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From: Cornelia Huck <cohuck@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: brijesh.singh@amd.com, pair@us.ibm.com, dgilbert@redhat.com,
	pasic@linux.ibm.com, qemu-devel@nongnu.org,
	Richard Henderson <richard.henderson@linaro.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	borntraeger@de.ibm.com,
	Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	mst@redhat.com, jun.nakajima@intel.com, thuth@redhat.com,
	pragyansri.pathi@intel.com, kvm@vger.kernel.org,
	Eduardo Habkost <ehabkost@redhat.com>,
	qemu-s390x@nongnu.org, qemu-ppc@nongnu.org,
	frankja@linux.ibm.com, Greg Kurz <groug@kaod.org>,
	mdroth@linux.vnet.ibm.com, berrange@redhat.com,
	andi.kleen@intel.com
Subject: Re: [PATCH v7 03/13] sev: Remove false abstraction of flash encryption
Date: Fri, 15 Jan 2021 13:54:25 +0100	[thread overview]
Message-ID: <20210115135425.7fd94aed.cohuck@redhat.com> (raw)
In-Reply-To: <20210113235811.1909610-4-david@gibson.dropbear.id.au>

On Thu, 14 Jan 2021 10:58:01 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> When AMD's SEV memory encryption is in use, flash memory banks (which are
> initialed by pc_system_flash_map()) need to be encrypted with the guest's
> key, so that the guest can read them.
> 
> That's abstracted via the kvm_memcrypt_encrypt_data() callback in the KVM
> state.. except, that it doesn't really abstract much at all.
> 
> For starters, the only called is in code specific to the 'pc' family of

s/called/call site/

> machine types, so it's obviously specific to those and to x86 to begin
> with.  But it makes a bunch of further assumptions that need not be true
> about an arbitrary confidential guest system based on memory encryption,
> let alone one based on other mechanisms:
> 
>  * it assumes that the flash memory is defined to be encrypted with the
>    guest key, rather than being shared with hypervisor
>  * it assumes that that hypervisor has some mechanism to encrypt data into
>    the guest, even though it can't decrypt it out, since that's the whole
>    point
>  * the interface assumes that this encrypt can be done in place, which
>    implies that the hypervisor can write into a confidential guests's
>    memory, even if what it writes isn't meaningful
> 
> So really, this "abstraction" is actually pretty specific to the way SEV
> works.  So, this patch removes it and instead has the PC flash
> initialization code call into a SEV specific callback.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  accel/kvm/kvm-all.c    | 31 ++-----------------------------
>  accel/kvm/sev-stub.c   |  9 ++-------
>  accel/stubs/kvm-stub.c | 10 ----------
>  hw/i386/pc_sysfw.c     | 17 ++++++-----------
>  include/sysemu/kvm.h   | 16 ----------------
>  include/sysemu/sev.h   |  4 ++--
>  target/i386/sev-stub.c |  5 +++++
>  target/i386/sev.c      | 24 ++++++++++++++----------
>  8 files changed, 31 insertions(+), 85 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>


  reply	other threads:[~2021-01-15 12:56 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-13 23:57 [PATCH v7 00/13] Generalize memory encryption models David Gibson
2021-01-13 23:57 ` [PATCH v7 01/13] qom: Allow optional sugar props David Gibson
2021-01-13 23:58 ` [PATCH v7 02/13] confidential guest support: Introduce new confidential guest support class David Gibson
2021-01-14  9:34   ` Daniel P. Berrangé
2021-01-14 10:42     ` David Gibson
2021-01-18 18:51   ` Dr. David Alan Gilbert
2021-01-21  1:06     ` David Gibson
2021-01-21  9:08       ` Dr. David Alan Gilbert
2021-01-29  2:32         ` David Gibson
2021-01-13 23:58 ` [PATCH v7 03/13] sev: Remove false abstraction of flash encryption David Gibson
2021-01-15 12:54   ` Cornelia Huck [this message]
2021-01-18  2:59     ` David Gibson
2021-01-13 23:58 ` [PATCH v7 04/13] confidential guest support: Move side effect out of machine_set_memory_encryption() David Gibson
2021-01-15 12:56   ` Cornelia Huck
2021-01-13 23:58 ` [PATCH v7 05/13] confidential guest support: Rework the "memory-encryption" property David Gibson
2021-01-15 13:06   ` Cornelia Huck
2021-01-13 23:58 ` [PATCH v7 06/13] sev: Add Error ** to sev_kvm_init() David Gibson
2021-01-13 23:58 ` [PATCH v7 07/13] confidential guest support: Introduce cgs "ready" flag David Gibson
2021-01-14  8:55   ` Greg Kurz
2021-01-15 13:12   ` Cornelia Huck
2021-01-18 19:47   ` Dr. David Alan Gilbert
2021-01-19  8:16     ` Cornelia Huck
2021-02-02  1:41       ` David Gibson
2021-01-13 23:58 ` [PATCH v7 08/13] confidential guest support: Move SEV initialization into arch specific code David Gibson
2021-01-15 13:24   ` Cornelia Huck
2021-01-18  3:03     ` David Gibson
2021-01-18  8:03       ` Cornelia Huck
2021-01-29  3:12         ` David Gibson
2021-01-13 23:58 ` [PATCH v7 09/13] confidential guest support: Update documentation David Gibson
2021-01-14 10:07   ` Greg Kurz
2021-01-15 15:36   ` Cornelia Huck
2021-01-29  2:36     ` David Gibson
2021-01-13 23:58 ` [PATCH v7 10/13] spapr: Add PEF based confidential guest support David Gibson
2021-01-15 15:41   ` Cornelia Huck
2021-01-29  2:43     ` David Gibson
2021-01-13 23:58 ` [PATCH v7 11/13] spapr: PEF: prevent migration David Gibson
2021-01-13 23:58 ` [PATCH v7 12/13] confidential guest support: Alter virtio default properties for protected guests David Gibson
2021-01-13 23:58 ` [PATCH v7 13/13] s390: Recognize confidential-guest-support option David Gibson
2021-01-14  9:10   ` Christian Borntraeger
2021-01-14  9:19     ` Christian Borntraeger
2021-01-14  9:24       ` Christian Borntraeger
2021-01-15  0:13         ` David Gibson
2021-01-14 11:45     ` David Gibson
2021-01-15 16:36   ` Cornelia Huck
2021-01-18 17:06     ` Christian Borntraeger

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