| Message ID | 20231212170910.3745497-1-mark.rutland@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | arm64: cpucap handling cleanups | expand |
On Tue, 12 Dec 2023 17:09:08 +0000, Mark Rutland wrote: > The recent changes to remove cpus_have_const_cap() left a period between > detecting cpucaps and patching alternatives where it is necessary to use > cpus_have_cap() to check that a cpucap has been detected. During this > period we do a few things, and there's a risk that code using a mixture > of cpus_have_cap() and alternative_has_cap_*() sees an inconsistent > state. > > [...] Applied to arm64 (for-next/cpufeature), thanks! Basing the series on for-next/fixes makes it fiddly to manage, so I dropped the kpti_install_ng_mappings() hunk from patch 1 and will re-introduce it when I merge the branches together. [1/2] arm64: Cleanup system cpucap handling https://git.kernel.org/arm64/c/63a2d92e1461 [2/2] arm64: Align boot cpucap handling with system cpucap handling https://git.kernel.org/arm64/c/eb15d707c252 Cheers,
On Wed, Dec 13, 2023 at 05:25:18PM +0000, Will Deacon wrote: > On Tue, 12 Dec 2023 17:09:08 +0000, Mark Rutland wrote: > > The recent changes to remove cpus_have_const_cap() left a period between > > detecting cpucaps and patching alternatives where it is necessary to use > > cpus_have_cap() to check that a cpucap has been detected. During this > > period we do a few things, and there's a risk that code using a mixture > > of cpus_have_cap() and alternative_has_cap_*() sees an inconsistent > > state. > > > > [...] > > Applied to arm64 (for-next/cpufeature), thanks! > > Basing the series on for-next/fixes makes it fiddly to manage, so I > dropped the kpti_install_ng_mappings() hunk from patch 1 and will > re-introduce it when I merge the branches together. Thanks, and sorry for the hassle! The changes and resolution in that branch look good to me (and build and boot cleanly); I'll go throw that on my test system and see if anything blows up overnight. Mark. > [1/2] arm64: Cleanup system cpucap handling > https://git.kernel.org/arm64/c/63a2d92e1461 > [2/2] arm64: Align boot cpucap handling with system cpucap handling > https://git.kernel.org/arm64/c/eb15d707c252 > > Cheers, > -- > Will > > https://fixes.arm64.dev > https://next.arm64.dev > https://will.arm64.dev
The recent changes to remove cpus_have_const_cap() left a period between detecting cpucaps and patching alternatives where it is necessary to use cpus_have_cap() to check that a cpucap has been detected. During this period we do a few things, and there's a risk that code using a mixture of cpus_have_cap() and alternative_has_cap_*() sees an inconsistent state. These patches rework the cpucap code to minimize the period between detecting cpucaps and patching the relevant alternatives, deferring other work until after the alternatives have been patched. This removes the need for some code to use cpus_have_cap(), and allows them to use common helper functions that may use alternative_has_cap_*() internally, making them consistent with other kernel code. This cleanup was requested by Will across: https://lore.kernel.org/linux-arm-kernel/20231127154818.GA8453@willie-the-truck/ https://lore.kernel.org/linux-arm-kernel/20231127163103.GA8627@willie-the-truck/ https://lore.kernel.org/linux-arm-kernel/20231127164127.GB8627@willie-the-truck/ https://lore.kernel.org/linux-arm-kernel/20231128110339.GA9717@willie-the-truck/ The patches are based on the arm64 for-next/fixes branch, whose HEAD commit is currently: f5259997f3e8d6ed ("arm64: Avoid enabling KPTI unnecessarily") ... which patch 1 is partially a cleanup for. I've given both patches some testing in a few configurations (e.g. with and without nVHE forced on the command line) to check that detection and patching works as expected. Mark. Mark Rutland (2): arm64: Cleanup system cpucap handling arm64: Align boot cpucap handling with system cpucap handling arch/arm64/include/asm/cpufeature.h | 1 + arch/arm64/kernel/cpufeature.c | 105 +++++++++++++++------------- arch/arm64/kernel/fpsimd.c | 4 +- arch/arm64/kernel/smp.c | 12 +--- 4 files changed, 64 insertions(+), 58 deletions(-)