From: Mark Brown <broonie@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, will@kernel.org,
catalin.marinas@arm.com, mark.rutland@arm.com,
James Clark <james.clark@arm.com>, Rob Herring <robh@kernel.org>,
Marc Zyngier <maz@kernel.org>,
Suzuki Poulose <suzuki.poulose@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
linux-perf-users@vger.kernel.org
Subject: Re: [PATCH V9 00/10] arm64/perf: Enable branch stack sampling
Date: Thu, 23 Mar 2023 12:54:29 +0000 [thread overview]
Message-ID: <4d93a3de-c86d-454b-8a43-b24e62ea3be7@sirena.org.uk> (raw)
In-Reply-To: <f7e24b0c-3e33-755a-65c9-2ee78d5a79ec@arm.com>
[-- Attachment #1: Type: text/plain, Size: 1683 bytes --]
On Thu, Mar 23, 2023 at 09:55:47AM +0530, Anshuman Khandual wrote:
> On 3/22/23 00:32, Mark Brown wrote:
> > document a requirement for those traps to be disabled now in case we
> > need them later, and do so during EL2 setup for KVM guests? That could
> > always be done incrementally.
> Unlike all other instruction trap enable fields in SYS_HFGITR_EL2, these BRBE
> instructions ones are actually inverted in semantics i.e the particular fields
> need to be set for these traps to be disabled in EL2.
Right, for backwards compatibility all newly added fields are trap by
default.
> SYS_HFGITR_EL2.nBRBIALL
> SYS_HFGITR_EL2.nBRBINJ
> By default entire SYS_HFGITR_EL2 is set as cleared during init and that would
> prevent a guest from using BRBE.
It should prevent the host as well shouldn't it?
> I guess something like the following (untested) needs to be done, to enable
> BRBE in guests.
> + mrs x1, id_aa64dfr0_el1
> + ubfx x1, x1, #ID_AA64DFR0_EL1_BRBE_SHIFT, #4
> + cbz x1, .Lskip_brbe_\@
> + mov x0, xzr
> + orr x0, x0, #HFGITR_EL2_nBRBIALL
> + orr x0, x0, #HFGITR_EL2_nBRBINJ
> + msr_s SYS_HFGITR_EL2, x0
> +
> +.Lskip_brbe_\@:
Yes, looks roughly what I'd expect.
> > I've got a patch adding the definition of that register to sysreg which
> > I should be sending shortly, no need to duplicate that effort.
> Sure, I assume you are moving the existing definition for SYS_HFGITR_EL2 along
> with all its fields from ../include/asm/sysreg.h to ../tools/sysreg. Right, it
> makes sense.
No fields at the minute but yes, like the other conversions.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2023-03-23 12:54 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-15 5:14 [PATCH V9 00/10] arm64/perf: Enable branch stack sampling Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 01/10] drivers: perf: arm_pmu: Add new sched_task() callback Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 02/10] arm64/perf: Add BRBE registers and fields Anshuman Khandual
2023-04-12 8:32 ` Yang Shen
2023-05-15 6:22 ` Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 03/10] arm64/perf: Add branch stack support in struct arm_pmu Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 04/10] arm64/perf: Add branch stack support in struct pmu_hw_events Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 05/10] arm64/perf: Add branch stack support in ARMV8 PMU Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 06/10] arm64/perf: Enable branch stack events via FEAT_BRBE Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 07/10] arm64/perf: Add PERF_ATTACH_TASK_DATA to events with has_branch_stack() Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 08/10] arm64/perf: Add struct brbe_regset helper functions Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 09/10] arm64/perf: Implement branch records save on task sched out Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 10/10] arm64/perf: Implement branch records save on PMU IRQ Anshuman Khandual
2023-05-23 14:39 ` James Clark
2023-05-23 14:51 ` James Clark
2023-05-24 3:10 ` Anshuman Khandual
2023-03-21 19:02 ` [PATCH V9 00/10] arm64/perf: Enable branch stack sampling Mark Brown
2023-03-23 4:25 ` Anshuman Khandual
2023-03-23 12:54 ` Mark Brown [this message]
2023-03-24 3:20 ` Anshuman Khandual
2023-03-24 11:40 ` Mark Brown
2023-04-11 13:03 ` Will Deacon
2023-05-15 6:24 ` Anshuman Khandual
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4d93a3de-c86d-454b-8a43-b24e62ea3be7@sirena.org.uk \
--to=broonie@kernel.org \
--cc=acme@kernel.org \
--cc=anshuman.khandual@arm.com \
--cc=catalin.marinas@arm.com \
--cc=james.clark@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=robh@kernel.org \
--cc=suzuki.poulose@arm.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).