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Date: Mon, 15 Apr 2024 15:23:35 +0200
From: Andrew Jones <ajones@ventanamicro.com>
To: Atish Patra <atishp@rivosinc.com>
Cc: linux-kernel@vger.kernel.org, Anup Patel <anup@brainfault.org>, 
	Ajay Kaher <ajay.kaher@broadcom.com>, Albert Ou <aou@eecs.berkeley.edu>, 
	Alexandre Ghiti <alexghiti@rivosinc.com>, Alexey Makhalov <alexey.amakhalov@broadcom.com>, 
	Atish Patra <atishp@atishpatra.org>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>, Conor Dooley <conor.dooley@microchip.com>, 
	Juergen Gross <jgross@suse.com>, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, 
	linux-kselftest@vger.kernel.org, linux-riscv@lists.infradead.org, 
	Mark Rutland <mark.rutland@arm.com>, Palmer Dabbelt <palmer@dabbelt.com>, 
	Paolo Bonzini <pbonzini@redhat.com>, Paul Walmsley <paul.walmsley@sifive.com>, 
	Shuah Khan <shuah@kernel.org>, virtualization@lists.linux.dev, Will Deacon <will@kernel.org>, 
	x86@kernel.org
Subject: Re: [PATCH v6 14/24] RISC-V: KVM: Add perf sampling support for
 guests
Message-ID: <20240415-cdc6d5bc6c5145f9d6f54afc@orel>
References: <20240411000752.955910-1-atishp@rivosinc.com>
 <20240411000752.955910-15-atishp@rivosinc.com>
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On Wed, Apr 10, 2024 at 05:07:42PM -0700, Atish Patra wrote:
> KVM enables perf for guest via counter virtualization. However, the
> sampling can not be supported as there is no mechanism to enabled
> trap/emulate scountovf in ISA yet. Rely on the SBI PMU snapshot
> to provide the counter overflow data via the shared memory.
> 
> In case of sampling event, the host first sets the guest's LCOFI
> interrupt and injects to the guest via irq filtering mechanism defined
> in AIA specification. Thus, ssaia must be enabled in the host in order
> to use perf sampling in the guest. No other AIA dependency w.r.t kernel
> is required.
> 
> Reviewed-by: Anup Patel <anup@brainfault.org>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
>  arch/riscv/include/asm/csr.h          |  3 +-
>  arch/riscv/include/asm/kvm_vcpu_pmu.h |  3 ++
>  arch/riscv/include/uapi/asm/kvm.h     |  1 +
>  arch/riscv/kvm/aia.c                  |  5 ++
>  arch/riscv/kvm/vcpu.c                 | 15 ++++--
>  arch/riscv/kvm/vcpu_onereg.c          |  6 +++
>  arch/riscv/kvm/vcpu_pmu.c             | 68 +++++++++++++++++++++++++--
>  7 files changed, 93 insertions(+), 8 deletions(-)
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>