[PATCH 0/7] arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9

[Rob Herring]

On Tue, Jan 7, 2025 at 6:13 AM Catalin Marinas <catalin.marinas at arm.com> wrote:
>
> On Thu, Jan 02, 2025 at 10:04:02AM -0600, Rob Herring wrote:
> > On Fri, Dec 20, 2024 at 12:52:33PM +0530, Anshuman Khandual wrote:
> > > This series adds fine grained trap control in EL2 required for FEAT_PMUv3p9
> > > registers like PMICNTR_EL0, PMICFILTR_EL0, and PMUACR_EL1 which are already
> > > being used in the kernel. This is required to prevent their EL1 access trap
> > > into EL2.
> > >
> > > PMZR_EL0 register trap control i.e HDFGWTR2_EL2.nPMZR_EL0 remains unchanged
> > > for now as it does not get accessed in the kernel, and there is no plan for
> > > its access from user space.
> > >
> > > I have taken the liberty to pick up all the review tags for patches related
> > > to tools sysreg update from the KVM FGT2 V2 patch series posted earlier.
> > >
> > > https://lore.kernel.org/all/20241210055311.780688-1-anshuman.khandual@arm.com/
> > >
> > > Rob had earler mentioned about FEAT_FGT2 based trap control requirement for
> > > FEAT_PMUv3p9 registers that are currently being used in kernel. The context
> > > can be found here.
> > >
> > > https://lore.kernel.org/all/20241216234251.GA629562-robh@kernel.org/
> > >
> > > This series is based on v6.13-rc3
> > >
> > > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > > Cc: Will Deacon <will at kernel.org>
> > > Cc: Marc Zyngier <maz at kernel.org>
> > > Cc: Ryan Roberts <ryan.roberts at arm.com>
> > > Cc: Mark Rutland <mark.rutland at arm.com>
> > > Cc: Mark Brown <robh at kernel.org>
> > > Cc: Rob Herring <robh at kernel.org>
> > > Cc: Oliver Upton <oliver.upton at linux.dev>
> > > Cc: Jonathan Corbet <corbet at lwn.net>
> > > Cc: Eric Auger <eric.auger at redhat.com>
> > > Cc: kvmarm at lists.linux.dev
> > > Cc: linux-doc at vger.kernel.org
> > > Cc: linux-kernel at vger.kernel.org
> > > Cc: linux-arm-kernel at lists.infradead.org
> > >
> > > Anshuman Khandual (7):
> > >   arm64/sysreg: Update register fields for ID_AA64MMFR0_EL1
> > >   arm64/sysreg: Add register fields for HDFGRTR2_EL2
> > >   arm64/sysreg: Add register fields for HDFGWTR2_EL2
> > >   arm64/sysreg: Add register fields for HFGITR2_EL2
> > >   arm64/sysreg: Add register fields for HFGRTR2_EL2
> > >   arm64/sysreg: Add register fields for HFGWTR2_EL2
> > >   arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9
> >
> > In case it is not clear, this series should be applied to 6.13 as the 2
> > PMUv3p9 features already landed in 6.13 (per counter EL0 control) and
> > 6.12 (ICNTR).
>
> So is this a fix that needs backporting to 6.12 or 6.13, e.g. fix for
> d8226d8cfbaf ("perf: arm_pmuv3: Add support for Armv9.4 PMU instruction
> counter")? It's pretty late in the cycle to take the series for 6.13.

Ideally, yes. But given the state of h/w implementations, backporting
it later is probably fine if that is your preference.

> But does KVM actually expose the feature to EL1 in ID_AA64DFR1_EL1 and
> than traps it at EL2?

As Marc pointed out KVM only advertises PMUv3.8. Regardless, guest
accesses to these registers are trapped with or without this series.

Rob