linux-kernel - Re: [PATCH v4 10/18] KVM: arm64: nv: Describe trap behaviour of MDCR

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Message-ID: <Zxz9YonLVsaLuMEJ@linux.dev>
Date: Sat, 26 Oct 2024 14:32:02 +0000
From: Oliver Upton <oliver.upton@...ux.dev>
To: kvmarm@...ts.linux.dev
Cc: Marc Zyngier <maz@...nel.org>, Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/18] KVM: arm64: nv: Describe trap behaviour of
 MDCR_EL2.HPMN

On Fri, Oct 25, 2024 at 06:23:45PM +0000, Oliver Upton wrote:
> MDCR_EL2.HPMN splits the PMU event counters into two ranges: the first
> range is accessible from all ELs, and the second range is accessible
> only to EL2/3. Supposing the guest hypervisor allows direct access to
> the PMU counters from the L2, KVM needs to locally handle those
> accesses.
> 
> Add a new complex trap configuration for HPMN that checks if the counter
> index is accessible to the current context. As written, the architecture
> suggests HPMN only causes PMEVCNTR<n>_EL0 to trap, though intuition (and
> the pseudocode) suggest that the trap applies to PMEVTYPER<n>_EL0 as
> well.
> 
> Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
> ---
>  arch/arm64/kvm/emulate-nested.c | 160 +++++++++++++++++++-------------
>  arch/arm64/kvm/pmu-emul.c       |  18 ++++
>  include/kvm/arm_pmu.h           |   6 ++
>  3 files changed, 120 insertions(+), 64 deletions(-)

Gonna squash in the following to fix !CONFIG_HW_PERF_EVENTS builds.

diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index e6103df9ef5d..feb5d1d35f0f 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -188,7 +188,7 @@ static inline u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
-static inline bool kvm_pmu_counter_is_hyp(struct kvm_vcpu *vcpu)
+static inline bool kvm_pmu_counter_is_hyp(struct kvm_vcpu *vcpu, unsigned int idx)
 {
 	return false;
 }

-- 
Thanks,
Oliver