Re: [PATCHv2, RFC] x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G

[Kirill A. Shutemov]

On Sat, Oct 14, 2017 at 01:19:08PM -0400, Brian Gerst wrote:
> From what we've seen with the TLB flush rework, having potential
> garbage in the page tables that speculative reads can see can cause
> bad things like machine checks.  It would be best to have a second
> temporary page just for the page table (and properly cleared).

Hm. Interesting. Is there a place where I can read more about this?

> The trampoline also needs its own stack, in case the stack pointer was
> above 4G.

You are right, we need new stack. I've missed that.

> That could be at the end of the code page, since you only need 8 bytes.

When I wrote about 8 bytes, I referred the usage of page table, not code.
We use more than 8 bytes of code, but this should enough in the page.

-- 
 Kirill A. Shutemov