linux-kernel - Re: [PATCH] device-dax: map dax memory as decrypted in CoCo guests

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Message-ID: <CAGdbjmLVFZJq7OJv2OwM3knmwfb-j8nZP7G_ownFA3kd3fYbVA@mail.gmail.com>
Date: Mon, 26 Aug 2024 14:35:24 -0700
From: Kevin Loughlin <kevinloughlin@...gle.com>
To: "Gupta, Pankaj" <pankaj.gupta@....com>
Cc: Dan Williams <dan.j.williams@...el.com>, Vishal Verma <vishal.l.verma@...el.com>, 
	Dave Jiang <dave.jiang@...el.com>, nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org, 
	linux-kernel@...r.kernel.org, changyuanl@...gle.com, pgonda@...gle.com, 
	sidtelang@...gle.com, tytso@....edu, pasha.tatashin@...een.com, 
	thomas.lendacky@....com
Subject: Re: [PATCH] device-dax: map dax memory as decrypted in CoCo guests

> How can I test this? Can I test it with virtio-pmem device?

Correct. Assuming the CoCo guest accesses some virtio-pmem device in
devdax mode, mmapping() this virtio-pmem device's memory region
results in the guest and host reading the same (plaintext) values from
the region.



>
> Thanks,
> Pankaj
> >
> > Signed-off-by: Kevin Loughlin <kevinloughlin@...gle.co > ---
> >   drivers/dax/device.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/dax/device.c b/drivers/dax/device.c
> > index 2051e4f73c8a..a284442d7ecc 100644
> > --- a/drivers/dax/device.c
> > +++ b/drivers/dax/device.c
> > @@ -11,6 +11,7 @@
> >   #include <linux/fs.h>
> >   #include <linux/mm.h>
> >   #include <linux/mman.h>
> > +#include <linux/cc_platform.h>
> >   #include "dax-private.h"
> >   #include "bus.h"
> >
> > @@ -303,6 +304,8 @@ static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
> >
> >       vma->vm_ops = &dax_vm_ops;
> >       vm_flags_set(vma, VM_HUGEPAGE);
> > +     if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
> > +             vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
> >       return 0;
> >   }
> >
>