* [PATCH] [RESEND] docs: Add spec of OVMF GUIDed table for SEV guests
@ 2021-12-20 11:11 Dov Murik
0 siblings, 0 replies; 5+ messages in thread
From: Dov Murik @ 2021-12-20 11:11 UTC (permalink / raw)
To: Dov Murik, qemu-devel
Add docs/specs/sev-guest-firmware.rst which describes the GUIDed table
in the end of OVMF's image which is parsed by QEMU, and currently used
to describe some values for SEV and SEV-ES guests.
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
docs/specs/index.rst | 1 +
docs/specs/sev-guest-firmware.rst | 125 ++++++++++++++++++++++++++++++
2 files changed, 126 insertions(+)
create mode 100644 docs/specs/sev-guest-firmware.rst
diff --git a/docs/specs/index.rst b/docs/specs/index.rst
index ecc43896bb..2a35700fb3 100644
--- a/docs/specs/index.rst
+++ b/docs/specs/index.rst
@@ -18,3 +18,4 @@ guest hardware that is specific to QEMU.
acpi_mem_hotplug
acpi_pci_hotplug
acpi_nvdimm
+ sev-guest-firmware
diff --git a/docs/specs/sev-guest-firmware.rst b/docs/specs/sev-guest-firmware.rst
new file mode 100644
index 0000000000..3f7f082df5
--- /dev/null
+++ b/docs/specs/sev-guest-firmware.rst
@@ -0,0 +1,125 @@
+====================================================
+QEMU/Guest Firmware Interface for AMD SEV and SEV-ES
+====================================================
+
+Overview
+========
+
+The guest firmware image (OVMF) may contain some configuration entries
+which are used by QEMU before the guest launches. These are listed in a
+GUIDed table at a known location in the firmware image. QEMU parses
+this table when it loads the firmware image into memory, and then QEMU
+reads individual entries when their values are needed.
+
+Though nothing in the table structure is SEV-specific, currently all the
+entries in the table are related to SEV and SEV-ES features.
+
+
+Table parsing in QEMU
+---------------------
+
+The table is parsed from the footer: first the presence of the table
+footer GUID (96b582de-1fb2-45f7-baea-a366c55a082d) at 0xffffffd0 is
+verified. If that is found, two bytes at 0xffffffce are the entire
+table length.
+
+Then the table is scanned backwards looking for the specific entry GUID.
+
+QEMU files related to parsing and scanning the OVMF table:
+ - ``hw/i386/pc_sysfw_ovmf.c``
+
+The edk2 firmware code that constructs this structure is in the
+`OVMF Reset Vector file`_.
+
+
+Table memory layout
+-------------------
+
++------------+--------+-----------------------------------------+
+| GPA | Length | Description |
++============+========+=========================================+
+| 0xffffff80 | 4 | Zero padding |
++------------+--------+-----------------------------------------+
+| 0xffffff84 | 4 | SEV hashes table base address |
++------------+--------+-----------------------------------------+
+| 0xffffff88 | 4 | SEV hashes table size (=0x400) |
++------------+--------+-----------------------------------------+
+| 0xffffff8c | 2 | SEV hashes table entry length (=0x1a) |
++------------+--------+-----------------------------------------+
+| 0xffffff8e | 16 | SEV hashes table GUID: |
+| | | 7255371f-3a3b-4b04-927b-1da6efa8d454 |
++------------+--------+-----------------------------------------+
+| 0xffffff9e | 4 | SEV secret block base address |
++------------+--------+-----------------------------------------+
+| 0xffffffa2 | 4 | SEV secret block size (=0xc00) |
++------------+--------+-----------------------------------------+
+| 0xffffffa6 | 2 | SEV secret block entry length (=0x1a) |
++------------+--------+-----------------------------------------+
+| 0xffffffa8 | 16 | SEV secret block GUID: |
+| | | 4c2eb361-7d9b-4cc3-8081-127c90d3d294 |
++------------+--------+-----------------------------------------+
+| 0xffffffb8 | 4 | SEV-ES AP reset RIP |
++------------+--------+-----------------------------------------+
+| 0xffffffbc | 2 | SEV-ES reset block entry length (=0x16) |
++------------+--------+-----------------------------------------+
+| 0xffffffbe | 16 | SEV-ES reset block entry GUID: |
+| | | 00f771de-1a7e-4fcb-890e-68c77e2fb44e |
++------------+--------+-----------------------------------------+
+| 0xffffffce | 2 | Length of entire table including table |
+| | | footer GUID and length (=0x72) |
++------------+--------+-----------------------------------------+
+| 0xffffffd0 | 16 | OVMF GUIDed table footer GUID: |
+| | | 96b582de-1fb2-45f7-baea-a366c55a082d |
++------------+--------+-----------------------------------------+
+| 0xffffffe0 | 8 | Application processor entry point code |
++------------+--------+-----------------------------------------+
+| 0xffffffe8 | 8 | "\0\0\0\0VTF\0" |
++------------+--------+-----------------------------------------+
+| 0xfffffff0 | 16 | Reset vector code |
++------------+--------+-----------------------------------------+
+
+
+Table entries description
+=========================
+
+SEV-ES reset block
+------------------
+
+Entry GUID: 00f771de-1a7e-4fcb-890e-68c77e2fb44e
+
+For the initial boot of an AP under SEV-ES, the "reset" RIP must be
+programmed to the RAM area defined by this entry. The entry's format
+is:
+
+* IP value [0:15]
+* CS segment base [31:16]
+
+A hypervisor reads the CS segment base and IP value. The CS segment
+base value represents the high order 16-bits of the CS segment base, so
+the hypervisor must left shift the value of the CS segment base by 16
+bits to form the full CS segment base for the CS segment register. It
+would then program the EIP register with the IP value as read.
+
+
+SEV secret block
+----------------
+
+Entry GUID: 4c2eb361-7d9b-4cc3-8081-127c90d3d294
+
+This describes the guest RAM area where the hypervisor should inject the
+Guest Owner secret (using SEV_LAUNCH_SECRET).
+
+
+SEV hashes table
+----------------
+
+Entry GUID: 7255371f-3a3b-4b04-927b-1da6efa8d454
+
+This describes the guest RAM area where the hypervisor should install a
+table describing the hashes of certain firmware configuration device
+files that would otherwise be passed in unchecked. The current use is
+for the kernel, initrd and command line values, but others may be added.
+
+
+.. _OVMF Reset Vector file:
+ https://github.com/tianocore/edk2/blob/master/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
--
2.25.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] [RESEND] docs: Add spec of OVMF GUIDed table for SEV guests
2022-02-15 6:21 ` Dov Murik
@ 2022-03-07 0:13 ` Philippe Mathieu-Daudé
0 siblings, 0 replies; 5+ messages in thread
From: Philippe Mathieu-Daudé @ 2022-03-07 0:13 UTC (permalink / raw)
To: Dov Murik, Philippe Mathieu-Daudé
Cc: Tom Lendacky, Ashish Kalra, Brijesh Singh, James Bottomley,
qemu-devel, Dr. David Alan Gilbert, Tobin Feldman-Fitzthum,
Daniel P. Berrangé,
Paolo Bonzini, Gerd Hoffmann
On 15/2/22 07:21, Dov Murik wrote:
> On 04/01/2022 20:07, Daniel P. Berrangé wrote:
>> On Mon, Jan 03, 2022 at 11:14:13AM +0200, Dov Murik wrote:
>>> Add docs/specs/sev-guest-firmware.rst which describes the GUIDed table
>>> in the end of OVMF's image which is parsed by QEMU, and currently used
>>> to describe some values for SEV and SEV-ES guests.
>>>
>>> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
>>> ---
>>> docs/specs/index.rst | 1 +
>>> docs/specs/sev-guest-firmware.rst | 125 ++++++++++++++++++++++++++++++
>>> 2 files changed, 126 insertions(+)
>>> create mode 100644 docs/specs/sev-guest-firmware.rst
>>
>> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>>
>
> Phil,
>
> Can you please add this to your queue? (I assume this is yours
> because this is documentation of OVMF-QEMU interface)
Catching up for 7.0 I see Gerd merged it as 0a2a40da4f. Thank you Gerd!
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] [RESEND] docs: Add spec of OVMF GUIDed table for SEV guests
2022-01-04 18:07 ` Daniel P. Berrangé
@ 2022-02-15 6:21 ` Dov Murik
2022-03-07 0:13 ` Philippe Mathieu-Daudé
0 siblings, 1 reply; 5+ messages in thread
From: Dov Murik @ 2022-02-15 6:21 UTC (permalink / raw)
To: Philippe Mathieu-Daudé
Cc: Tom Lendacky, Ashish Kalra, Brijesh Singh, James Bottomley,
qemu-devel, Dr. David Alan Gilbert, Dov Murik,
Tobin Feldman-Fitzthum, Daniel P. Berrangé,
Paolo Bonzini, Gerd Hoffmann
On 04/01/2022 20:07, Daniel P. Berrangé wrote:
> On Mon, Jan 03, 2022 at 11:14:13AM +0200, Dov Murik wrote:
>> Add docs/specs/sev-guest-firmware.rst which describes the GUIDed table
>> in the end of OVMF's image which is parsed by QEMU, and currently used
>> to describe some values for SEV and SEV-ES guests.
>>
>> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
>> ---
>> docs/specs/index.rst | 1 +
>> docs/specs/sev-guest-firmware.rst | 125 ++++++++++++++++++++++++++++++
>> 2 files changed, 126 insertions(+)
>> create mode 100644 docs/specs/sev-guest-firmware.rst
>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>
Phil,
Can you please add this to your queue? (I assume this is yours
because this is documentation of OVMF-QEMU interface)
The patch itself:
https://lore.kernel.org/qemu-devel/20220103091413.2869-1-dovmurik@linux.ibm.com/
(I see I didn't CC you then. Sorry.)
Thanks,
Dov
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] [RESEND] docs: Add spec of OVMF GUIDed table for SEV guests
2022-01-03 9:14 Dov Murik
@ 2022-01-04 18:07 ` Daniel P. Berrangé
2022-02-15 6:21 ` Dov Murik
0 siblings, 1 reply; 5+ messages in thread
From: Daniel P. Berrangé @ 2022-01-04 18:07 UTC (permalink / raw)
To: Dov Murik
Cc: Tom Lendacky, Ashish Kalra, Brijesh Singh, James Bottomley,
qemu-devel, Dr. David Alan Gilbert, Tobin Feldman-Fitzthum,
Paolo Bonzini
On Mon, Jan 03, 2022 at 11:14:13AM +0200, Dov Murik wrote:
> Add docs/specs/sev-guest-firmware.rst which describes the GUIDed table
> in the end of OVMF's image which is parsed by QEMU, and currently used
> to describe some values for SEV and SEV-ES guests.
>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---
> docs/specs/index.rst | 1 +
> docs/specs/sev-guest-firmware.rst | 125 ++++++++++++++++++++++++++++++
> 2 files changed, 126 insertions(+)
> create mode 100644 docs/specs/sev-guest-firmware.rst
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] [RESEND] docs: Add spec of OVMF GUIDed table for SEV guests
@ 2022-01-03 9:14 Dov Murik
2022-01-04 18:07 ` Daniel P. Berrangé
0 siblings, 1 reply; 5+ messages in thread
From: Dov Murik @ 2022-01-03 9:14 UTC (permalink / raw)
To: qemu-devel
Cc: Tom Lendacky, Ashish Kalra, Daniel P. Berrangé,
James Bottomley, Dr. David Alan Gilbert, Dov Murik,
Tobin Feldman-Fitzthum, Brijesh Singh, Paolo Bonzini
Add docs/specs/sev-guest-firmware.rst which describes the GUIDed table
in the end of OVMF's image which is parsed by QEMU, and currently used
to describe some values for SEV and SEV-ES guests.
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
docs/specs/index.rst | 1 +
docs/specs/sev-guest-firmware.rst | 125 ++++++++++++++++++++++++++++++
2 files changed, 126 insertions(+)
create mode 100644 docs/specs/sev-guest-firmware.rst
diff --git a/docs/specs/index.rst b/docs/specs/index.rst
index ecc43896bb..2a35700fb3 100644
--- a/docs/specs/index.rst
+++ b/docs/specs/index.rst
@@ -18,3 +18,4 @@ guest hardware that is specific to QEMU.
acpi_mem_hotplug
acpi_pci_hotplug
acpi_nvdimm
+ sev-guest-firmware
diff --git a/docs/specs/sev-guest-firmware.rst b/docs/specs/sev-guest-firmware.rst
new file mode 100644
index 0000000000..3f7f082df5
--- /dev/null
+++ b/docs/specs/sev-guest-firmware.rst
@@ -0,0 +1,125 @@
+====================================================
+QEMU/Guest Firmware Interface for AMD SEV and SEV-ES
+====================================================
+
+Overview
+========
+
+The guest firmware image (OVMF) may contain some configuration entries
+which are used by QEMU before the guest launches. These are listed in a
+GUIDed table at a known location in the firmware image. QEMU parses
+this table when it loads the firmware image into memory, and then QEMU
+reads individual entries when their values are needed.
+
+Though nothing in the table structure is SEV-specific, currently all the
+entries in the table are related to SEV and SEV-ES features.
+
+
+Table parsing in QEMU
+---------------------
+
+The table is parsed from the footer: first the presence of the table
+footer GUID (96b582de-1fb2-45f7-baea-a366c55a082d) at 0xffffffd0 is
+verified. If that is found, two bytes at 0xffffffce are the entire
+table length.
+
+Then the table is scanned backwards looking for the specific entry GUID.
+
+QEMU files related to parsing and scanning the OVMF table:
+ - ``hw/i386/pc_sysfw_ovmf.c``
+
+The edk2 firmware code that constructs this structure is in the
+`OVMF Reset Vector file`_.
+
+
+Table memory layout
+-------------------
+
++------------+--------+-----------------------------------------+
+| GPA | Length | Description |
++============+========+=========================================+
+| 0xffffff80 | 4 | Zero padding |
++------------+--------+-----------------------------------------+
+| 0xffffff84 | 4 | SEV hashes table base address |
++------------+--------+-----------------------------------------+
+| 0xffffff88 | 4 | SEV hashes table size (=0x400) |
++------------+--------+-----------------------------------------+
+| 0xffffff8c | 2 | SEV hashes table entry length (=0x1a) |
++------------+--------+-----------------------------------------+
+| 0xffffff8e | 16 | SEV hashes table GUID: |
+| | | 7255371f-3a3b-4b04-927b-1da6efa8d454 |
++------------+--------+-----------------------------------------+
+| 0xffffff9e | 4 | SEV secret block base address |
++------------+--------+-----------------------------------------+
+| 0xffffffa2 | 4 | SEV secret block size (=0xc00) |
++------------+--------+-----------------------------------------+
+| 0xffffffa6 | 2 | SEV secret block entry length (=0x1a) |
++------------+--------+-----------------------------------------+
+| 0xffffffa8 | 16 | SEV secret block GUID: |
+| | | 4c2eb361-7d9b-4cc3-8081-127c90d3d294 |
++------------+--------+-----------------------------------------+
+| 0xffffffb8 | 4 | SEV-ES AP reset RIP |
++------------+--------+-----------------------------------------+
+| 0xffffffbc | 2 | SEV-ES reset block entry length (=0x16) |
++------------+--------+-----------------------------------------+
+| 0xffffffbe | 16 | SEV-ES reset block entry GUID: |
+| | | 00f771de-1a7e-4fcb-890e-68c77e2fb44e |
++------------+--------+-----------------------------------------+
+| 0xffffffce | 2 | Length of entire table including table |
+| | | footer GUID and length (=0x72) |
++------------+--------+-----------------------------------------+
+| 0xffffffd0 | 16 | OVMF GUIDed table footer GUID: |
+| | | 96b582de-1fb2-45f7-baea-a366c55a082d |
++------------+--------+-----------------------------------------+
+| 0xffffffe0 | 8 | Application processor entry point code |
++------------+--------+-----------------------------------------+
+| 0xffffffe8 | 8 | "\0\0\0\0VTF\0" |
++------------+--------+-----------------------------------------+
+| 0xfffffff0 | 16 | Reset vector code |
++------------+--------+-----------------------------------------+
+
+
+Table entries description
+=========================
+
+SEV-ES reset block
+------------------
+
+Entry GUID: 00f771de-1a7e-4fcb-890e-68c77e2fb44e
+
+For the initial boot of an AP under SEV-ES, the "reset" RIP must be
+programmed to the RAM area defined by this entry. The entry's format
+is:
+
+* IP value [0:15]
+* CS segment base [31:16]
+
+A hypervisor reads the CS segment base and IP value. The CS segment
+base value represents the high order 16-bits of the CS segment base, so
+the hypervisor must left shift the value of the CS segment base by 16
+bits to form the full CS segment base for the CS segment register. It
+would then program the EIP register with the IP value as read.
+
+
+SEV secret block
+----------------
+
+Entry GUID: 4c2eb361-7d9b-4cc3-8081-127c90d3d294
+
+This describes the guest RAM area where the hypervisor should inject the
+Guest Owner secret (using SEV_LAUNCH_SECRET).
+
+
+SEV hashes table
+----------------
+
+Entry GUID: 7255371f-3a3b-4b04-927b-1da6efa8d454
+
+This describes the guest RAM area where the hypervisor should install a
+table describing the hashes of certain firmware configuration device
+files that would otherwise be passed in unchecked. The current use is
+for the kernel, initrd and command line values, but others may be added.
+
+
+.. _OVMF Reset Vector file:
+ https://github.com/tianocore/edk2/blob/master/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
--
2.25.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-03-07 0:15 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-12-20 11:11 [PATCH] [RESEND] docs: Add spec of OVMF GUIDed table for SEV guests Dov Murik
2022-01-03 9:14 Dov Murik
2022-01-04 18:07 ` Daniel P. Berrangé
2022-02-15 6:21 ` Dov Murik
2022-03-07 0:13 ` Philippe Mathieu-Daudé
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.