Re: [patch] x86/realmode: Make stack lock work in trampoline_compat()

[Kirill A. Shutemov]

On Tue, May 30, 2023 at 12:46:22PM +0200, Thomas Gleixner wrote:
> The stack locking and stack assignment macro LOAD_REALMODE_ESP fails to
> work when invoked from the 64bit trampoline entry point:
> 
> trampoline_start64
>   trampoline_compat
>     LOAD_REALMODE_ESP <- lock
> 
> Accessing tr_lock is only possible from 16bit mode. For the compat entry
> point this needs to be pa_tr_lock so that the required relocation entry is
> generated. Otherwise it locks the non-relocated address which is
> aside of being wrong never cleared in secondary_startup_64() causing all
> but the first CPU to get stuck on the lock.
> 
> Make the macro take an argument lock_pa which defaults to 0 and rename it
> to LOCK_AND_LOAD_REALMODE_ESP to make it clear what this is about.
> 
> Fixes: f6f1ae9128d2 ("x86/smpboot: Implement a bit spinlock to protect the realmode stack")
> Reported-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Tested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov