The current process does not enable the bypass setting regardless of
the value of the disable_bypass module parameter when ACPI is enabled,
so the value of the disable_bypass module parameter has been corrected
so that it is handled correctly.
Signed-off-by: Shuuichirou Ishii <[email protected]>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 88817a3376ef..256d7b2a83a7 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3396,7 +3396,7 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
/* Enable the SMMU interface, or ensure bypass */
- if (!bypass || disable_bypass) {
+ if (!bypass && disable_bypass) {
enables |= CR0_SMMUEN;
} else {
ret = arm_smmu_update_gbpa(smmu, 0, GBPA_ABORT);
--
2.27.0
On 2022-08-03 00:42, Shuuichirou Ishii wrote:
> The current process does not enable the bypass setting regardless of
> the value of the disable_bypass module parameter when ACPI is enabled,
> so the value of the disable_bypass module parameter has been corrected
> so that it is handled correctly.
>
> Signed-off-by: Shuuichirou Ishii <[email protected]>
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 88817a3376ef..256d7b2a83a7 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -3396,7 +3396,7 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
> enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
>
> /* Enable the SMMU interface, or ensure bypass */
> - if (!bypass || disable_bypass) {
> + if (!bypass && disable_bypass) {
This change looks obviously wrong - if bypass is false here then we
definitely want to enable the SMMU, so disable_bypass is irrelevant. It
shouldn't even be possible to get here with bypass==true under ACPI,
since arm_smmu_device_acpi_probe() cannot fail :/
Robin.
> enables |= CR0_SMMUEN;
> } else {
> ret = arm_smmu_update_gbpa(smmu, 0, GBPA_ABORT);
Hi, Robin,
Thank you for your comments.
> > /* Enable the SMMU interface, or ensure bypass */
> > - if (!bypass || disable_bypass) {
> > + if (!bypass && disable_bypass) {
>
> This change looks obviously wrong - if bypass is false here then we definitely
> want to enable the SMMU, so disable_bypass is irrelevant. It shouldn't even be
> possible to get here with bypass==true under ACPI, since
> arm_smmu_device_acpi_probe() cannot fail :/
Sorry, my understanding of the meaning of the disable_bypass module parameter
and the process of setting GBPA_ABORT was insufficient.
I misunderstood that the disable_bypass module parameter is used to simply
bypass (disable) SMMU (SMMU_CR0.SMMUEN == 0 and SMMU_GBPA.ABORT == 0).
Forget about the fixes in this patch.
Although our understanding was lacking,
we thought it would be a good idea to have a module parameter that simply disables SMMU,
so we were considering a fix.
Best regards,
Shuuichirou.
> -----Original Message-----
> From: Robin Murphy <[email protected]>
> Sent: Wednesday, August 3, 2022 6:26 PM
> To: Ishii, Shuuichirou/石井 周一郎 <[email protected]>;
> [email protected]; [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]
> Subject: Re: [PATCH] iommu/arm-smmu-v3: fixed check process for
> disable_bypass module parameter
>
> On 2022-08-03 00:42, Shuuichirou Ishii wrote:
> > The current process does not enable the bypass setting regardless of
> > the value of the disable_bypass module parameter when ACPI is enabled,
> > so the value of the disable_bypass module parameter has been corrected
> > so that it is handled correctly.
> >
> > Signed-off-by: Shuuichirou Ishii <[email protected]>
> > ---
> > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > index 88817a3376ef..256d7b2a83a7 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -3396,7 +3396,7 @@ static int arm_smmu_device_reset(struct
> arm_smmu_device *smmu, bool bypass)
> > enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
> >
> > /* Enable the SMMU interface, or ensure bypass */
> > - if (!bypass || disable_bypass) {
> > + if (!bypass && disable_bypass) {
>
> This change looks obviously wrong - if bypass is false here then we definitely
> want to enable the SMMU, so disable_bypass is irrelevant. It shouldn't even be
> possible to get here with bypass==true under ACPI, since
> arm_smmu_device_acpi_probe() cannot fail :/
> Robin.
>
> > enables |= CR0_SMMUEN;
> > } else {
> > ret = arm_smmu_update_gbpa(smmu, 0, GBPA_ABORT);
On 2022-08-03 13:45, [email protected] wrote:
> Hi, Robin,
> Thank you for your comments.
>
>>> /* Enable the SMMU interface, or ensure bypass */
>>> - if (!bypass || disable_bypass) {
>>> + if (!bypass && disable_bypass) {
>>
>> This change looks obviously wrong - if bypass is false here then we definitely
>> want to enable the SMMU, so disable_bypass is irrelevant. It shouldn't even be
>> possible to get here with bypass==true under ACPI, since
>> arm_smmu_device_acpi_probe() cannot fail :/
>
> Sorry, my understanding of the meaning of the disable_bypass module parameter
> and the process of setting GBPA_ABORT was insufficient.
>
> I misunderstood that the disable_bypass module parameter is used to simply
> bypass (disable) SMMU (SMMU_CR0.SMMUEN == 0 and SMMU_GBPA.ABORT == 0).
> Forget about the fixes in this patch.
>
> Although our understanding was lacking,
> we thought it would be a good idea to have a module parameter that simply disables SMMU,
> so we were considering a fix.
Right, disable_bypass is a security/robustness feature for when the
driver *is* in use. If for some reason you want to disable the SMMU
drivers completely, they are regular driver model drivers, so just don't
load the module in the first place (or use initcall_blacklist if it's
built-in).
Thanks,
Robin.
>
> Best regards,
> Shuuichirou.
>
>> -----Original Message-----
>> From: Robin Murphy <[email protected]>
>> Sent: Wednesday, August 3, 2022 6:26 PM
>> To: Ishii, Shuuichirou/石井 周一郎 <[email protected]>;
>> [email protected]; [email protected]; [email protected]; [email protected];
>> [email protected]; [email protected]; [email protected];
>> [email protected]; [email protected];
>> [email protected]; [email protected];
>> [email protected]
>> Subject: Re: [PATCH] iommu/arm-smmu-v3: fixed check process for
>> disable_bypass module parameter
>>
>> On 2022-08-03 00:42, Shuuichirou Ishii wrote:
>>> The current process does not enable the bypass setting regardless of
>>> the value of the disable_bypass module parameter when ACPI is enabled,
>>> so the value of the disable_bypass module parameter has been corrected
>>> so that it is handled correctly.
>>>
>>> Signed-off-by: Shuuichirou Ishii <[email protected]>
>>> ---
>>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> index 88817a3376ef..256d7b2a83a7 100644
>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> @@ -3396,7 +3396,7 @@ static int arm_smmu_device_reset(struct
>> arm_smmu_device *smmu, bool bypass)
>>> enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
>>>
>>> /* Enable the SMMU interface, or ensure bypass */
>>> - if (!bypass || disable_bypass) {
>>> + if (!bypass && disable_bypass) {
>>
>> This change looks obviously wrong - if bypass is false here then we definitely
>> want to enable the SMMU, so disable_bypass is irrelevant. It shouldn't even be
>> possible to get here with bypass==true under ACPI, since
>> arm_smmu_device_acpi_probe() cannot fail :/
>> Robin.
>>
>>> enables |= CR0_SMMUEN;
>>> } else {
>>> ret = arm_smmu_update_gbpa(smmu, 0, GBPA_ABORT);