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3645eb7e39
FRED-enabled SEV-(ES,SNP) guests fail to boot due to the following issues
in the early boot sequence:
* FRED does not have a #VC exception handler in the dispatch logic
* Early FRED #VC exceptions attempt to use uninitialized per-CPU GHCBs
instead of boot_ghcb
Add X86_TRAP_VC case to fred_hwexc() with a new exc_vmm_communication()
function that provides the unified entry point FRED requires, dispatching
to existing user/kernel handlers based on privilege level. The function is
already declared via DECLARE_IDTENTRY_VC().
Fix early GHCB access by falling back to boot_ghcb in
__sev_{get,put}_ghcb() when per-CPU GHCBs are not yet initialized.
Fixes: 14619d912b ("x86/fred: FRED entry/exit and dispatch code")
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@kernel.org> # 6.12+
Link: https://patch.msgid.link/20260318075654.1792916-4-nikunj@amd.com