1. 11 Jul, 2023 1 commit
    • Marc Zyngier's avatar
      KVM: arm64: timers: Use CNTHCTL_EL2 when setting non-CNTKCTL_EL1 bits · fe769e6c
      Marc Zyngier authored
      It recently appeared that, when running VHE, there is a notable
      difference between using CNTKCTL_EL1 and CNTHCTL_EL2, despite what
      the architecture documents:
      
      - When accessed from EL2, bits [19:18] and [16:10] of CNTKCTL_EL1 have
        the same assignment as CNTHCTL_EL2
      - When accessed from EL1, bits [19:18] and [16:10] are RES0
      
      It is all OK, until you factor in NV, where the EL2 guest runs at EL1.
      In this configuration, CNTKCTL_EL11 doesn't trap, nor ends up in
      the VNCR page. This means that any write from the guest affecting
      CNTHCTL_EL2 using CNTKCTL_EL1 ends up losing some state. Not good.
      
      The fix it obvious: don't use CNTKCTL_EL1 if you want to change bits
      that are not part of the EL1 definition of CNTKCTL_EL1, and use
      CNTHCTL_EL2 instead. This doesn't change anything for a bare-metal OS,
      and fixes it when running under NV. The NV hypervisor will itself
      have to work harder to merge the two accessors.
      
      Note that there is a pending update to the architecture to address
      this issue by making the affected bits UNKNOWN when CNTKCTL_EL1 is
      used from EL2 with VHE enabled.
      
      Fixes: c605ee24 ("KVM: arm64: timers: Allow physical offset without CNTPOFF_EL2")
      Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
      Cc: stable@vger.kernel.org # v6.4
      Reviewed-by: default avatarEric Auger <eric.auger@redhat.com>
      Link: https://lore.kernel.org/r/20230627140557.544885-1-maz@kernel.orgSigned-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
      fe769e6c
  2. 09 Jul, 2023 10 commits
  3. 08 Jul, 2023 29 commits