From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36143) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTzNS-0002G4-4u for qemu-devel@nongnu.org; Thu, 11 Feb 2016 17:06:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aTzNR-0006vD-7K for qemu-devel@nongnu.org; Thu, 11 Feb 2016 17:06:18 -0500 From: "Gabriel L. Somlo" Date: Thu, 11 Feb 2016 17:06:05 -0500 Message-Id: <1455228365-13666-6-git-send-email-somlo@cmu.edu> In-Reply-To: <1455228365-13666-1-git-send-email-somlo@cmu.edu> References: <1455228365-13666-1-git-send-email-somlo@cmu.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH v8 5/5] fw_cfg: document ACPI device node information List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, ehabkost@redhat.com, mst@redhat.com, matt@codeblueprint.co.uk, stefanha@gmail.com, ard.biesheuvel@linaro.org, leif.lindholm@linaro.org, luto@amacapital.net, qemu-arm@nongnu.org, kraxel@redhat.com, pbonzini@redhat.com, imammedo@redhat.com, lersek@redhat.com, rth@twiddle.net Signed-off-by: Gabriel Somlo Reviewed-by: Laszlo Ersek Reviewed-by: Marc Mar=C3=AD --- docs/specs/fw_cfg.txt | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt index 2099ad9..5414140 100644 --- a/docs/specs/fw_cfg.txt +++ b/docs/specs/fw_cfg.txt @@ -84,6 +84,15 @@ Selector Register address: Base + 8 (2 bytes) Data Register address: Base + 0 (8 bytes) DMA Address address: Base + 16 (8 bytes) =20 +=3D=3D ACPI Interface =3D=3D + +The fw_cfg device is defined with ACPI ID "QEMU0002". Since we expect +ACPI tables to be passed into the guest through the fw_cfg device itself= , +the guest-side firmware can not use ACPI to find fw_cfg. However, once t= he +firmware is finished setting up ACPI tables and hands control over to th= e +guest kernel, the latter can use the fw_cfg ACPI node for a more accurat= e +inventory of in-use IOport or MMIO regions. + =3D=3D Firmware Configuration Items =3D=3D =20 =3D=3D=3D Signature (Key 0x0000, FW_CFG_SIGNATURE) =3D=3D=3D --=20 2.4.3