[PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

[PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

[Lu Baolu]

Address field in device TLB invalidation descriptor is qualified
by the S field. If S field is zero, a single page at page address
specified by address [63:12] is requested to be invalidated. If S
field is set, the least significant bit in the address field with
value 0b (say bit N) indicates the invalidation address range. The
spec doesn't require the address [N - 1, 0] to be cleared, hence
remove the unnecessary WARN_ON_ONCE().

Otherwise, the caller might set "mask = MAX_AGAW_PFN_WIDTH" in order
to invalidating all the cached mappings on an endpoint, and below
overflow error will be triggered.

[...]
UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1354:3
shift exponent 64 is too large for 64-bit type 'long long unsigned int'
[...]

Reported-and-tested-by: Frank <fgndev@posteo.de>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/dmar.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 613b7153905d..071bb42bbbc5 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1354,7 +1354,6 @@ void qi_flush_dev_iotlb(struct intel_iommu *iommu, u16 sid, u16 pfsid,
 	struct qi_desc desc;
 
 	if (mask) {
-		WARN_ON_ONCE(addr & ((1ULL << (VTD_PAGE_SHIFT + mask)) - 1));
 		addr |= (1ULL << (VTD_PAGE_SHIFT + mask - 1)) - 1;
 		desc.qw1 = QI_DEV_IOTLB_ADDR(addr) | QI_DEV_IOTLB_SIZE;
 	} else
-- 
2.17.1

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Re: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

[Joerg Roedel]

On Thu, Jan 16, 2020 at 09:52:36AM +0800, Lu Baolu wrote:
> Address field in device TLB invalidation descriptor is qualified
> by the S field. If S field is zero, a single page at page address
> specified by address [63:12] is requested to be invalidated. If S
> field is set, the least significant bit in the address field with
> value 0b (say bit N) indicates the invalidation address range. The
> spec doesn't require the address [N - 1, 0] to be cleared, hence
> remove the unnecessary WARN_ON_ONCE().
> 
> Otherwise, the caller might set "mask = MAX_AGAW_PFN_WIDTH" in order
> to invalidating all the cached mappings on an endpoint, and below
> overflow error will be triggered.
> 
> [...]
> UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1354:3
> shift exponent 64 is too large for 64-bit type 'long long unsigned int'
> [...]
> 
> Reported-and-tested-by: Frank <fgndev@posteo.de>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>

Does this need a Fixes and/or stable tag?


Regards,

	Joerg

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Re: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

[Lu Baolu]

Hi Joerg,

On 1/17/20 5:59 PM, Joerg Roedel wrote:
> On Thu, Jan 16, 2020 at 09:52:36AM +0800, Lu Baolu wrote:
>> Address field in device TLB invalidation descriptor is qualified
>> by the S field. If S field is zero, a single page at page address
>> specified by address [63:12] is requested to be invalidated. If S
>> field is set, the least significant bit in the address field with
>> value 0b (say bit N) indicates the invalidation address range. The
>> spec doesn't require the address [N - 1, 0] to be cleared, hence
>> remove the unnecessary WARN_ON_ONCE().
>>
>> Otherwise, the caller might set "mask = MAX_AGAW_PFN_WIDTH" in order
>> to invalidating all the cached mappings on an endpoint, and below
>> overflow error will be triggered.
>>
>> [...]
>> UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1354:3
>> shift exponent 64 is too large for 64-bit type 'long long unsigned int'
>> [...]
>>
>> Reported-and-tested-by: Frank <fgndev@posteo.de>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> 
> Does this need a Fixes and/or stable tag?
> 

This doesn't cause any errors, just an unnecessary checking of

	"0 & ((1UL << 64) - 1)"

in some cases.

> 
> Regards,
> 
> 	Joerg

Best regards,
baolu
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Re: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

[Joerg Roedel]

On Sat, Jan 18, 2020 at 10:14:11AM +0800, Lu Baolu wrote:
> Hi Joerg,
> 
> On 1/17/20 5:59 PM, Joerg Roedel wrote:
> > On Thu, Jan 16, 2020 at 09:52:36AM +0800, Lu Baolu wrote:
> > > Address field in device TLB invalidation descriptor is qualified
> > > by the S field. If S field is zero, a single page at page address
> > > specified by address [63:12] is requested to be invalidated. If S
> > > field is set, the least significant bit in the address field with
> > > value 0b (say bit N) indicates the invalidation address range. The
> > > spec doesn't require the address [N - 1, 0] to be cleared, hence
> > > remove the unnecessary WARN_ON_ONCE().
> > > 
> > > Otherwise, the caller might set "mask = MAX_AGAW_PFN_WIDTH" in order
> > > to invalidating all the cached mappings on an endpoint, and below
> > > overflow error will be triggered.
> > > 
> > > [...]
> > > UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1354:3
> > > shift exponent 64 is too large for 64-bit type 'long long unsigned int'
> > > [...]
> > > 
> > > Reported-and-tested-by: Frank <fgndev@posteo.de>
> > > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> > 
> > Does this need a Fixes and/or stable tag?
> > 
> 
> This doesn't cause any errors, just an unnecessary checking of
> 
> 	"0 & ((1UL << 64) - 1)"
> 
> in some cases.

Okay, applied for v5.6.
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