linux/arch/x86/hyperv
Michael Kelley d5ace2a776 x86/hyperv: Disable IBT when hypercall page lacks ENDBR instruction
On hardware that supports Indirect Branch Tracking (IBT), Hyper-V VMs
with ConfigVersion 9.3 or later support IBT in the guest. However,
current versions of Hyper-V have a bug in that there's not an ENDBR64
instruction at the beginning of the hypercall page. Since hypercalls are
made with an indirect call to the hypercall page, all hypercall attempts
fail with an exception and Linux panics.

A Hyper-V fix is in progress to add ENDBR64. But guard against the Linux
panic by clearing X86_FEATURE_IBT if the hypercall page doesn't start
with ENDBR. The VM will boot and run without IBT.

If future Linux 32-bit kernels were to support IBT, additional hypercall
page hackery would be needed to make IBT work for such kernels in a
Hyper-V VM.

Cc: stable@vger.kernel.org
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1690001476-98594-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
2023-07-23 23:07:39 +00:00
..
hv_apic.c x86/hyperv: Improve code for referencing hyperv_pcpu_input_arg 2023-06-28 17:53:25 +00:00
hv_init.c x86/hyperv: Disable IBT when hypercall page lacks ENDBR instruction 2023-07-23 23:07:39 +00:00
hv_proc.c drivers: hv: Create a consistent pattern for checking Hyper-V hypercall status 2021-04-21 09:49:19 +00:00
hv_spinlock.c x86/hyperv: Fix unused variable 'msr_val' warning in hv_qlock_wait 2021-03-24 11:31:04 +00:00
hv_vtl.c x86/hyperv/vtl: Add noop for realmode pointers 2023-05-08 16:46:43 +00:00
irqdomain.c genirq: Return a const cpumask from irq_data_get_affinity_mask 2022-07-07 09:38:04 +01:00
ivm.c x86/hyperv: Improve code for referencing hyperv_pcpu_input_arg 2023-06-28 17:53:25 +00:00
Makefile x86/hyperv: VTL support for Hyper-V 2023-04-18 17:29:52 +00:00
mmu.c x86/hyperv: Improve code for referencing hyperv_pcpu_input_arg 2023-06-28 17:53:25 +00:00
nested.c x86/hyperv: Improve code for referencing hyperv_pcpu_input_arg 2023-06-28 17:53:25 +00:00