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linux/arch/x86/hyperv
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Michael Kelley 73626b70b3 x86/hyperv: Disable IBT when hypercall page lacks ENDBR instruction 
commit d5ace2a776 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-08-11 12:14:21 +02:00
..
hv_apic.c x86/hyperv: Add callback filter to cpumask_to_vpset() 2023-04-17 19:19:05 +00:00
hv_init.c x86/hyperv: Disable IBT when hypercall page lacks ENDBR instruction 2023-08-11 12:14:21 +02:00
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: Set MTRR state when running as SEV-SNP Hyper-V guest 2023-07-19 16:35:18 +02:00
Makefile x86/hyperv: VTL support for Hyper-V 2023-04-18 17:29:52 +00:00
mmu.c x86/hyperv: Exclude lazy TLB mode CPUs from enlightened TLB flushes 2023-04-17 19:19:05 +00:00
nested.c drivers: hv: Create a consistent pattern for checking Hyper-V hypercall status 2021-04-21 09:49:19 +00:00