. In the face of errors or malicious behavior in Hyper-V, netvsc should not expose or trust the transaction IDs returned by Hyper-V to be valid guest memory addresses. Instead, use small integers generated by vmbus_requestor as requests (transaction) IDs. Signed-off-by: Andres Beltran Co-developed-by: Andrea Parri (Microsoft) Signed-off-by: Andrea Parri (Microsoft) Reviewed-by: Michael Kelley Acked-by: Jakub Kicinski Reviewed-by: Wei Liu Cc: "David S. Miller" Cc: Jakub Kicinski Cc: netdev@vger.kernel.org Link: https://lore.kernel.org/r/20201109100402.8946-4-parri.andrea@gmail.com Signed-off-by: Wei Liu Stable-dep-of: 9cae43da9867 ("hv_netvsc: Register VF in netvsc_probe if NET_DEVICE_REGISTER missed") Signed-off-by: Sasha Levin

Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening

2024-03-15T14:48:21+00:00

[ Upstream commit e8b7db38449ac5b950a3f00519171c4be3e226ff ] Currently, VMbus drivers use pointers into guest memory as request IDs for interactions with Hyper-V. To be more robust in the face of errors or malicious behavior from a compromised Hyper-V, avoid exposing guest memory addresses to Hyper-V. Also avoid Hyper-V giving back a bad request ID that is then treated as the address of a guest data structure with no validation. Instead, encapsulate these memory addresses and provide small integers as request IDs. Signed-off-by: Andres Beltran Co-developed-by: Andrea Parri (Microsoft) Signed-off-by: Andrea Parri (Microsoft) Reviewed-by: Michael Kelley Reviewed-by: Wei Liu Link: https://lore.kernel.org/r/20201109100402.8946-2-parri.andrea@gmail.com Signed-off-by: Wei Liu Stable-dep-of: 9cae43da9867 ("hv_netvsc: Register VF in netvsc_probe if NET_DEVICE_REGISTER missed") Signed-off-by: Sasha Levin

video: hyperv_fb: Avoid taking busy spinlock on panic path

2023-01-14T09:16:13+00:00

[ Upstream commit 1d044ca035dc22df0d3b39e56f2881071d9118bd ] The Hyper-V framebuffer code registers a panic notifier in order to try updating its fbdev if the kernel crashed. The notifier callback is straightforward, but it calls the vmbus_sendpacket() routine eventually, and such function takes a spinlock for the ring buffer operations. Panic path runs in atomic context, with local interrupts and preemption disabled, and all secondary CPUs shutdown. That said, taking a spinlock might cause a lockup if a secondary CPU was disabled with such lock taken. Fix it here by checking if the ring buffer spinlock is busy on Hyper-V framebuffer panic notifier; if so, bail-out avoiding the potential lockup scenario. Cc: Andrea Parri (Microsoft) Cc: Dexuan Cui Cc: Haiyang Zhang Cc: "K. Y. Srinivasan" Cc: Michael Kelley Cc: Stephen Hemminger Cc: Tianyu Lan Cc: Wei Liu Tested-by: Fabio A M Martins Signed-off-by: Guilherme G. Piccoli Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20220819221731.480795-10-gpiccoli@igalia.com Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

hv: hyperv.h: Introduce some hvpfn helper functions

2020-09-28T08:55:13+00:00

When a guest communicate with the hypervisor, it must use HV_HYP_PAGE to calculate PFN, so introduce a few hvpfn helper functions as the counterpart of the page helper functions. This is the preparation for supporting guest whose PAGE_SIZE is not 4k. Signed-off-by: Boqun Feng Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200916034817.30282-7-boqun.feng@gmail.com Signed-off-by: Wei Liu

Drivers: hv: vmbus: Move virt_to_hvpfn() to hyperv header

2020-09-28T08:55:13+00:00

There will be more places other than vmbus where we need to calculate the Hyper-V page PFN from a virtual address, so move virt_to_hvpfn() to hyperv generic header. Signed-off-by: Boqun Feng Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200916034817.30282-6-boqun.feng@gmail.com Signed-off-by: Wei Liu

Drivers: hv: vmbus: Introduce types of GPADL

2020-09-28T08:55:12+00:00

This patch introduces two types of GPADL: HV_GPADL_{BUFFER, RING}. The types of GPADL are purely the concept in the guest, IOW the hypervisor treat them as the same. The reason of introducing the types for GPADL is to support guests whose page size is not 4k (the page size of Hyper-V hypervisor). In these guests, both the headers and the data parts of the ringbuffers need to be aligned to the PAGE_SIZE, because 1) some of the ringbuffers will be mapped into userspace and 2) we use "double mapping" mechanism to support fast wrap-around, and "double mapping" relies on ringbuffers being page-aligned. However, the Hyper-V hypervisor only uses 4k (HV_HYP_PAGE_SIZE) headers. Our solution to this is that we always make the headers of ringbuffers take one guest page and when GPADL is established between the guest and hypervisor, the only first 4k of header is used. To handle this special case, we need the types of GPADL to differ different guest memory usage for GPADL. Type enum is introduced along with several general interfaces to describe the differences between normal buffer GPADL and ringbuffer GPADL. Signed-off-by: Boqun Feng Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200916034817.30282-4-boqun.feng@gmail.com Signed-off-by: Wei Liu

Drivers: hv: vmbus: Remove the lock field from the vmbus_channel struct

2020-06-20T09:16:19+00:00

The spinlock is (now) *not used to protect test-and-set accesses to attributes of the structure or sc_list operations. There is, AFAICT, a distinct lack of {WRITE,READ}_ONCE()s in the handling of channel->state, but the changes below do not seem to make things "worse". ;-) Signed-off-by: Andrea Parri (Microsoft) Link: https://lore.kernel.org/r/20200617164642.37393-9-parri.andrea@gmail.com Reviewed-by: Michael Kelley Signed-off-by: Wei Liu