Re: [PATCH] mei: improve Denverton HSM & IFSI support

[Lukas Bulwahn]

On Fri, Aug 20, 2021 at 5:45 PM Alex Williamson
<alex.williamson@xxxxxxxxxx> wrote:
>
> On Fri, 20 Aug 2021 10:28:21 +0200
> Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx> wrote:
>
> > On Thu, Aug 19, 2021 at 10:10 PM Alex Williamson
> > <alex.williamson@xxxxxxxxxx> wrote:
> > >
> > > On Thu, 19 Aug 2021 10:07:03 -0500
> > > Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> > >
> > > > [+cc Alex]
> > > >
> > > > On Thu, Aug 19, 2021 at 04:51:14PM +0200, Lukas Bulwahn wrote:
> > > > > The Intel Denverton chip provides HSM & IFSI. In order to access
> > > > > HSM & IFSI at the same time, provide two HECI hardware IDs for accessing.
> > > > >
> > > > > Suggested-by: Ionel-Catalin Mititelu <ionel-catalin.mititelu@xxxxxxxxx>
> > > > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
> > > > > ---
> > > > > Tomas, please pick this quick helpful extension for the hardware.
> > > > >
> > > > >  drivers/misc/mei/hw-me-regs.h | 3 ++-
> > > > >  drivers/misc/mei/pci-me.c     | 1 +
> > > > >  drivers/pci/quirks.c          | 3 +++
> > > > >  3 files changed, 6 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/misc/mei/hw-me-regs.h b/drivers/misc/mei/hw-me-regs.h
> > > > > index cb34925e10f1..c1c41912bb72 100644
> > > > > --- a/drivers/misc/mei/hw-me-regs.h
> > > > > +++ b/drivers/misc/mei/hw-me-regs.h
> > > > > @@ -68,7 +68,8 @@
> > > > >  #define MEI_DEV_ID_BXT_M      0x1A9A  /* Broxton M */
> > > > >  #define MEI_DEV_ID_APL_I      0x5A9A  /* Apollo Lake I */
> > > > >
> > > > > -#define MEI_DEV_ID_DNV_IE     0x19E5  /* Denverton IE */
> > > > > +#define MEI_DEV_ID_DNV_IE  0x19E5  /* Denverton for HECI1 - IFSI */
> > > > > +#define MEI_DEV_ID_DNV_IE_2        0x19E6  /* Denverton 2 for HECI2 - HSM */
> > > > >
> > > > >  #define MEI_DEV_ID_GLK        0x319A  /* Gemini Lake */
> > > > >
> > > > > diff --git a/drivers/misc/mei/pci-me.c b/drivers/misc/mei/pci-me.c
> > > > > index c3393b383e59..30827cd2a1c2 100644
> > > > > --- a/drivers/misc/mei/pci-me.c
> > > > > +++ b/drivers/misc/mei/pci-me.c
> > > > > @@ -77,6 +77,7 @@ static const struct pci_device_id mei_me_pci_tbl[] = {
> > > > >     {MEI_PCI_DEVICE(MEI_DEV_ID_APL_I, MEI_ME_PCH8_CFG)},
> > > > >
> > > > >     {MEI_PCI_DEVICE(MEI_DEV_ID_DNV_IE, MEI_ME_PCH8_CFG)},
> > > > > +   {MEI_PCI_DEVICE(MEI_DEV_ID_DNV_IE_2, MEI_ME_PCH8_SPS_CFG)},
> > > > >
> > > > >     {MEI_PCI_DEVICE(MEI_DEV_ID_GLK, MEI_ME_PCH8_CFG)},
> > > > >
> > > > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > > > > index 6899d6b198af..2ab767ef8469 100644
> > > > > --- a/drivers/pci/quirks.c
> > > > > +++ b/drivers/pci/quirks.c
> > > > > @@ -4842,6 +4842,9 @@ static const struct pci_dev_acs_enabled {
> > > > >     { PCI_VENDOR_ID_INTEL, 0x15b7, pci_quirk_mf_endpoint_acs },
> > > > >     { PCI_VENDOR_ID_INTEL, 0x15b8, pci_quirk_mf_endpoint_acs },
> > > > >     { PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_rciep_acs },
> > > > > +   /* Denverton */
> > > > > +   { PCI_VENDOR_ID_INTEL, 0x19e5, pci_quirk_mf_endpoint_acs },
> > > > > +   { PCI_VENDOR_ID_INTEL, 0x19e6, pci_quirk_mf_endpoint_acs },
> > > >
> > > > This looks like it should be a separate patch with a commit log that
> > > > explains it.  For example, see these:
> > > >
> > > >   db2f77e2bd99 ("PCI: Add ACS quirk for Broadcom BCM57414 NIC")
> > > >   3247bd10a450 ("PCI: Add ACS quirk for Intel Root Complex Integrated Endpoints")
> > > >   299bd044a6f3 ("PCI: Add ACS quirk for Zhaoxin Root/Downstream Ports")
> > > >   0325837c51cb ("PCI: Add ACS quirk for Zhaoxin multi-function devices")
> > > >   76e67e9e0f0f ("PCI: Add ACS quirk for Amazon Annapurna Labs root ports")
> > > >   46b2c32df7a4 ("PCI: Add ACS quirk for iProc PAXB")
> > > >   01926f6b321b ("PCI: Add ACS quirk for HXT SD4800")
> > > >
> > > > It should be acked by somebody at Intel since this quirk relies on
> > > > behavior of the device for VM security.
> > >
> > > +1 Thanks Bjorn.  I got curious and AFAICT these functions are the
> > > interface for the host system to communicate with "Innovation Engine"
> > > processors within the SoC, which seem to be available for system
> > > builders to innovate and differentiate system firmware features.  I'm
> > > not sure then how we can assume a specific interface ("HSM" or "IFSI",
> > > whatever those are) for each function, nor of course how we can assume
> > > isolation between them.  Thanks,
> >
> > Alex, I got a Denverton hardware with Innovation Engine and the
> > specific system firmware (basically delivered from Intel). To make use
> > of that hardware, someone at Intel suggested adding these PCI ACS
> > quirks. It is unclear to me if there are various different Denverton
> > systems out there (I only got one!) with many different system
> > firmware variants for the Innovation Engine or if there is just one
> > Denverton with IE support and with one firmware from Intel, i.e., the
> > one I got.
> >
> > If there is only one or two variants of the Denverton with Innovation
> > Engine firmware out there, then we could add this ACS quirk here
> > unconditionally (basically assuming that if the other firmware is
> > there, the IE would just do the right thing, e.g., deny any operation
> > for a non-existing firmware function), right? Just adding a commit
> > similar to the commits Bjorn pointed out above. Otherwise, we would
> > need to make that conditional for possible different variants, but I
> > would need a bit more guidance from you on which other variants exist
> > and how one can differentiate between them.
>
> Hi Lukas,
>
> I'm looking at the C3000 datasheet, Intel document #337018-002, where I
> see:
>
> 1.2.7 Innovation Engine (IE)
>         ...
>         For the IE, the system builder can install an embedded
>         operating system, drivers and application they develop on their
>         own, or purchase them from a third-party vendor. Intel does not
>         provide operating systems, drivers or applications for the IE.
>

Well, IMHO, my observation of what Intel provided to me clearly
contradicts that statement. It seems that Intel did provide an
operating system, driver and applications for the IE, and suggested
modifying/extending the kernel sources for that purpose beyond what
was already existing in the kernel tree, which already suggests by
itself that Intel has a specific driver and application for the IE in
mind.

> 15.2.3.1 Interrupt Timer Sub System (ITSS)
>         ...
>         The Innovation Engine (IE) has a sideband connection to the
>         ITSS components.
>
> 16 Power Management Controller (PMC)
>         ...
>         16.2 Feature List
>                 ...
>                 • Interacts with the SoC Innovation Engine (IE)
>
> Table 16-4. Causes of SMI and SCI
>         ...
>         [IE can cause SMI or SCI]
>
> 16.10.1 Initiating State Changes when in the G0 (S0) Working State
>         ...
>         The Intel® Management Engine and Innovation Engine firmware
>         each has a mechanism to turn off a hung system similar to the
>         Power-Button Override by writing bits in their power-management
>         control registers.
>
> And the apparent coup de grâce:
>
> 37 Innovation Engine
>         The Innovation Engine (IE) is an optional, complete, embedded
>         engine intended to enable SoC customers to provide their own
>         custom system management. This chapter provides a brief
>         overview of the IE. It is reserved for system-builder code, not
>         for Intel firmware since Intel supplies IE hardware only. IE
>         activation is not required for normal system operation.
>         ...
>         IE is a completely optional feature, and is disabled by default
>         in the silicon. It can be enabled by system builders and OEMs
>         to run signed firmware created by the system builder or a third
>         party software vendor. IE is not like the Intel® Management
>         Engine (Intel® ME) where Intel provides the HW plus a complete
>         FW solution. Intel only provides IE hardware (along with
>         collateral and tools enabling).
>
> For the HECI, I see:
>
> 37.3 Architectural Overview
>         ...
>         The devices exposed by the IE subsystem to the Host Root Space
>         are:
>                 • HECI (1, 2 and 3) – These functions define the
>                   mechanism for host software and IE firmware to
>                   communicate. This device exposes three PCI functions
>                   to the host during PCI bus enumeration. The message
>                   format is OEM dependent and communication between
>                   host and IE subsystem takes place via circular
>                   buffers and control/status registers. This function
>                   supports host MSI, SMI and SCI# interrupt generation
>                   mechanisms.
>
>
> So I don't see how the datasheet supports that there's either any
> specific API defined per HECI interface or that these functions would
> ever be intended in a generic way for independent use of by a userspace
> driver or VM.  Perhaps with DMI or ACPI info an HECI could be
> associated to a specific vendor API, by why we'd describe them as using
> isolated IOMMU grouping is a complete mystery to me.  Thanks,
>

I agree with that mystery, but I do not know if I should rather trust
the Intel documentation you cite or simply the bits and pieces that
already landed in the kernel tree here for the Denverton IE.

Am I right that we are basically stuck here without any further
explanation by somebody from Intel?

Do I also get it right that:

If we would trust the Intel documentation, we would not really see the
purpose of the existing line
MEI_PCI_DEVICE(MEI_DEV_ID_DNV_IE, MEI_ME_PCH8_CFG) in
drivers/misc/mei/pci-me.c, added with commit f7ee8ead151f ("mei: me:
add denverton innovation engine device IDs"), because that also
depends on the existence of a specific system-builder code?

Thanks for all your explanations and pointers, Alex.

Lukas