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From: Marc Zyngier <maz@kernel.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: will@kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
	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 02/18] arm64: KVM: reset E2PB correctly in MDCR_EL2 when exiting the guest(VHE)
Date: Sat, 21 Dec 2019 13:12:14 +0000
Message-ID: <20191221131214.769a140e@why> (raw)
In-Reply-To: <20191220143025.33853-3-andrew.murray@arm.com>

On Fri, 20 Dec 2019 14:30:09 +0000
Andrew Murray <andrew.murray@arm.com> wrote:

> From: Sudeep Holla <sudeep.holla@arm.com>
> 
> On VHE systems, the reset value for MDCR_EL2.E2PB=b00 which defaults
> to profiling buffer using the EL2 stage 1 translations. 

Does the reset value actually matter here? I don't see it being
specific to VHE systems, and all we're trying to achieve is to restore
the SPE configuration to a state where it can be used by the host.

> However if the
> guest are allowed to use profiling buffers changing E2PB settings, we

How can the guest be allowed to change E2PB settings? Or do you mean
here that allowing the guest to use SPE will mandate changes of the
E2PB settings, and that we'd better restore the hypervisor state once
we exit?

> need to ensure we resume back MDCR_EL2.E2PB=b00. Currently we just
> do bitwise '&' with MDCR_EL2_E2PB_MASK which will retain the value.
> 
> So fix it by clearing all the bits in E2PB.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>  arch/arm64/kvm/hyp/switch.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 72fbbd86eb5e..250f13910882 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -228,9 +228,7 @@ void deactivate_traps_vhe_put(void)
>  {
>  	u64 mdcr_el2 = read_sysreg(mdcr_el2);
>  
> -	mdcr_el2 &= MDCR_EL2_HPMN_MASK |
> -		    MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT |
> -		    MDCR_EL2_TPMS;
> +	mdcr_el2 &= MDCR_EL2_HPMN_MASK | MDCR_EL2_TPMS;
>  
>  	write_sysreg(mdcr_el2, mdcr_el2);
>  

I'm OK with this change, but I believe the commit message could use
some tidying up.

Thanks,

	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 [this message]
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
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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