On Mon, Feb 10, 2025 at 07:52:18PM +0000, Mark Rutland wrote:
These patches fix some issues with the way KVM manages FPSIMD/SVE/SME state. The series supersedes my earlier attempt at fixing the host SVE state corruption issue:
https://lore.kernel.org/linux-arm-kernel/20250121100026.3974971-1-mark.rutla...
Patch 1 addresses the host SVE state corruption issue by always saving and unbinding the host state when loading a vCPU, as discussed on the earlier patch:
https://lore.kernel.org/linux-arm-kernel/Z4--YuG5SWrP_pW7@J2N7QTR9R3/ https://lore.kernel.org/linux-arm-kernel/86plkful48.wl-maz@kernel.org/
Patches 2 to 4 remove code made redundant by patch 1. These probably warrant backporting along with patch 1 as there is some historical brokenness in the code they remove.
Patches 5 to 7 are preparatory refactoring for patch 8, and are not intended to have any functional impact.
Patch 8 addresses some mismanagement of ZCR_EL{1,2} which can result in the host VMM unexpectedly receiving a SIGKILL. To fix this, we eagerly switch ZCR_EL{1,2} at guest<->host transitions, as discussed on another series:
https://lore.kernel.org/linux-arm-kernel/Z4pAMaEYvdLpmbg2@J2N7QTR9R3/ https://lore.kernel.org/linux-arm-kernel/86o6zzukwr.wl-maz@kernel.org/ https://lore.kernel.org/linux-arm-kernel/Z5Dc-WMu2azhTuMn@J2N7QTR9R3/
The end result is that KVM loses ~100 lines of code, and becomes a bit simpler to reason about.
LGTM, although a minor nitpick would be to repack the host data flags at the end of purging SVE/SME.
Reviewed-by: Oliver Upton oliver.upton@linux.dev