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From: Marc Zyngier <maz@kernel.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Sudeep Holla <sudeep.holla@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 10/18] arm64: KVM/debug: use EL1&0 stage 1 translation regime
Date: Wed, 15 Jan 2020 14:03:24 +0000
Message-ID: <5f141f153ceec55b4428d9c2d2dd9064@kernel.org> (raw)
In-Reply-To: <20200113163138.GP42593@e119886-lin.cambridge.arm.com>

On 2020-01-13 16:31, Andrew Murray wrote:
> On Sun, Dec 22, 2019 at 10:34:55AM +0000, Marc Zyngier wrote:
>> On Fri, 20 Dec 2019 14:30:17 +0000,
>> Andrew Murray <andrew.murray@arm.com> wrote:
>> >
>> > From: Sudeep Holla <sudeep.holla@arm.com>
>> >
>> > Now that we have all the save/restore mechanism in place, lets enable
>> > the translation regime used by buffer from EL2 stage 1 to EL1 stage 1
>> > on VHE systems.
>> >
>> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>> > [ Reword commit, don't trap to EL2 ]
>> 
>> Not trapping to EL2 for the case where we don't allow SPE in the
>> guest is not acceptable.
>> 
>> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
>> > ---
>> >  arch/arm64/kvm/hyp/switch.c | 2 ++
>> >  1 file changed, 2 insertions(+)
>> >
>> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
>> > index 67b7c160f65b..6c153b79829b 100644
>> > --- a/arch/arm64/kvm/hyp/switch.c
>> > +++ b/arch/arm64/kvm/hyp/switch.c
>> > @@ -100,6 +100,7 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
>> >
>> >  	write_sysreg(val, cpacr_el1);
>> >
>> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
>> >  	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
>> >  }
>> >  NOKPROBE_SYMBOL(activate_traps_vhe);
>> > @@ -117,6 +118,7 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
>> >  		__activate_traps_fpsimd32(vcpu);
>> >  	}
>> >
>> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
>> 
>> There is a _MASK macro that can replace this '3', and is in keeping
>> with the rest of the code.
>> 
>> It still remains that it looks like the wrong place to do this, and
>> vcpu_load seems much better. Why should you write to mdcr_el2 on each
>> entry to the guest, since you know whether it has SPE enabled at the
>> point where it gets scheduled?
> 
> For nVHE, the only reason we'd want to change E2PB on entry/exit of 
> guest
> would be if the host is also using SPE. If the host is using SPE whilst
> the vcpu is 'loaded' but we're not in the guest, then host SPE could 
> raise
> an interrupt - we need the E2PB bits to allow access from EL1 (host).

My comment was of course for VHE. nVHE hardly makes use of load/put at 
all,
for obvious reasons.

         M.
-- 
Jazz is not dead. It just smells funny...

  reply index

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-20 14:30 [PATCH v2 00/18] arm64: KVM: add SPE profiling support Andrew Murray
2019-12-20 14:30 ` [PATCH v2 01/18] dt-bindings: ARM SPE: highlight the need for PPI partitions on heterogeneous systems Andrew Murray
2019-12-20 14:30 ` [PATCH v2 02/18] arm64: KVM: reset E2PB correctly in MDCR_EL2 when exiting the guest(VHE) Andrew Murray
2019-12-21 13:12   ` Marc Zyngier
2019-12-24 10:29     ` Andrew Murray
2020-01-02 16:21       ` Andrew Murray
2019-12-20 14:30 ` [PATCH v2 03/18] arm64: KVM: define SPE data structure for each vcpu Andrew Murray
2019-12-21 13:19   ` Marc Zyngier
2019-12-24 12:01     ` Andrew Murray
2019-12-20 14:30 ` [PATCH v2 04/18] arm64: KVM: add SPE system registers to sys_reg_descs Andrew Murray
2019-12-20 14:30 ` [PATCH v2 05/18] arm64: KVM/VHE: enable the use PMSCR_EL12 on VHE systems Andrew Murray
2019-12-20 14:30 ` [PATCH v2 06/18] arm64: KVM: split debug save restore across vm/traps activation Andrew Murray
2019-12-20 14:30 ` [PATCH v2 07/18] arm64: KVM/debug: drop pmscr_el1 and use sys_regs[PMSCR_EL1] in kvm_cpu_context Andrew Murray
2019-12-20 14:30 ` [PATCH v2 08/18] arm64: KVM: add support to save/restore SPE profiling buffer controls Andrew Murray
2019-12-21 13:57   ` Marc Zyngier
2019-12-24 10:49     ` Andrew Murray
2019-12-24 15:17       ` Andrew Murray
2019-12-24 15:48         ` Marc Zyngier
2019-12-20 14:30 ` [PATCH v2 09/18] arm64: KVM: enable conditional save/restore full " Andrew Murray
2019-12-20 18:06   ` Mark Rutland
2019-12-24 12:15     ` Andrew Murray
2019-12-21 14:13   ` Marc Zyngier
2020-01-07 15:13     ` Andrew Murray
2020-01-08 11:17       ` Marc Zyngier
2020-01-08 11:58         ` Will Deacon
2020-01-08 12:36           ` Marc Zyngier
2020-01-08 13:10             ` Will Deacon
2020-01-09 11:23               ` Andrew Murray
2020-01-09 11:25                 ` Andrew Murray
2020-01-09 12:01                   ` Will Deacon
2020-01-10 10:54     ` Andrew Murray
2020-01-10 11:04       ` Andrew Murray
2020-01-10 11:51         ` Marc Zyngier
2020-01-10 12:12           ` Andrew Murray
2020-01-10 11:18       ` Marc Zyngier
2020-01-10 12:12         ` Andrew Murray
2020-01-10 13:34           ` Marc Zyngier
2019-12-20 14:30 ` [PATCH v2 10/18] arm64: KVM/debug: use EL1&0 stage 1 translation regime Andrew Murray
2019-12-22 10:34   ` Marc Zyngier
2019-12-24 11:11     ` Andrew Murray
2020-01-13 16:31     ` Andrew Murray
2020-01-15 14:03       ` Marc Zyngier [this message]
2019-12-20 14:30 ` [PATCH v2 11/18] KVM: arm64: don't trap Statistical Profiling controls to EL2 Andrew Murray
2019-12-20 18:08   ` Mark Rutland
2019-12-22 10:42   ` Marc Zyngier
2019-12-23 11:56     ` Andrew Murray
2019-12-23 12:05       ` Marc Zyngier
2019-12-23 12:10         ` Andrew Murray
2020-01-09 17:25           ` Andrew Murray
2020-01-09 17:42             ` Mark Rutland
2020-01-09 17:46               ` Andrew Murray
2019-12-20 14:30 ` [PATCH v2 12/18] KVM: arm64: add a new vcpu device control group for SPEv1 Andrew Murray
2019-12-22 11:03   ` Marc Zyngier
2019-12-24 12:30     ` Andrew Murray
2019-12-20 14:30 ` [PATCH v2 13/18] perf: arm_spe: Add KVM structure for obtaining IRQ info Andrew Murray
2019-12-22 11:24   ` Marc Zyngier
2019-12-24 12:35     ` Andrew Murray
2019-12-20 14:30 ` [PATCH v2 14/18] KVM: arm64: spe: Provide guest virtual interrupts for SPE Andrew Murray
2019-12-22 12:07   ` Marc Zyngier
2019-12-24 11:50     ` Andrew Murray
2019-12-24 12:42       ` Marc Zyngier
2019-12-24 13:08         ` Andrew Murray
2019-12-24 13:22           ` Marc Zyngier
2019-12-24 13:36             ` Andrew Murray
2019-12-24 13:46               ` Marc Zyngier
2019-12-20 14:30 ` [PATCH v2 15/18] perf: arm_spe: Handle guest/host exclusion flags Andrew Murray
2019-12-20 18:10   ` Mark Rutland
2019-12-22 12:10   ` Marc Zyngier
2019-12-23 12:10     ` Andrew Murray
2019-12-23 12:18       ` Marc Zyngier
2019-12-20 14:30 ` [PATCH v2 16/18] KVM: arm64: enable SPE support Andrew Murray
2019-12-20 14:30 ` [PATCH v2 17/18, KVMTOOL] update_headers: Sync kvm UAPI headers with linux v5.5-rc2 Andrew Murray
2019-12-20 14:30 ` [PATCH v2 18/18, KVMTOOL] kvm: add a vcpu feature for SPEv1 support Andrew Murray
2019-12-20 17:55 ` [PATCH v2 00/18] arm64: KVM: add SPE profiling support Mark Rutland
2019-12-24 12:54   ` Andrew Murray
2019-12-21 10:48 ` Marc Zyngier
2019-12-22 12:22   ` Marc Zyngier
2019-12-24 12:56     ` Andrew Murray

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