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

Paolo Bonzini
2023-09-20T17:55:49Z

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