Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] Missing compiler memory barrier causes dead-store elimination and constant-folding of the RSI host call buffer. --
--- Patch [2]: [PATCH v3 2/6] firmware: smccc: Detect hypervisor via RSI host call in CCA Realms --- commit 5f8398cb1bc3327a58d70463ef37d994ffacca02 Author: Kameron Carr <[email protected]> firmware: smccc: Detect hypervisor via RSI host call in CCA Realms This commit modifies arm_smccc_hypervisor_has_uuid() to use rsi_host_call() when operating in a Realm. It introduces arm_smccc_realm_get_hypervisor_uuid() which uses a spinlock-protected file-static buffer to make the call. > diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c > index bdee057db2fd3..a876b7aa2dc99 100644 > --- a/drivers/firmware/smccc/smccc.c > +++ b/drivers/firmware/smccc/smccc.c [ ... ] > @@ -67,12 +73,45 @@ s32 arm_smccc_get_soc_id_revision(void) > } > EXPORT_SYMBOL_GPL(arm_smccc_get_soc_id_revision); > > +#ifdef CONFIG_ARM64 > +static struct rsi_host_call uuid_hc; > +static DEFINE_SPINLOCK(uuid_hc_lock); > + > +/* > + * Helper function to get the hypervisor UUID via an RsiHostCall. > + */ > +static void arm_smccc_realm_get_hypervisor_uuid(struct arm_smccc_res *res) > +{ > + guard(spinlock_irqsave)(&uuid_hc_lock); > + > + memset(&uuid_hc, 0, sizeof(uuid_hc)); > + uuid_hc.gprs[0] = ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID; > + > + if (rsi_host_call(__pa_symbol(&uuid_hc)) != RSI_SUCCESS) { > + res->a0 = SMCCC_RET_NOT_SUPPORTED; > + return; > + } > + > + res->a0 = uuid_hc.gprs[0]; [Severity: High] Does this code need a compiler memory barrier before reading back the results? Because __pa_symbol() uses RELOC_HIDE() to explicitly hide the pointer's provenance from the compiler's alias analysis, the compiler may not realize that rsi_host_call() modifies uuid_hc. Without a barrier(), could the compiler constant-fold the reads to their statically-known previous values? If so, this could result in res->a0 being optimized to ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID instead of the value returned by the hypervisor, and potentially allow the stores during initialization to be dead-store eliminated. > + res->a1 = uuid_hc.gprs[1]; > + res->a2 = uuid_hc.gprs[2]; > + res->a3 = uuid_hc.gprs[3]; > +} > +#endif -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=2
