Re: [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR

[Andy Lutomirski]

On 6/10/22 07:35, Kirill A. Shutemov wrote:

> +	/* Update CR3 to get LAM active */
> +	switch_mm(current->mm, current->mm, current);

Can you at least justify this oddity?  When changing an LDT, we use a 
dedicated mechanism.  Is there a significant benefit to abusing 
switch_mm for this?

Also, why can't we enable LAM on a multithreaded process?  We can change 
an LDT, and the code isn't even particularly complicated.