Re: [PATCH v10 33/38] x86/entry: Add fred_entry_from_kvm() for VMX to handle IRQ/NMI

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

On 9/14/23 06:48, Xin Li wrote:
> +       /*
> +        * Don't check the FRED stack level, the call stack leading to this
> +        * helper is effectively constant and shallow (relatively speaking).
It's more that we don't need to protect from reentrancy.  The external 
interrupt uses stack level 0 so no adjustment would be needed anyway, 
and NMI does not use an IST even in the non-FRED case.
> +        * Emulate the FRED-defined redzone and stack alignment.
> +        */
> +       sub $(FRED_CONFIG_REDZONE_AMOUNT << 6), %rsp
> +       and $FRED_STACK_FRAME_RSP_MASK, %rsp