All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jarkko Sakkinen <jarkko@kernel.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Francisco Blas Izquierdo Riera <klondike@klondike.es>,
	linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v2] PCI: Add DMA alias for Intel Corporation 8 Series HECI
Date: Wed, 7 Dec 2022 14:05:03 +0000	[thread overview]
Message-ID: <Y5Cdj2wS+FLjjx2Q@kernel.org> (raw)
In-Reply-To: <20221129182756.GA727866@bhelgaas>

On Tue, Nov 29, 2022 at 12:27:56PM -0600, Bjorn Helgaas wrote:
> Does the TPM work under Windows?  If so, it would suggest that there's
> a different way to use it that doesn't require the quirk or the DMAR
> override.  Or maybe it only works on Windows without the IOMMU being
> enabled?

Haswell was the first generation having firmware TPM, and had fTPM
implementation that was flakky in many ways (e.g. Intel TXT still required
a discrete TPM so servers never used it). We have some workarounds for it
already in place.

I'm almost 100% confident nobody seriously tried to use it on server
side and/or together with MMIO.

> Naive question: apparently the TPM is doing DMA reads/writes.  I see
> tpm_crb.c doing MMIO mappings (ioremap()), but I don't see any DMA
> mappings.  Is that implicit or done elsewhere?

Firmware does this. Kernel does not and should not care how it does
it because it is not part of the specification [1]. Kernel cares only
of getting a buffer pointed out by the firmware.

[1] Section 6.5.3 in https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/

BR, Jarkko

      reply	other threads:[~2022-12-07 14:06 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-21 16:40 [PATCH v2] PCI: Add DMA alias for Intel Corporation 8 Series HECI Francisco Blas Izquierdo Riera
2022-11-21 17:54 ` Bjorn Helgaas
2022-11-21 19:39   ` Robin Murphy
2022-11-21 23:20     ` klondike
2022-11-21 23:14   ` klondike
2022-11-29 18:27 ` Bjorn Helgaas
2022-12-07 14:05   ` Jarkko Sakkinen [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Y5Cdj2wS+FLjjx2Q@kernel.org \
    --to=jarkko@kernel.org \
    --cc=bhelgaas@google.com \
    --cc=helgaas@kernel.org \
    --cc=klondike@klondike.es \
    --cc=linux-pci@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
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.