diff options
| author | Will Deacon <will@kernel.org> | 2025-04-07 16:27:55 +0100 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2025-04-07 15:03:34 -0700 |
| commit | a344e258acb0a7f0e7ed10a795c52d1baf705164 (patch) | |
| tree | 0bca97123700c546ea2ebbf066d2979b0f9b8a01 /arch | |
| parent | c8631ea59b6523035ffb607634eef7bacc8947fe (diff) | |
KVM: arm64: Use acquire/release to communicate FF-A version negotiation
The pKVM FF-A proxy rejects FF-A requests other than FFA_VERSION until
version negotiation is complete, which is signalled by setting the
global 'has_version_negotiated' variable.
To avoid excessive locking, this variable is checked directly from
kvm_host_ffa_handler() in response to an FF-A call, but this can race
against another CPU performing the negotiation and potentially lead to
reading a torn value (incredibly unlikely for a 'bool') or problematic
re-ordering of the accesses to 'has_version_negotiated' and
'hyp_ffa_version' whereby a stale version number could be read by
__do_ffa_mem_xfer().
Use acquire/release primitives when writing 'has_version_negotiated'
with the version lock held and when reading without the lock held.
Cc: Sebastian Ene <sebastianene@google.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Quentin Perret <qperret@google.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Marc Zyngier <maz@kernel.org>
Fixes: c9c012625e12 ("KVM: arm64: Trap FFA_VERSION host call in pKVM")
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20250407152755.1041-1-will@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/kvm/hyp/nvhe/ffa.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c index e433dfab882a..3369dd0c4009 100644 --- a/arch/arm64/kvm/hyp/nvhe/ffa.c +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c @@ -730,10 +730,10 @@ static void do_ffa_version(struct arm_smccc_res *res, hyp_ffa_version = ffa_req_version; } - if (hyp_ffa_post_init()) + if (hyp_ffa_post_init()) { res->a0 = FFA_RET_NOT_SUPPORTED; - else { - has_version_negotiated = true; + } else { + smp_store_release(&has_version_negotiated, true); res->a0 = hyp_ffa_version; } unlock: @@ -809,7 +809,8 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id) if (!is_ffa_call(func_id)) return false; - if (!has_version_negotiated && func_id != FFA_VERSION) { + if (func_id != FFA_VERSION && + !smp_load_acquire(&has_version_negotiated)) { ffa_to_smccc_error(&res, FFA_RET_INVALID_PARAMETERS); goto out_handled; } |