On Mon, Dec 10, 2018 at 01:36:40PM +0000, Will Deacon wrote: > On Fri, Dec 07, 2018 at 05:28:58PM +0000, Suzuki K Poulose wrote: > > > > > > On 07/12/2018 15:26, Will Deacon wrote: > > > On Fri, Dec 07, 2018 at 10:47:57AM +0000, Suzuki K Poulose wrote: > > > > On 12/06/2018 10:50 PM, Steve Capper wrote: > > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > > > > index f60081be9a1b..58fcc1edd852 100644 > > > > > --- a/arch/arm64/kernel/head.S > > > > > +++ b/arch/arm64/kernel/head.S > > > > > @@ -707,6 +707,7 @@ secondary_startup: > > > > > /* > > > > > * Common entry point for secondary CPUs. > > > > > */ > > > > > + bl __cpu_secondary_check52bitva > > > > > bl __cpu_setup // initialise processor > > > > > adrp x1, swapper_pg_dir > > > > > bl __enable_mmu > > > > > @@ -785,6 +786,31 @@ ENTRY(__enable_mmu) > > > > > ret > > > > > ENDPROC(__enable_mmu) > > > > > +ENTRY(__cpu_secondary_check52bitva) > > > > > +#ifdef CONFIG_ARM64_52BIT_VA > > > > > + ldr_l x0, vabits_user > > > > > + cmp x0, #52 > > > > > + b.ne 2f > + > > > > > + mrs_s x0, SYS_ID_AA64MMFR2_EL1 > > > > > + and x0, x0, #(0xf << ID_AA64MMFR2_LVA_SHIFT) > > > > > + cbnz x0, 2f > > > > > + > > > > > + adr_l x0, va52mismatch > > > > > + mov w1, #1 > > > > > + strb w1, [x0] > > > > > + dmb sy > > > > > + dc ivac, x0 // Invalidate potentially stale cache line > > > > > > > > You may have to clear this variable before a CPU is brought up to avoid > > > > raising a false error message when another secondary CPU doesn't boot > > > > for some other reason (say granule support) after a CPU failed with lack > > > > of 52bitva. It is really a crazy corner case. > > > > > > Can't we just follow the example set by the EL2 setup in the way that is > > > uses __boot_cpu_mode? In that case, we only need one variable and you can > > > detect a problem by comparing the two halves. > > > > The only difference here is, the support is bolted at boot CPU time and hence > > we need to verify each and every CPU, unlike the __boot_cpu_mode where we > > check for mismatch after the SMP CPUs are brought up. If we decide to make > > the choice later, something like that could work. The only caveat is the 52bit > > kernel VA will have to do something like the above. > > So looking at this a bit more, I think we're better off repurposing the > upper bits of the early boot status word to contain a reason code, rather > than introducing new variables for every possible mismatch. > > Does the untested diff below look remotely sane to you? > > Will > Thanks Will, This looks good to me, I will test now and fold this into a patch. Cheers, -- Steve
