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Date:   Thu, 8 Sep 2022 06:35:12 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Davidlohr Bueso <dave@stgolabs.net>, x86@kernel.org,
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Subject: Re: [PATCH -next] memregion: Add arch_flush_memregion() interface
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On Wed, Sep 07, 2022 at 09:52:17AM -0700, Dan Williams wrote:
> To be clear nfit stuff and CXL does run in guests, but they do not
> support secure-erase in a guest.
> 
> However, the QEMU CXL enabling is building the ability to do *guest
> physical* address space management, but in that case the driver can be
> paravirtualized to realize that it is not managing host-physical address
> space and does not need to flush caches. That will need some indicator
> to differentiate virtual CXL memory expanders from assigned devices.

Sounds to me like that check should be improved later to ask
whether the kernel is managing host-physical address space, maybe
arch_flush_memregion() should check whether the address it is supposed
to flush is host-physical and exit early if not...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette