| Message ID | 1464142211-343-1-git-send-email-Wei.Chen@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
Hello Peng, On 25/05/16 13:37, Peng Fan wrote: > On Wed, May 25, 2016 at 10:10:11AM +0800, Wei Chen wrote: >> In ARM64, the MPIDR multiprocessing extensions bit is reserved to 1. >> So, the value check for this bit is no longer necessary on ARM64. > > From ARM DDI0487A.G, I found the U bit for MPIDR_EL1: > " > Indicates a Uniprocessor system, as distinct from PE 0 in a multiprocessor system. The possible > values of this bit are: > 0 Processor is part of a multiprocessor system. > 1 Processor is part of a uniprocessor system. > " > > It's not reserved to 1. Which doc are you refering to? Please read carefully the patch. The check on MPDIR_EL1.U is kept, only the check to the RES1 bit ('M' for Aarch32) is removed. Regards,
Hi Wei, On 25/05/16 03:10, Wei Chen wrote: > In ARM64, the MPIDR multiprocessing extensions bit is reserved to 1. Well, technically the bit is unamed for ARM64. So I would make clear that the name is from AArch32. Something along: "The bit 31 (former bit Multiprocessing extensions bit in AArch32) is always RES1 for AArch64." > So, the value check for this bit is no longer necessary on ARM64. > > Signed-off-by: Wei Chen <Wei.Chen@linaro.org> > --- > xen/arch/arm/arm64/head.S | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S > index 3090beb..91e2817 100644 > --- a/xen/arch/arm/arm64/head.S > +++ b/xen/arch/arm/arm64/head.S > @@ -267,7 +267,6 @@ common_start: > * find that multiprocessor extensions are > * present and the system is SMP */ > mrs x0, mpidr_el1 > - tbz x0, _MPIDR_SMP, 1f /* Multiprocessor extension not supported? */ > tbnz x0, _MPIDR_UP, 1f /* Uniprocessor system? */ > > ldr x13, =(~MPIDR_HWID_MASK) > Regards,
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S index 3090beb..91e2817 100644 --- a/xen/arch/arm/arm64/head.S +++ b/xen/arch/arm/arm64/head.S @@ -267,7 +267,6 @@ common_start: * find that multiprocessor extensions are * present and the system is SMP */ mrs x0, mpidr_el1 - tbz x0, _MPIDR_SMP, 1f /* Multiprocessor extension not supported? */ tbnz x0, _MPIDR_UP, 1f /* Uniprocessor system? */ ldr x13, =(~MPIDR_HWID_MASK)
In ARM64, the MPIDR multiprocessing extensions bit is reserved to 1. So, the value check for this bit is no longer necessary on ARM64. Signed-off-by: Wei Chen <Wei.Chen@linaro.org> --- xen/arch/arm/arm64/head.S | 1 - 1 file changed, 1 deletion(-)