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cceb4e0810
Don't set *this_cpu_ptr(hyperv_pcpu_input_arg) before the function set_memory_decrypted() returns, otherwise we run into this ticky issue: For a fully enlightened TDX/SNP VM, in hv_common_cpu_init(), *this_cpu_ptr(hyperv_pcpu_input_arg) is an encrypted page before the set_memory_decrypted() returns. When such a VM has more than 64 VPs, if the hyperv_pcpu_input_arg is not NULL, hv_common_cpu_init() -> set_memory_decrypted() -> ... -> cpa_flush() -> on_each_cpu() -> ... -> hv_send_ipi_mask() -> ... -> __send_ipi_mask_ex() tries to call hv_do_rep_hypercall() with the hyperv_pcpu_input_arg as the hypercall input page, which must be a decrypted page in such a VM, but the page is still encrypted at this point, and a fatal fault is triggered. Fix the issue by setting *this_cpu_ptr(hyperv_pcpu_input_arg) after set_memory_decrypted(): if the hyperv_pcpu_input_arg is NULL, __send_ipi_mask_ex() returns HV_STATUS_INVALID_PARAMETER immediately, and hv_send_ipi_mask() falls back to orig_apic.send_IPI_mask(), which can use x2apic_send_IPI_all(), which may be slightly slower than the hypercall but still works correctly in such a VM. Reviewed-by: Michael Kelley <mikelley@microsoft.com> Reviewed-by: Tianyu Lan <tiala@microsoft.com> Signed-off-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> Link: https://lore.kernel.org/r/20230824080712.30327-6-decui@microsoft.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.