On 15/08/2024 23:16, Shanker Donthineni wrote:

Hi Steven,

On 7/12/24 03:54, Matias Ezequiel Vara Larsen wrote:

quoted

On Mon, Jul 01, 2024 at 10:54:50AM +0100, Steven Price wrote:

quoted

This series adds support for running Linux in a protected VM under the
Arm Confidential Compute Architecture (CCA). This has been updated
following the feedback from the v3 posting[1]. Thanks for the feedback!
Individual patches have a change log. But things to highlight:

  * a new patch ("firmware/psci: Add psci_early_test_conduit()") to
    prevent SMC calls being made on systems which don't support them -
    i.e. systems without EL2/EL3 - thanks Jean-Philippe!

  * two patches dropped (overriding set_fixmap_io). Instead
    FIXMAP_PAGE_IO is modified to include PROT_NS_SHARED. When support
    for assigning hardware devices to a realm guest is added this will
    need to be brought back in some form. But for now it's just adding
    complixity and confusion for no gain.

  * a new patch ("arm64: mm: Avoid TLBI when marking pages as valid")
    which avoids doing an extra TLBI when doing the break-before-make.
    Note that this changes the behaviour in other cases when making
    memory valid. This should be safe (and saves a TLBI for those
cases),
    but it's a separate patch in case of regressions.

  * GIC ITT allocation now uses a custom genpool-based allocator. I
    expect this will be replaced with a generic way of allocating
    decrypted memory (see [4]), but for now this gets things working
    without wasting too much memory.

The ABI to the RMM from a realm (the RSI) is based on the final RMM v1.0
(EAC 5) specification[2]. Future RMM specifications will be backwards
compatible so a guest using the v1.0 specification (i.e. this series)
will be able to run on future versions of the RMM without modification.

This series is based on v6.10-rc1. It is also available as a git
repository:

https://gitlab.arm.com/linux-arm/linux-cca cca-guest/v4

Which cca-host branch should I use for testing cca-guest/v4?

I'm getting compilation errors with cca-host/v3 and cca-guest/v4, is there
any known WAR or fix to resolve this issue?

cca-host/v3 should work with cca-guest/v4. I've been working on
rebasing/updating the branches and should be able to post v4/v5 series
next week.

arch/arm64/kvm/rme.c: In function ‘kvm_realm_reset_id_aa64dfr0_el1’:
././include/linux/compiler_types.h:487:45: error: call to
‘__compiletime_assert_650’ declared with attribute error: FIELD_PREP:
value too large for the field
  487 |         _compiletime_assert(condition, msg,
__compiletime_assert_, __COUNTER__)
      |                                             ^
././include/linux/compiler_types.h:468:25: note: in definition of macro
‘__compiletime_assert’
  468 |                         prefix ##
suffix();                             \
      |                         ^~~~~~
././include/linux/compiler_types.h:487:9: note: in expansion of macro
‘_compiletime_assert’
  487 |         _compiletime_assert(condition, msg,
__compiletime_assert_, __COUNTER__)
      |         ^~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:37: note: in expansion of macro
‘compiletime_assert’
   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond),
msg)
      |                                     ^~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:68:17: note: in expansion of macro
‘BUILD_BUG_ON_MSG’
   68 |                 BUILD_BUG_ON_MSG(__builtin_constant_p(_val)
?           \
      |                 ^~~~~~~~~~~~~~~~
./include/linux/bitfield.h:115:17: note: in expansion of macro
‘__BF_FIELD_CHECK’
  115 |                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP:
");    \
      |                 ^~~~~~~~~~~~~~~~
arch/arm64/kvm/rme.c:315:16: note: in expansion of macro ‘FIELD_PREP’
  315 |         val |= FIELD_PREP(ID_AA64DFR0_EL1_BRPs_MASK, bps - 1) |
      |                ^~~~~~~~~~
make[5]: *** [scripts/Makefile.build:244: arch/arm64/kvm/rme.o] Error 1
make[4]: *** [scripts/Makefile.build:485: arch/arm64/kvm] Error 2
make[3]: *** [scripts/Makefile.build:485: arch/arm64] Error 2
make[3]: *** Waiting for unfinished jobs....

I'm using gcc-13.3.0 compiler and cross-compiling on X86 machine.

I'm not sure quite how this happens. The 'value' (bps - 1) shouldn't be
considered constant, so I don't see how the compiler has decided to
complain here - the __builtin_constant_p() should really be evaluating to 0.

The only thing I can think of is if the compiler has somehow determined
that rmm_feat_reg0 is 0 - which in theory it could do if it knew that
kvm_init_rme() cannot succeed (rmi_features() would never be called, so
the variable will never be set). Which makes me wonder if you're
building with a PAGE_SIZE other than 4k?

Obviously the code should still build if that's the case (so this would
be a bug) but we don't currently support CCA with PAGE_SIZE != 4k.

Steve