Re: [PATCH v3 18/18] arm64: Kill PSCI_GET_VERSION as a variant-2 workaround

[Marc Zyngier]

On 02/02/18 04:05, Hanjun Guo wrote:
> Hi Marc,
> 
> Thank you for keeping me in the loop, just minor comments below.
> 
> On 2018/2/1 19:46, Marc Zyngier wrote:
>> Now that we've standardised on SMCCC v1.1 to perform the branch
>> prediction invalidation, let's drop the previous band-aid.
>> If vendors haven't updated their firmware to do SMCCC 1.1, they
>> haven't updated PSCI either, so we don't loose anything.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>> ---
>>  arch/arm64/kernel/bpi.S        | 24 -----------------------
>>  arch/arm64/kernel/cpu_errata.c | 43 ++++++++++++------------------------------
>>  arch/arm64/kvm/hyp/switch.c    | 14 --------------
>>  3 files changed, 12 insertions(+), 69 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S
>> index fdeed629f2c6..e5de33513b5d 100644
>> --- a/arch/arm64/kernel/bpi.S
>> +++ b/arch/arm64/kernel/bpi.S
>> @@ -54,30 +54,6 @@ ENTRY(__bp_harden_hyp_vecs_start)
>>  	vectors __kvm_hyp_vector
>>  	.endr
>>  ENTRY(__bp_harden_hyp_vecs_end)
>> -ENTRY(__psci_hyp_bp_inval_start)
>> -	sub	sp, sp, #(8 * 18)
>> -	stp	x16, x17, [sp, #(16 * 0)]
>> -	stp	x14, x15, [sp, #(16 * 1)]
>> -	stp	x12, x13, [sp, #(16 * 2)]
>> -	stp	x10, x11, [sp, #(16 * 3)]
>> -	stp	x8, x9, [sp, #(16 * 4)]
>> -	stp	x6, x7, [sp, #(16 * 5)]
>> -	stp	x4, x5, [sp, #(16 * 6)]
>> -	stp	x2, x3, [sp, #(16 * 7)]
>> -	stp	x0, x1, [sp, #(16 * 8)]
>> -	mov	x0, #0x84000000
>> -	smc	#0
>> -	ldp	x16, x17, [sp, #(16 * 0)]
>> -	ldp	x14, x15, [sp, #(16 * 1)]
>> -	ldp	x12, x13, [sp, #(16 * 2)]
>> -	ldp	x10, x11, [sp, #(16 * 3)]
>> -	ldp	x8, x9, [sp, #(16 * 4)]
>> -	ldp	x6, x7, [sp, #(16 * 5)]
>> -	ldp	x4, x5, [sp, #(16 * 6)]
>> -	ldp	x2, x3, [sp, #(16 * 7)]
>> -	ldp	x0, x1, [sp, #(16 * 8)]
>> -	add	sp, sp, #(8 * 18)
>> -ENTRY(__psci_hyp_bp_inval_end)
>>  
>>  ENTRY(__qcom_hyp_sanitize_link_stack_start)
>>  	stp     x29, x30, [sp, #-16]!
>> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
>> index 9e77809a3b23..b8279a11f57b 100644
>> --- a/arch/arm64/kernel/cpu_errata.c
>> +++ b/arch/arm64/kernel/cpu_errata.c
>> @@ -67,7 +67,6 @@ static int cpu_enable_trap_ctr_access(void *__unused)
>>  DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
>>  
>>  #ifdef CONFIG_KVM
>> -extern char __psci_hyp_bp_inval_start[], __psci_hyp_bp_inval_end[];
>>  extern char __qcom_hyp_sanitize_link_stack_start[];
>>  extern char __qcom_hyp_sanitize_link_stack_end[];
>>  extern char __smccc_workaround_1_smc_start[];
>> @@ -116,8 +115,6 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
>>  	spin_unlock(&bp_lock);
>>  }
>>  #else
>> -#define __psci_hyp_bp_inval_start		NULL
>> -#define __psci_hyp_bp_inval_end			NULL
>>  #define __qcom_hyp_sanitize_link_stack_start	NULL
>>  #define __qcom_hyp_sanitize_link_stack_end	NULL
>>  #define __smccc_workaround_1_smc_start		NULL
>> @@ -164,14 +161,15 @@ static void call_hvc_arch_workaround_1(void)
>>  	arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
>>  }
>>  
>> -static bool check_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
>> +static int smccc_arch_workaround_1(void *data)
>>  {
>> +	const struct arm64_cpu_capabilities *entry = data;
>>  	bp_hardening_cb_t cb;
>>  	void *smccc_start, *smccc_end;
>>  	struct arm_smccc_res res;
>>  
>>  	if (!entry->matches(entry, SCOPE_LOCAL_CPU))
> 
> entry->matches() will be called twice in this function, another
> one is in install_bp_hardening_cb() below, but install_bp_hardening_cb()
> will be called in qcom_enable_link_stack_sanitization(), and
> this is in the init path, so I think it's fine to keep as it is now.

That's on purpose. Otherwise we spam the firmware/hypervisor with probe
calls for each entry that has the same capability. Not a big deal, but
still. This should be addressed when we get Suzuki's rework.

> 
>> -		return false;
>> +		return 0;
>>  
>>  	if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
>>  		return false;
> 
> return 0;

Ah, indeed. Thanks.

	M.
-- 
Jazz is not dead. It just smells funny...