From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: kvm@vger.kernel.org, Marc Zyngier <marc.zyngier@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 23/23] arm64: Panic when VHE and non VHE CPUs coexist
Date: Tue, 9 Feb 2016 12:02:17 +0000 [thread overview]
Message-ID: <20160209120217.GE16122@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <20160208162402.GC14146@leverpostej>
On Mon, Feb 08, 2016 at 04:24:03PM +0000, Mark Rutland wrote:
> On Mon, Feb 08, 2016 at 04:04:46PM +0000, Catalin Marinas wrote:
> > On Wed, Feb 03, 2016 at 06:00:16PM +0000, Marc Zyngier wrote:
> > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> > > index 6f2f377..f9b6a5b 100644
> > > --- a/arch/arm64/kernel/head.S
> > > +++ b/arch/arm64/kernel/head.S
> > > @@ -578,7 +578,24 @@ ENTRY(set_cpu_boot_mode_flag)
> > > 1: str w20, [x1] // This CPU has booted in EL1
> > > dmb sy
> > > dc ivac, x1 // Invalidate potentially stale cache line
> > > + adr_l x1, __run_cpu_mode
> > > + ldr w0, [x1]
> > > + mrs x20, CurrentEL
> > > + cbz x0, skip_el_check
> > > + cmp x0, x20
> > > + bne mismatched_el
> > > ret
> > > +skip_el_check: // Only the first CPU gets to set the rule
> > > + str w20, [x1]
> > > + dmb sy
> > > + dc ivac, x1 // Invalidate potentially stale cache line
> > > + ret
> > > +mismatched_el:
> > > + str w20, [x1, #4]
> > > + dmb sy
> > > + dc ivac, x1 // Invalidate potentially stale cache line
> > > +1: wfi
> > > + b 1b
> > > ENDPROC(set_cpu_boot_mode_flag)
> >
> > Do we need to wait for the D-cache maintenance completion before
> > entering WFI (like issuing a DSB)? Same for the skip_el_check path
> > before the RET.
>
> We would need that to complete the maintenance, yes.
>
> However, given we're going into WFI immediately afterwards, and not
> signalling completion to other CPUs, what we gain is somewhat
> questionable.
>
> Perhaps it's always better to do the maintenance on the read side (for
> consistency with [1]).
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-February/404661.html
While [1] looks clearer to me, it seems that it is not consistent with
the rest of the head.S file. Maybe we can clean them up as a separate
patch and leave the dc ivac here. We also seem to miss barriers in other
similar situations in head.S.
--
Catalin
next prev parent reply other threads:[~2016-02-09 12:02 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 17:59 [PATCH v3 00/23] arm64: Virtualization Host Extension support Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 01/23] arm/arm64: KVM: Add hook for C-based stage2 init Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 02/23] arm64: KVM: Switch to " Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 03/23] arm/arm64: Add new is_kernel_in_hyp_mode predicate Marc Zyngier
2016-02-08 14:41 ` Catalin Marinas
2016-02-03 17:59 ` [PATCH v3 04/23] arm64: Allow the arch timer to use the HYP timer Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 05/23] arm64: Add ARM64_HAS_VIRT_HOST_EXTN feature Marc Zyngier
2016-02-08 14:42 ` Catalin Marinas
2016-02-03 17:59 ` [PATCH v3 06/23] arm64: KVM: Skip HYP setup when already running in HYP Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 07/23] arm64: KVM: VHE: Patch out use of HVC Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 08/23] arm64: KVM: VHE: Patch out kern_hyp_va Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 09/23] arm64: KVM: VHE: Introduce unified system register accessors Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 10/23] arm64: KVM: VHE: Differenciate host/guest sysreg save/restore Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 11/23] arm64: KVM: VHE: Split save/restore of registers shared between guest and host Marc Zyngier
2016-02-04 19:15 ` Christoffer Dall
2016-02-03 18:00 ` [PATCH v3 12/23] arm64: KVM: VHE: Use unified system register accessors Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 13/23] arm64: KVM: VHE: Enable minimal sysreg save/restore Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 14/23] arm64: KVM: VHE: Make __fpsimd_enabled VHE aware Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 15/23] arm64: KVM: VHE: Implement VHE activate/deactivate_traps Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 16/23] arm64: KVM: VHE: Use unified sysreg accessors for timer Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 17/23] arm64: KVM: VHE: Add fpsimd enabling on guest access Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 18/23] arm64: KVM: VHE: Add alternative panic handling Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 19/23] arm64: KVM: Move most of the fault decoding to C Marc Zyngier
2016-02-04 19:20 ` Christoffer Dall
2016-02-08 14:44 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 20/23] arm64: perf: Count EL2 events if the kernel is running in HYP Marc Zyngier
2016-02-04 19:23 ` Christoffer Dall
2016-02-05 9:02 ` Marc Zyngier
2016-02-08 14:48 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 21/23] arm64: hw_breakpoint: Allow EL2 breakpoints if " Marc Zyngier
2016-02-08 15:56 ` Catalin Marinas
2016-02-08 16:45 ` Marc Zyngier
2016-02-08 16:52 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 22/23] arm64: VHE: Add support for running Linux in EL2 mode Marc Zyngier
2016-02-04 19:25 ` Christoffer Dall
2016-02-08 15:58 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 23/23] arm64: Panic when VHE and non VHE CPUs coexist Marc Zyngier
2016-02-04 19:25 ` Christoffer Dall
2016-02-08 16:04 ` Catalin Marinas
2016-02-08 16:24 ` Mark Rutland
2016-02-09 12:02 ` Catalin Marinas [this message]
2016-02-04 19:26 ` [PATCH v3 00/23] arm64: Virtualization Host Extension support Christoffer Dall
2016-02-05 8:56 ` Marc Zyngier
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