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From: Mark Rutland <mark.rutland@arm.com>
To: Christoffer Dall <cdall@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, arnd@arndb.de,
	catalin.marinas@arm.com, kvmarm@lists.cs.columbia.edu,
	linux-arch@vger.kernel.org, marc.zyngier@arm.com,
	suzuki.poulose@arm.com, will.deacon@arm.com, yao.qi@arm.com,
	kernel-hardening@lists.openwall.com,
	linux-kernel@vger.kernel.org, awallis@codeaurora.org
Subject: Re: [PATCHv2 09/12] arm64/kvm: preserve host HCR_EL2 value
Date: Mon, 9 Apr 2018 15:57:09 +0100	[thread overview]
Message-ID: <20180409145709.dneotb6xaznw44c4@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20180206123915.GA21802@cbox>

On Tue, Feb 06, 2018 at 01:39:15PM +0100, Christoffer Dall wrote:
> On Mon, Nov 27, 2017 at 04:38:03PM +0000, Mark Rutland wrote:
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > index 525c01f48867..2205f0be3ced 100644
> > --- a/arch/arm64/kvm/hyp/switch.c
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -71,6 +71,8 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
> >  {
> >  	u64 val;
> >  
> > +	vcpu->arch.host_hcr_el2 = read_sysreg(hcr_el2);
> > +
> 
> Looking back at this, it seems excessive to switch this at every
> round-trip.  I think it should be possible to have this as a single
> global (or per-CPU) variable that gets restored directly when returning
> from the VM.

I suspect this needs to be per-cpu, to account for heterogeneous
systems.

I guess if we move hcr_el2 into kvm_cpu_context, that gives us a
per-vcpu copy for guests, and a per-cpu copy for the host (in the global
kvm_host_cpu_state).

I'll have a look at how gnarly that turns out. I'm not sure how we can
initialise that sanely for the !VHE case to match whatever el2_setup
did.

Thanks,
Mark.

  reply	other threads:[~2018-04-09 14:57 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-27 16:37 [PATCHv2 00/12] ARMv8.3 pointer authentication userspace support Mark Rutland
2017-11-27 16:37 ` [PATCHv2 01/12] asm-generic: mm_hooks: allow hooks to be overridden individually Mark Rutland
2017-11-27 16:37 ` [PATCHv2 02/12] arm64: add pointer authentication register bits Mark Rutland
2017-11-27 16:37 ` [PATCHv2 03/12] arm64/cpufeature: add ARMv8.3 id_aa64isar1 bits Mark Rutland
2017-11-27 16:37 ` [PATCHv2 04/12] arm64/cpufeature: detect pointer authentication Mark Rutland
2017-11-27 16:37 ` [PATCHv2 05/12] arm64: Don't trap host pointer auth use to EL2 Mark Rutland
2018-02-06 12:39   ` Christoffer Dall
2018-02-12 16:00     ` Mark Rutland
2017-11-27 16:38 ` [PATCHv2 06/12] arm64: add basic pointer authentication support Mark Rutland
2018-05-22 19:06   ` Adam Wallis
2017-11-27 16:38 ` [PATCHv2 07/12] arm64: expose user PAC bit positions via ptrace Mark Rutland
2017-11-27 16:38 ` [PATCHv2 08/12] arm64: perf: strip PAC when unwinding userspace Mark Rutland
2017-11-27 16:38 ` [PATCHv2 09/12] arm64/kvm: preserve host HCR_EL2 value Mark Rutland
2018-02-06 12:39   ` Christoffer Dall
2018-04-09 14:57     ` Mark Rutland [this message]
2018-04-09 19:03       ` Christoffer Dall
2017-11-27 16:38 ` [PATCHv2 10/12] arm64/kvm: context-switch ptrauth registers Mark Rutland
2018-02-06 12:38   ` Christoffer Dall
2018-03-09 14:28     ` Mark Rutland
2018-04-09 12:58       ` Christoffer Dall
2018-04-09 14:37         ` Mark Rutland
2017-11-27 16:38 ` [PATCHv2 11/12] arm64: enable pointer authentication Mark Rutland
2017-11-27 16:38 ` [PATCHv2 12/12] arm64: docs: document " Mark Rutland
2017-11-28 15:07   ` Andrew Jones
2017-12-04 12:39     ` Mark Rutland
2017-12-04 12:49       ` Andrew Jones

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