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authorLaszlo Ersek <lersek@redhat.com>2017-02-01 15:33:57 +0100
committerLaszlo Ersek <lersek@redhat.com>2017-03-09 15:03:27 +0100
commit198a46d768fb90d2f9b16e26451b4814e7469eaf (patch)
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MdeModulePkg/AcpiTableDxe: improve FADT.{DSDT,X_DSDT} mutual exclusion
The ACPI specification, up to and including revision 5.1 Errata A, allows the DSDT and X_DSDT fields to be both set in the FADT. (Obviously, this only makes sense if the DSDT address is representable in 4 bytes.) Starting with 5.1 Errata B, specifically for Mantis 1393 <https://mantis.uefi.org/mantis/view.php?id=1393>, the spec requires at most one of DSDT and X_DSDT to be set to a nonzero value. MdeModulePkg/AcpiTableDxe handles this mutual exclusion somewhat inconsistently. - If the caller of EFI_ACPI_TABLE_PROTOCOL.InstallAcpiTable() installs the tables in "DSDT, FADT" order, then we enforce the exclusion between the DSDT and X_DSDT fields: DSDT under 4GB FADT.DSDT FADT.X_DSDT [VARIANT B] -------------- --------- ----------- yes set clear no clear set This behavior conforms to 5.1 Errata B. (And it's not required by earlier versions of the spec.) - If the caller passes in the tables in "FADT, DSDT" relative order, then we do not enforce the exclusion: DSDT under 4GB FADT.DSDT FADT.X_DSDT [VARIANT A] -------------- --------- ----------- yes set set no clear set This satisfies 5.1 Errata A and earlier, but breaks 5.1 Errata B and later. Unify the handling of both relative orders. In particular, check the major and minor version numbers in the FADT. If the FADT version is strictly before 5.1, then implement [VARIANT A]. If the FADT version is equal to or larger than 5.1, then implement [VARIANT B]. We make three observations: - We can't check the FADT table version precisely against "5.1 Errata B"; erratum levels are not captured in the table. We err in the safe direction, namely we enforce the exclusion for "5.1" and "5.1 Errata A". - The same applies to "6.0" versus "6.0 Errata A". Because we cannot distinguish these two, we consider "6.0" to be "equal to or larger than 5.1", and apply [VARIANT B], enforcing the exclusion. - While a blanket [VARIANT B] would be simpler, there is a significant benefit to [VARIANT A], under the spec versions that permit it: compatibility with a wider range of OSPMs (typically, older ones). For example, Igor reported about a "DELL R430 system with rev4 FADT where DSDT and X_DSDT are pointing to the same address". Michael also reported about several systems that exhibit the same. Regression tested with the following KVM guests (QEMU built at ata0def594286d, "Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging", 2017-01-30): - OVMF: boot and S3 suspend/resume - Ia32, Q35, SMM - Fedlet 20141209 - Ia32X64, Q35, SMM - Fedora 22 - Windows 7 - Windows 8.1 - Windows 10 - Windows Server 2008 R2 - Windows Server 2012 R2 - Windows Server 2016 Tech Preview 4 - X64, I440FX, no SMM - Fedora 24 - RHEL-6.7 - RHEL-7.2-ish - ArmVirtQemu: boot test with virtio-gpu - AARCH64 - Fedora 24 - RHELSA-7.3 - openSUSE Tumbleweed (4.8.4-based) This change is connected to ASWG ticket <https://mantis.uefi.org/mantis/view.php?id=1757>, which is now closed/fixed. Cc: Al Stone <ahs3@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Feng Tian <feng.tian@intel.com> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Jiewen Yao <jiewen.yao@intel.com> Cc: Leo Duran <leo.duran@amd.com> Cc: Michael Tsirkin <mtsirkin@redhat.com> Cc: Phil Dennis-Jordan <phil@philjordan.eu> Cc: Star Zeng <star.zeng@intel.com> Reported-by: Phil Dennis-Jordan <phil@philjordan.eu> Suggested-by: Igor Mammedov <imammedo@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu> Reviewed-by: Jiewen Yao <jiewen.yao@intel.com> Reviewed-by: Star Zeng <star.zeng@intel.com>
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