Re: [Xen-devel] [PATCH v2 4/6] xen/x86: disable global pages for domains with XPTI active

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Mar 02, 2018 at 09:14:01AM +0100, Juergen Gross wrote:
> Instead of flushing the TLB from global pages when switching address
> spaces with XPTI being active just disable global pages via %cr4
> completely when a domain subject to XPTI is active. This avoids the
> need for extra TLB flushes as loading %cr3 will remove all TLB
> entries.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

I think you patch tries to disable PGE wholesale for Xen, but I don't
think this patch catches all of them.

XEN_MINIMAL_CR4 still has PGE in it. EFI path and the stack resyncing
asm in __start_xen are missing. 

You also missed fixing the comment of setting MTRR. It is not a big deal
though.

I have in fact written a small series to make CR4.PGE configurable but
haven't got around to send the patches yet because I didn't think it is
very useful in its own.

Wei.

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