From: Paolo Bonzini <pbonzini@redhat.com>
To: Tobin Feldman-Fitzthum <tobin@linux.ibm.com>
Cc: Steve Rutherford <srutherford@google.com>,
Ashish Kalra <Ashish.Kalra@amd.com>,
Thomas Lendacky <thomas.lendacky@amd.com>,
Brijesh Singh <brijesh.singh@amd.com>,
"Habkost, Eduardo" <ehabkost@redhat.com>,
kvm <kvm@vger.kernel.org>, "S. Tsirkin, Michael" <mst@redhat.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
"James E . J . Bottomley" <jejb@linux.ibm.com>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel <qemu-devel@nongnu.org>,
David Gilbert <dgilbert@redhat.com>,
Hubertus Franke <frankeh@us.ibm.com>,
Dov Murik <dovmurik@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 00/13] Add support for Mirror VM.
Date: Wed, 18 Aug 2021 01:20:31 +0200 [thread overview]
Message-ID: <CABgObfYz8=+u1nsiSiLbOo7t7uSyQzro+crRsK4fANS1_TZR9Q@mail.gmail.com> (raw)
In-Reply-To: <37796fd1-bbc2-f22c-b786-eb44f4d473b9@linux.ibm.com>
On Tue, Aug 17, 2021 at 10:51 PM Tobin Feldman-Fitzthum
<tobin@linux.ibm.com> wrote:
> This is essentially what we do in our prototype, although we have an
> even simpler approach. We have a 1:1 mapping that maps an address to
> itself with the cbit set. During Migration QEMU asks the migration
> handler to import/export encrypted pages and provides the GPA for said
> page. Since the migration handler only exports/imports encrypted pages,
> we can have the cbit set for every page in our mapping. We can still use
> OVMF functions with these mappings because they are on encrypted pages.
> The MH does need to use a few shared pages (to communicate with QEMU,
> for instance), so we have another mapping without the cbit that is at a
> large offset.
>
> I think this is basically equivalent to what you suggest. As you point
> out above, this approach does require that any page that will be
> exported/imported by the MH is mapped in the guest. Is this a bad
> assumption?
It should work well enough in the common case; and with SNP it looks
like it is a necessary assumption anyway. *shrug*
It would be a bit ugly because QEMU has to constantly convert
ram_addr_t's to guest physical addresses and back. But that's not a
performance problem.
The only important bit is that the encryption status bitmap be indexed
by ram_addr_t. This lets QEMU detect the problem of a ram_addr_t that
is marked encrypted but is not currently mapped, and abort migration.
> The Migration Handler in OVMF is not a contiguous region of memory. The
> MH uses OVMF helper functions that are allocated in various regions of
> runtime memory. I guess I can see how separating the memory of the MH
> and the guest OS could be positive. On the other hand, since the MH is
> in OVMF, it is fundamentally designed to coexist with the guest OS.
IIRC runtime services are not SMP-safe, so the migration helper cannot
coexist with the guest OS without extra care. I checked quickly and
CryptoPkg/Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c does not
use any lock, so it would be bad if both OS-invoked runtime services
and the MH invoked the CryptoPkg malloc at the same time.
Paolo
next prev parent reply other threads:[~2021-08-17 23:20 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 13:25 [RFC PATCH 00/13] Add support for Mirror VM Ashish Kalra
2021-08-16 13:26 ` [RFC PATCH 01/13] machine: Add mirrorvcpus=N suboption to -smp Ashish Kalra
2021-08-16 21:23 ` Eric Blake
2021-08-16 13:27 ` [RFC PATCH 02/13] hw/boards: Add mirror_vcpu flag to CPUArchId Ashish Kalra
2021-08-16 13:27 ` [RFC PATCH 03/13] hw/i386: Mark mirror vcpus in possible_cpus Ashish Kalra
2021-08-16 13:27 ` [RFC PATCH 04/13] hw/acpi: Don't include mirror vcpus in ACPI tables Ashish Kalra
2021-08-16 13:28 ` [RFC PATCH 05/13] cpu: Add boolean mirror_vcpu field to CPUState Ashish Kalra
2021-08-16 13:28 ` [RFC PATCH 06/13] hw/i386: Set CPUState.mirror_vcpu=true for mirror vcpus Ashish Kalra
2021-08-16 13:29 ` [RFC PATCH 07/13] kvm: Add Mirror VM ioctl and enable cap interfaces Ashish Kalra
2021-08-16 13:29 ` [RFC PATCH 08/13] kvm: Add Mirror VM support Ashish Kalra
2021-08-16 13:29 ` [RFC PATCH 09/13] kvm: create Mirror VM and share primary VM's encryption context Ashish Kalra
2021-08-16 13:30 ` [RFC PATCH 10/13] softmmu/cpu: Skip mirror vcpu's for pause, resume and synchronization Ashish Kalra
2021-08-16 13:30 ` [RFC PATCH 11/13] kvm/apic: Disable in-kernel APIC support for mirror vcpu's Ashish Kalra
2021-08-16 13:31 ` [RFC PATCH 12/13] hw/acpi: disable modern CPU hotplug interface " Ashish Kalra
2021-08-16 13:31 ` [RFC PATCH 13/13] hw/i386/pc: reduce fw_cfg boot cpu count taking into account " Ashish Kalra
2021-08-16 14:01 ` [RFC PATCH 00/13] Add support for Mirror VM Claudio Fontana
2021-08-16 14:15 ` Paolo Bonzini
2021-08-16 14:23 ` Daniel P. Berrangé
2021-08-16 15:00 ` Paolo Bonzini
2021-08-16 15:16 ` Daniel P. Berrangé
2021-08-16 15:35 ` Paolo Bonzini
2021-08-16 14:44 ` Ashish Kalra
2021-08-16 14:58 ` Paolo Bonzini
2021-08-16 15:13 ` Ashish Kalra
2021-08-16 15:38 ` Paolo Bonzini
2021-08-16 15:48 ` Dr. David Alan Gilbert
2021-08-18 10:31 ` Ashish Kalra
2021-08-18 11:25 ` James Bottomley
2021-08-18 15:31 ` Dr. David Alan Gilbert
2021-08-18 15:35 ` James Bottomley
2021-08-18 15:43 ` Dr. David Alan Gilbert
2021-08-18 16:28 ` James Bottomley
2021-08-18 17:30 ` Dr. David Alan Gilbert
2021-08-18 18:51 ` James Bottomley
2021-08-16 17:23 ` Dr. David Alan Gilbert
2021-08-16 23:53 ` Steve Rutherford
2021-08-17 7:05 ` Michael S. Tsirkin
2021-08-17 8:38 ` Dr. David Alan Gilbert
2021-08-17 14:08 ` Ashish Kalra
2021-08-17 16:32 ` Paolo Bonzini
2021-08-17 20:50 ` Tobin Feldman-Fitzthum
2021-08-17 22:04 ` Steve Rutherford
2021-08-18 15:32 ` Tobin Feldman-Fitzthum
2021-08-18 19:04 ` Dr. David Alan Gilbert
2021-08-18 21:42 ` Tobin Feldman-Fitzthum
2021-08-19 8:22 ` Dr. David Alan Gilbert
2021-08-19 14:06 ` James Bottomley
2021-08-19 14:28 ` Dr. David Alan Gilbert
2021-08-19 22:10 ` James Bottomley
2021-08-23 12:26 ` Dr. David Alan Gilbert
2021-08-23 16:28 ` Tobin Feldman-Fitzthum
2021-08-19 14:07 ` Tobin Feldman-Fitzthum
2021-08-17 23:20 ` Paolo Bonzini [this message]
2021-08-17 21:54 ` Steve Rutherford
2021-08-17 22:37 ` Paolo Bonzini
2021-08-17 22:57 ` James Bottomley
2021-08-17 23:10 ` Steve Rutherford
2021-08-18 2:49 ` James Bottomley
2021-08-18 14:06 ` Ashish Kalra
2021-08-18 17:07 ` Ashish Kalra
2021-08-16 15:07 Tobin Feldman-Fitzthum
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