Attachment 820901 Details for Bug 1139073

TAA-enumeration.txt

TAA-enumeration.txt (text/plain), 977 bytes, created by Marcus Meissner on 2019-10-09 12:31:25 UTC

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Creator: Marcus Meissner

Created: 2019-10-09 12:31:25 UTC

Size: 977 bytes

patch

obsolete

>Enumeration details for OS's and VMMs for TAA
>
>On a running system:
> * Load new microcode at runtime
> * Observe MSR_ARCH_CAPS.TSX_CTRL is now available
>   => Implies VERW now has flushing side effects
> * Set MSR_TSX_CTRL.RTM_DISABLE
> * Existing VMs/userspace must continue to see RTM.
>   => XBEGIN will unconditionally abort
> * New VMs should be levelled as if RTM doesn't exist.
>
>On a fresh boot after TAA hotfix:
> * Load new microcode at boot
> For Native:
>   * Set MSR_TSX_CTRL.{RTM_DISABLE,CPUID_CLEAR}
>     => No further action
> For Virtualised:
>   * Set MSR_TSX_CTRL.RTM_DISABLE
>   * For migrated-in VMs, leave RTM visibility as before
>   * For newly-started VMs, hide RTM
>
>For a VM booting on MDS_NO, non-TAA_NO hardware:
> * RTM may be levelled out of the pool, as may MDS_NO
> * MD_CLEAR may be enumerated even if it behaves as a nop
>
>Questions to other vendors:
> * [VMM] Do you plan to offer MSR_TSX_CTRL to guests?
> * [OS]  Do you plan to use per-process TSX settings?

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