Re: [PATCH v3] arm64: Unify WORKAROUND_SPECULATIVE_AT_{NVHE,VHE}

From: Will Deacon <will@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
	Steven Price <steven.price@arm.com>,
	James Morse <james.morse@arm.com>,
	Andrew Scull <ascull@google.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3] arm64: Unify WORKAROUND_SPECULATIVE_AT_{NVHE,VHE}
Date: Mon, 4 May 2020 12:26:24 +0100	[thread overview]
Message-ID: <20200504112624.GA1326@willie-the-truck> (raw)
In-Reply-To: <7b3cc0b0a3fa6d08d8c8413e4498d485@kernel.org>

On Mon, May 04, 2020 at 12:13:02PM +0100, Marc Zyngier wrote:
> On 2020-05-04 11:55, Will Deacon wrote:
> > On Mon, May 04, 2020 at 10:48:58AM +0100, Andrew Scull wrote:
> > > Errata 1165522, 1319367 and 1530923 each allow TLB entries to be
> > > allocated as a result of a speculative AT instruction. In order to
> > > avoid mandating VHE on certain affected CPUs, apply the workaround to
> > > both the nVHE and the VHE case for all affected CPUs.
> > > 
> > > Signed-off-by: Andrew Scull <ascull@google.com>
> > > CC: Marc Zyngier <maz@kernel.org>
> > > CC: James Morse <james.morse@arm.com>
> > > CC: Suzuki K Poulose <suzuki.poulose@arm.com>
> > > CC: Will Deacon <will@kernel.org>
> > > CC: Steven Price <steven.price@arm.com>
> > > ---
> > > From v2 <20200422161346.67325-1-ascull@google.com>:
> > >  - const_cap -> final_cap merge correction
> > >  - based on 5.7 rc4
> > > ---
> > >  arch/arm64/Kconfig                | 39
> > > ++++++++++++++-----------------
> > >  arch/arm64/include/asm/cpucaps.h  | 15 ++++++------
> > >  arch/arm64/include/asm/kvm_host.h |  4 ----
> > >  arch/arm64/include/asm/kvm_hyp.h  |  2 +-
> > >  arch/arm64/kernel/cpu_errata.c    | 25 +++++++++-----------
> > >  arch/arm64/kvm/hyp/switch.c       |  6 ++---
> > >  arch/arm64/kvm/hyp/sysreg-sr.c    |  6 +++--
> > >  arch/arm64/kvm/hyp/tlb.c          | 11 +++++----
> > >  8 files changed, 50 insertions(+), 58 deletions(-)
> > 
> > Acked-by: Will Deacon <will@kernel.org>
> > 
> > We'll probably run into some trivial conflicts with the arm64 tree, but
> > I'm happy to put this on a branch if it helps. Marc?
> 
> I'd rather we avoid the conflicts by not repainting all the capabilities
> and just leave a capability unused until the next one fills in the slot.

I think we'll run into conflicts whatever we do, so I'd say the patch is
alright like it is.

> But otherwise, I'll take a stable branch.

Ok, let me cook that today.

> Also the current state of the KVM/arm tree is a bit crap as none of the
> fixes have made it into Linus' tree yet, and I don't have a good base
> for the current queue (the welcome-home branch could create havoc).

Seriously? I'll reply on your pull to see if I can help.

Will

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