From: Anthony Martin <ality@pbrane.org>
To: 9front@9front.org
Subject: Re: 9FRONT "EMAILSCHADEN" RELEASED
Date: Mon, 19 Oct 2020 15:38:59 -0700 [thread overview]
Message-ID: <20201019223859.GC243000@alice> (raw)
In-Reply-To: <0230698894072CDFA179F53B8EE1DA03@ewsd.inri.net>
sl@stanleylieber.com once said:
> pc, pc64: remove mystery "type" bits in pcicfgrw*raw() (fixes qemu, thanks mischief)
In changeset 78891f472fbf, cinap wrote:
the access functions for pci config space in config mode #1
used to set bit 0 in the register offset if the access was
to a device on any bus different from 0.
it is completely unclear why this was done and i can't find
any documentation on this.
but for sure, this breaks all pci config spacess access to
pci devices behind a bridge on qemu. with -trace pci* it
was discovered that all config space register offsets on
devies behind pci brige where off by one.
Our code looks like it was a slight misreading of the specification
and the change looks good. However, the original behavior should have
been innocuous for any conforming host bridge:
For Type 1 translations, the host bridge directly copies the
contents of the CONFIG_ADDRESS register (excluding bits 31 and
0) onto the PCI AD lines during the address phase of a
configuration transaction making sure that AD[1::0] is "01".
(from PCI Local Bus Specification, Revision 3.0, §3.2.2.3.2)
Note the phrase "excluding bits 31 and 0". Also, the PCI-PCI bridge
in QEMU should be doing a Type 1 to Type 0 translation before the
device behind the bridge sees the address.
Cheers,
Anthony
next parent reply other threads:[~2020-10-19 22:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <0230698894072CDFA179F53B8EE1DA03@ewsd.inri.net>
2020-10-19 22:38 ` Anthony Martin [this message]
2020-10-24 22:29 ` [9front] " cinap_lenrek
2020-10-24 23:28 ` cinap_lenrek
2020-10-24 23:57 ` Thaddeus Woskowiak
2020-10-25 0:49 ` Alex Musolino
2020-11-02 0:54 ` kokamoto
2020-11-02 5:22 ` Eli Cohen
2020-11-04 13:24 ` cinap_lenrek
2020-11-04 13:29 ` cinap_lenrek
2020-11-05 3:27 ` kokamoto
2020-10-19 4:03 sl
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