Although support for SME was merged in v5.19, we've since uncovered a number of issues with the implementation, including issues which might corrupt the FPSIMD/SVE/SME state of arbitrary tasks. While there are patches to address some of these issues, ongoing review has highlighted additional functional problems, and more time is necessary to analyse and fix these.
For now, mark SME as BROKEN in the hope that we can fix things properly in the near future. As SME is an OPTIONAL part of ARMv9.2+, and there is very little extant hardware, this should not adversely affect the vast majority of users.
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Ard Biesheuvel ardb@kernel.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Marc Zyngier maz@kernel.org Cc: Mark Brown broonie@kernel.org Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org # 5.19 --- arch/arm64/Kconfig | 1 + 1 file changed, 1 insertion(+)
Catalin, Will, if we take this, the minimal set of other fixes necessary for now is:
* "arm64/sve: Discard stale CPU state when handling SVE traps" https://lore.kernel.org/linux-arm-kernel/20241030-arm64-fpsimd-foreign-flush... https://lore.kernel.org/linux-arm-kernel/ZypuQNhWHKut8mLl@J2N7QTR9R3.cambrid... (already queued by Will in for-next/fixes)
* "arm64: smccc: Remove broken support for SMCCCv1.3 SVE discard hint" https://lore.kernel.org/linux-arm-kernel/20241106160448.2712997-1-mark.rutla...
Mark.
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 3e29b44d2d7bd..14cc81e154ee2 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -2213,6 +2213,7 @@ config ARM64_SME bool "ARM Scalable Matrix Extension support" default y depends on ARM64_SVE + depends on BROKEN help The Scalable Matrix Extension (SME) is an extension to the AArch64 execution state which utilises a substantial subset of the SVE
On Wed, Nov 06, 2024 at 04:42:20PM +0000, Mark Rutland wrote:
Although support for SME was merged in v5.19, we've since uncovered a number of issues with the implementation, including issues which might corrupt the FPSIMD/SVE/SME state of arbitrary tasks. While there are patches to address some of these issues, ongoing review has highlighted additional functional problems, and more time is necessary to analyse and fix these.
It would be good to start landing some of those as well (and more of the test improvements that are pending as well).
For now, mark SME as BROKEN in the hope that we can fix things properly in the near future. As SME is an OPTIONAL part of ARMv9.2+, and there is very little extant hardware, this should not adversely affect the vast majority of users.
It doesn't seem ideal to bounce on and off in stable, though as you say there aren't really any practical systems at the minute and hopefully we can revert this fairly soon.
On Wed, Nov 06, 2024 at 04:42:20PM +0000, Mark Rutland wrote:
Although support for SME was merged in v5.19, we've since uncovered a number of issues with the implementation, including issues which might corrupt the FPSIMD/SVE/SME state of arbitrary tasks. While there are patches to address some of these issues, ongoing review has highlighted additional functional problems, and more time is necessary to analyse and fix these.
For now, mark SME as BROKEN in the hope that we can fix things properly in the near future. As SME is an OPTIONAL part of ARMv9.2+, and there is very little extant hardware, this should not adversely affect the vast majority of users.
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Ard Biesheuvel ardb@kernel.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Marc Zyngier maz@kernel.org Cc: Mark Brown broonie@kernel.org Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org # 5.19
I agree that's the best way forward given the proximity to final 6.12. Let's hope we'll revert it shortly after. Thanks to both you and broonie for continuing to dig into this.
Acked-by: Catalin Marinas catalin.marinas@arm.com
On Wed, 06 Nov 2024 16:42:20 +0000, Mark Rutland wrote:
Although support for SME was merged in v5.19, we've since uncovered a number of issues with the implementation, including issues which might corrupt the FPSIMD/SVE/SME state of arbitrary tasks. While there are patches to address some of these issues, ongoing review has highlighted additional functional problems, and more time is necessary to analyse and fix these.
[...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64: Kconfig: Make SME depend on BROKEN for now https://git.kernel.org/arm64/c/81235ae0c846
Cheers,
linux-stable-mirror@lists.linaro.org
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Catalin Marinas -
Mark Brown -
Mark Rutland -
Will Deacon