From: Leo Yan <leo.yan@arm.com>
To: Rob Herring <robh@kernel.org>
Cc: Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Jonathan Corbet <corbet@lwn.net>, Marc Zyngier <maz@kernel.org>,
Oliver Upton <oliver.upton@linux.dev>,
Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
James Clark <james.clark@linaro.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, kvmarm@lists.linux.dev
Subject: Re: [PATCH v19 09/11] arm64: Handle BRBE booting requirements
Date: Thu, 13 Feb 2025 12:27:19 +0000 [thread overview]
Message-ID: <20250213122719.GE235556@e132581.arm.com> (raw)
In-Reply-To: <CAL_JsqK7eBmRKL0AC99hj5AipL4jki5rrhSvbZCbUxa0vnEKMg@mail.gmail.com>
On Wed, Feb 12, 2025 at 03:21:46PM -0600, Rob Herring wrote:
[...]
> > > + - If the kernel is entered at EL1 and EL2 is present:
> > > +
> > > + - BRBCR_EL2.CC (bit 3) must be initialised to 0b1.
> > > + - BRBCR_EL2.MPRED (bit 4) must be initialised to 0b1.
> >
> > Should clarify BRBCR_EL2.TS to be initialised to 0b00 ? Arm ARM
> > claims the reset behaviour of the TS field is unknown value. The
> > assembly code below actually has initializes the TS field as zero.
>
> Humm, we don't currently care what it is initialized to because the
> timestamp is never used. We would care in the future if we use
> timestamps. Will 0b00 be the only correct value? I'm not sure.
In initializaton phase, if set BRBCR_EL2.TS = 0b00, then the timestamp
will be decided by BRBCR_EL1.TS. I expect the BRBE driver will always
write BRBCR_EL1.TS.
Thanks,
Leo
next prev parent reply other threads:[~2025-02-13 12:27 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-03 0:42 [PATCH v19 00/11] arm64/perf: Enable branch stack sampling Rob Herring (Arm)
2025-02-03 0:42 ` [PATCH v19 01/11] perf: arm_pmuv3: Call kvm_vcpu_pmu_resync_el0() before enabling counters Rob Herring (Arm)
2025-02-03 4:07 ` Anshuman Khandual
2025-02-03 0:42 ` [PATCH v19 02/11] perf: arm_pmu: Don't disable counter in armpmu_add() Rob Herring (Arm)
2025-02-03 6:04 ` Anshuman Khandual
2025-02-03 0:42 ` [PATCH v19 03/11] perf: arm_pmuv3: Don't disable counter in armv8pmu_enable_event() Rob Herring (Arm)
2025-02-03 6:38 ` Anshuman Khandual
2025-02-03 0:42 ` [PATCH v19 04/11] perf: arm_v7_pmu: Drop obvious comments for enabling/disabling counters and interrupts Rob Herring (Arm)
2025-02-03 4:09 ` Anshuman Khandual
2025-02-03 0:42 ` [PATCH v19 05/11] perf: arm_v7_pmu: Don't disable counter in (armv7|krait_|scorpion_)pmu_enable_event() Rob Herring (Arm)
2025-02-03 6:54 ` Anshuman Khandual
2025-02-03 0:43 ` [PATCH v19 06/11] perf: apple_m1: Don't disable counter in m1_pmu_enable_event() Rob Herring (Arm)
2025-02-03 8:10 ` Anshuman Khandual
2025-02-03 0:43 ` [PATCH v19 07/11] perf: arm_pmu: Move PMUv3-specific data Rob Herring (Arm)
2025-02-03 8:16 ` Anshuman Khandual
2025-02-03 0:43 ` [PATCH v19 08/11] arm64/sysreg: Add BRBE registers and fields Rob Herring (Arm)
2025-02-03 8:32 ` Anshuman Khandual
2025-02-03 0:43 ` [PATCH v19 09/11] arm64: Handle BRBE booting requirements Rob Herring (Arm)
2025-02-03 8:47 ` Anshuman Khandual
2025-02-12 12:10 ` Leo Yan
2025-02-12 21:21 ` Rob Herring
2025-02-13 12:27 ` Leo Yan [this message]
2025-02-03 0:43 ` [PATCH v19 10/11] KVM: arm64: nvhe: Disable branch generation in nVHE guests Rob Herring (Arm)
2025-02-03 9:16 ` Anshuman Khandual
2025-02-03 11:28 ` James Clark
2025-02-13 17:03 ` Leo Yan
2025-02-13 23:16 ` Rob Herring
2025-02-14 9:55 ` Leo Yan
2025-02-18 14:17 ` Rob Herring
2025-02-03 0:43 ` [PATCH v19 11/11] perf: arm_pmuv3: Add support for the Branch Record Buffer Extension (BRBE) Rob Herring (Arm)
2025-02-03 16:53 ` James Clark
2025-02-03 17:58 ` Rob Herring
2025-02-04 12:02 ` James Clark
2025-02-04 15:03 ` Rob Herring
2025-02-05 14:38 ` James Clark
2025-02-05 14:51 ` James Clark
2025-02-05 16:15 ` Rob Herring
2025-02-06 12:58 ` James Clark
2025-02-12 18:52 ` Leo Yan
2025-02-12 19:00 ` Leo Yan
2025-02-13 16:16 ` Leo Yan
2025-02-13 17:13 ` Rob Herring
2025-02-13 17:45 ` Leo Yan
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