Messages in this thread | | | Date | Wed, 21 Jan 2015 20:37:00 +0800 | From | Hanjun Guo <> | Subject | Re: [PATCH v6 17/17] Documentation: ACPI for ARM64 |
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Hi Christoffer,
Sorry for the late reply, I got no answer yet but with one question below.
On 2015年01月20日 04:33, Christoffer Dall wrote: > Hi, > > On Sun, Jan 04, 2015 at 06:55:18PM +0800, Hanjun Guo wrote: >> From: Graeme Gregory <graeme.gregory@linaro.org> >> >> Add documentation for the guidelines of how to use ACPI >> on ARM64. >> >> Reviewed-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com> >> Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org> >> Signed-off-by: Al Stone <al.stone@linaro.org> >> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org> >> --- >> Documentation/arm64/arm-acpi.txt | 327 +++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 327 insertions(+) >> create mode 100644 Documentation/arm64/arm-acpi.txt >> >> diff --git a/Documentation/arm64/arm-acpi.txt b/Documentation/arm64/arm-acpi.txt >> new file mode 100644 >> index 0000000..21e7020 >> --- /dev/null >> +++ b/Documentation/arm64/arm-acpi.txt >> @@ -0,0 +1,327 @@ >> +ACPI on ARMv8 Servers >> +--------------------- >> +ACPI can be used for ARMv8 general purpose servers designed to follow >> +the ARM SBSA (Server Base System Architecture) and SBBR (Server Base >> +Boot Requirements) specifications, currently available to those with >> +an ARM login at http://silver.arm.com. >> + >> +The ARMv8 kernel implements the reduced hardware model of ACPI version >> +5.1 and later. Links to the specification and all external documents >> +it refers to are managed by the UEFI Forum. The specification is >> +available at http://www.uefi.org/specifications and external documents >> +can be found via http://www.uefi.org/acpi. >> + >> +If an ARMv8 system does not meet the requirements of the SBSA, or cannot >> +be described using the mechanisms defined in the required ACPI specifications, >> +then it is likely that Device Tree (DT) is more suitable than ACPI for the >> +hardware. >> + >> + >> +Relationship with Device Tree >> +----------------------------- >> +ACPI support in drivers and subsystems for ARMv8 should never be mutually >> +exclusive with DT support at compile time. >> + >> +At boot time the kernel will only use one description method depending on >> +parameters passed from the bootloader (including kernel bootargs). >> + >> +Regardless of whether DT or ACPI is used, the kernel must always be capable >> +of booting with either scheme (in kernels with both schemes enabled at compile >> +time). >> + >> + >> +Booting using ACPI tables >> +------------------------- >> +The only defined method for passing ACPI tables to the kernel on ARMv8 >> +is via the UEFI system configuration table. >> + > > This is a bit concerning for the approach we are currently taking to > support ACPI on Xen [1]. > > Background: Xen is a tiny hypervisor which cannot parse the DSDT or any > other non-static table. Xen relies on Linux in Dom0 to manage most > (basically everything except the GIC, serial port, SMMU, and timers) > hardware resources and relies on Dom0 to parse the ACPI tables. > > While Xen itself is typically booted by UEFI and finds RSDP through the > UEFI system table, Xen does NOT run another UEFI instance to boot Dom0 > nor does it pass through the presence of UEFI to Dom0 in any way. > Instead, it just created a DT (with modifications concerning the > hardware mentioned above) and boots Linux in Dom0 directly (on x86 any > required UEFI call is performed through paravirtualized hypercalls). > > In the case of ACPI, Xen adds a property to the chosen node and > populates it with the RDSP in Dom0's address space. Patches have not
Sorry I'm not familiar with hypervisor, I have question here about x86 on xen, how ACPI works on XEN for x86?
Thanks Hanjun
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