Messages in this thread | | | Date | Wed, 18 Jan 2023 14:46:14 +0300 | From | kirill.shutemov@linux ... | Subject | Re: [PATCH v2 1/7] x86/boot: Remove verify_cpu() from secondary_startup_64() |
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On Wed, Jan 18, 2023 at 10:45:44AM +0100, Peter Zijlstra wrote: > On Mon, Jan 16, 2023 at 03:25:34PM +0100, Peter Zijlstra wrote: > > The boot trampolines from trampoline_64.S have code flow like: > > > > 16bit BIOS SEV-ES 64bit EFI > > > > trampoline_start() sev_es_trampoline_start() trampoline_start_64() > > verify_cpu() | | > > switch_to_protected: <---------------' v > > | pa_trampoline_compat() > > v | > > startup_32() <-----------------------------------------------' > > | > > v > > startup_64() > > | > > v > > tr_start() := head_64.S:secondary_startup_64() > > > > Since AP bringup always goes through the 16bit BIOS path (EFI doesn't > > touch the APs), there is already a verify_cpu() invocation. > > So supposedly TDX/ACPI-6.4 comes in on trampoline_startup64() for APs -- > can any of the TDX capable folks tell me if we need verify_cpu() on > these? > > Aside from checking for LM, it seems to clear XD_DISABLE on Intel and > force enable SSE on AMD/K7. Surely none of that is needed for these > shiny new chips?
TDX has no XD_DISABLE set and it doesn't allow to write to IA32_MISC_ENABLE MSR (triggers #VE), so we should be safe.
-- Kiryl Shutsemau / Kirill A. Shutemov
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