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From: Andrew Murray <andrew.murray@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: 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 11/18] KVM: arm64: don't trap Statistical Profiling controls to EL2
Date: Mon, 23 Dec 2019 12:10:42 +0000
Message-ID: <20191223121042.GC42593@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <1bb190091362262021dbaf41b5fe601e@www.loen.fr>

On Mon, Dec 23, 2019 at 12:05:12PM +0000, Marc Zyngier wrote:
> On 2019-12-23 11:56, Andrew Murray wrote:
> > On Sun, Dec 22, 2019 at 10:42:05AM +0000, Marc Zyngier wrote:
> > > On Fri, 20 Dec 2019 14:30:18 +0000,
> > > Andrew Murray <andrew.murray@arm.com> wrote:
> > > >
> > > > As we now save/restore the profiler state there is no need to trap
> > > > accesses to the statistical profiling controls. Let's unset the
> > > > _TPMS bit.
> > > >
> > > > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> > > > ---
> > > >  arch/arm64/kvm/debug.c | 2 --
> > > >  1 file changed, 2 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
> > > > index 43487f035385..07ca783e7d9e 100644
> > > > --- a/arch/arm64/kvm/debug.c
> > > > +++ b/arch/arm64/kvm/debug.c
> > > > @@ -88,7 +88,6 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu
> > > *vcpu)
> > > >   *  - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
> > > >   *  - Debug ROM Address (MDCR_EL2_TDRA)
> > > >   *  - OS related registers (MDCR_EL2_TDOSA)
> > > > - *  - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
> > > >   *
> > > >   * Additionally, KVM only traps guest accesses to the debug
> > > registers if
> > > >   * the guest is not actively using them (see the
> > > KVM_ARM64_DEBUG_DIRTY
> > > > @@ -111,7 +110,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu
> > > *vcpu)
> > > >  	 */
> > > >  	vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) &
> > > MDCR_EL2_HPMN_MASK;
> > > >  	vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
> > > > -				MDCR_EL2_TPMS |
> > > 
> > > No. This is an *optional* feature (the guest could not be presented
> > > with the SPE feature, or the the support simply not be compiled in).
> > > 
> > > If the guest is not allowed to see the feature, for whichever
> > > reason,
> > > the traps *must* be enabled and handled.
> > 
> > I'll update this (and similar) to trap such registers when we don't
> > support
> > SPE in the guest.
> > 
> > My original concern in the cover letter was in how to prevent the guest
> > from attempting to use these registers in the first place - I think the
> > solution I was looking for is to trap-and-emulate ID_AA64DFR0_EL1 such
> > that
> > the PMSVer bits indicate that SPE is not emulated.
> 
> That, and active trapping of the SPE system registers resulting in injection
> of an UNDEF into the offending guest.

Yes that's no problem.

Thanks,

Andrew Murray

> 
> 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
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 [this message]
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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