Re: [PATCH 0/2] 52-bit VA guest mode ID support

Hi Fuad,
On Fri, Sep 04, 2026 at 09:14:36AM +0100, Fuad Tabba wrote:

On Tue, 25 Aug 2026 at 22:18, Itaru Kitayama [off-list ref] wrote:

quoted

This patch series extends the arm64 KVM selftest framework
to support 52-bit guest virtual address (VA) modes in addition to
the existing 52-bit physical address (PA) configurations.
The motivation is to enable validation of LPA2 guest memory-management
behaviour in configurations that use a 52-bit VA space.
While the selftest framework already supports testing 52-bit PA
configurations, it lacks the ability to exercise guests running with
52-bit virtual addresses, leaving part of the LPA2 functionality untested.

The series adds three 52-bit VA guest modes, but nothing in tree maps
a guest VA high enough to use them. The mode-iterating tests map at a
fixed low GVA, so pgd_index() returns 0 and only the first entry of
the top level is ever used.

What do you expect the modes to catch as they stand? The allocators
already take a minimum GVA, so mapping high in one of those tests
looks like a small change.

I think at least a 4KB page is allocated for the level -1 translation table, 
and entry 0 is populated with a Table descriptor pointing to the level 0 translation
table. But, no it does not test a nonzero top-level index.

quoted

To address this, the series introduces new guest modes for 52-bit VA
operation, adds five-level page table support where required, and
performs runtime detection of host 52-bit VA capability so that
LPA2-enabled guest VA tests are executed only on supported systems.

Testing:

Built and tested on arm64.
Verified on QEMU with a V52-capable guest configuration.
Confirmed correct operation of high virtual address mappings by
exercising guest memory accesses in the 52-bit VA range.

I could not reproduce "exercising guest memory accesses in the 52-bit
VA range" with anything in tree either. Could you say which test you
ran, which guest modes, and on what?

I just in guest_code() of existing one of the kselftests, mapped and 
accessed a page at 1ULL << 49 using virt_pg_map() and on QEMU TCG mode
as I don't currently have access to the machines LPA and LPA2 features.

Thanks,
Itaru.

Thanks,
/fuad

quoted

Signed-off-by: Itaru Kitayama <redacted>
Reviewed-by: Takayuki Okamoto <redacted>
---
Itaru Kitayama (2):
      KVM: selftest: arm64: Support 5-level paging in stage 1 translation table
      KVM: selftests: arm64: Add 52-bit VA guest modes

 .../selftests/kvm/include/arm64/processor.h        |  2 +
 tools/testing/selftests/kvm/include/kvm_util.h     |  3 +
 tools/testing/selftests/kvm/lib/arm64/processor.c  | 87 ++++++++++++++++++++--
 tools/testing/selftests/kvm/lib/guest_modes.c      |  5 ++
 tools/testing/selftests/kvm/lib/kvm_util.c         | 11 +++
 5 files changed, 103 insertions(+), 5 deletions(-)
---
base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
change-id: 20260825-arm64-52bit-va-32f1f4cd050d

Best regards,
--
Itaru Kitayama [off-list ref]