Re: [PATCH v3 0/3] Off-load TLB invalidations to host for !GTSE

Excerpts from Qian Cai's message of July 17, 2020 3:27 am:

On Fri, Jul 03, 2020 at 11:06:05AM +0530, Bharata B Rao wrote:

quoted

Hypervisor may choose not to enable Guest Translation Shootdown Enable
(GTSE) option for the guest. When GTSE isn't ON, the guest OS isn't
permitted to use instructions like tblie and tlbsync directly, but is
expected to make hypervisor calls to get the TLB flushed.

This series enables the TLB flush routines in the radix code to
off-load TLB flushing to hypervisor via the newly proposed hcall
H_RPT_INVALIDATE. 

To easily check the availability of GTSE, it is made an MMU feature.
The OV5 handling and H_REGISTER_PROC_TBL hcall are changed to
handle GTSE as an optionally available feature and to not assume GTSE
when radix support is available.

The actual hcall implementation for KVM isn't included in this
patchset and will be posted separately.

Changes in v3
=============
- Fixed a bug in the hcall wrapper code where we were missing setting
  H_RPTI_TYPE_NESTED while retrying the failed flush request with
  a full flush for the nested case.
- s/psize_to_h_rpti/psize_to_rpti_pgsize

v2: https://lore.kernel.org/linuxppc-dev/20200626131000.5207-1-bharata@linux.ibm.com/T/#t (local)

Bharata B Rao (2):
  powerpc/mm: Enable radix GTSE only if supported.
  powerpc/pseries: H_REGISTER_PROC_TBL should ask for GTSE only if
    enabled

Nicholas Piggin (1):
  powerpc/mm/book3s64/radix: Off-load TLB invalidations to host when
    !GTSE

Reverting the whole series fixed random memory corruptions during boot on
POWER9 PowerNV systems below.

If I s/mmu_has_feature(MMU_FTR_GTSE)/(1)/g in radix_tlb.c, then the .o
disasm is the same as reverting my patch.

Feature bits not being set right? PowerNV should be pretty simple, seems
to do the same as FTR_TYPE_RADIX.

So... test being done before static keys are set up? Shouldn't be. Must
be something obvious I just can't see it.

Thanks,
Nick