* [PATCH 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications
@ 2020-08-26 2:58 Lu Baolu
2020-08-26 5:29 ` Tian, Kevin
0 siblings, 1 reply; 3+ messages in thread
From: Lu Baolu @ 2020-08-26 2:58 UTC (permalink / raw)
To: Joerg Roedel; +Cc: iommu, linux-kernel, Lu Baolu, Andy Lutomirski, Jacob Pan
The VT-d spec requires (10.4.4 Global Command Register, GCMD_REG General
Description) that:
If multiple control fields in this register need to be modified, software
must serialize the modifications through multiple writes to this register.
However, in irq_remapping.c, modifications of IRE and CFI are done in one
write. We need to do two separate writes with STS checking after each.
Fixes: af8d102f999a4 ("x86/intel/irq_remapping: Clean up x2apic opt-out security warning mess")
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
drivers/iommu/intel/irq_remapping.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index 9564d23d094f..19d7e18876fe 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -507,12 +507,16 @@ static void iommu_enable_irq_remapping(struct intel_iommu *iommu)
/* Enable interrupt-remapping */
iommu->gcmd |= DMA_GCMD_IRE;
- iommu->gcmd &= ~DMA_GCMD_CFI; /* Block compatibility-format MSIs */
writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
-
IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
readl, (sts & DMA_GSTS_IRES), sts);
+ /* Block compatibility-format MSIs */
+ iommu->gcmd &= ~DMA_GCMD_CFI;
+ writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
+ IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
+ readl, !(sts & DMA_GSTS_CFIS), sts);
+
/*
* With CFI clear in the Global Command register, we should be
* protected from dangerous (i.e. compatibility) interrupts
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* RE: [PATCH 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications
2020-08-26 2:58 [PATCH 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications Lu Baolu
@ 2020-08-26 5:29 ` Tian, Kevin
2020-08-27 4:25 ` Lu Baolu
0 siblings, 1 reply; 3+ messages in thread
From: Tian, Kevin @ 2020-08-26 5:29 UTC (permalink / raw)
To: Lu Baolu, Joerg Roedel; +Cc: iommu, Andy Lutomirski, linux-kernel
> From: Lu Baolu
> Sent: Wednesday, August 26, 2020 10:58 AM
>
> The VT-d spec requires (10.4.4 Global Command Register, GCMD_REG
> General
> Description) that:
>
> If multiple control fields in this register need to be modified, software
> must serialize the modifications through multiple writes to this register.
>
> However, in irq_remapping.c, modifications of IRE and CFI are done in one
> write. We need to do two separate writes with STS checking after each.
>
> Fixes: af8d102f999a4 ("x86/intel/irq_remapping: Clean up x2apic opt-out
> security warning mess")
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel/irq_remapping.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/intel/irq_remapping.c
> b/drivers/iommu/intel/irq_remapping.c
> index 9564d23d094f..19d7e18876fe 100644
> --- a/drivers/iommu/intel/irq_remapping.c
> +++ b/drivers/iommu/intel/irq_remapping.c
> @@ -507,12 +507,16 @@ static void iommu_enable_irq_remapping(struct
> intel_iommu *iommu)
>
> /* Enable interrupt-remapping */
> iommu->gcmd |= DMA_GCMD_IRE;
> - iommu->gcmd &= ~DMA_GCMD_CFI; /* Block compatibility-format
> MSIs */
> writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
> -
> IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
> readl, (sts & DMA_GSTS_IRES), sts);
>
> + /* Block compatibility-format MSIs */
> + iommu->gcmd &= ~DMA_GCMD_CFI;
> + writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
> + IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
> + readl, !(sts & DMA_GSTS_CFIS), sts);
> +
Better do it only when CFI is actually enabled (by checking sts).
> /*
> * With CFI clear in the Global Command register, we should be
> * protected from dangerous (i.e. compatibility) interrupts
> --
> 2.17.1
>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications
2020-08-26 5:29 ` Tian, Kevin
@ 2020-08-27 4:25 ` Lu Baolu
0 siblings, 0 replies; 3+ messages in thread
From: Lu Baolu @ 2020-08-27 4:25 UTC (permalink / raw)
To: Tian, Kevin, Joerg Roedel; +Cc: baolu.lu, iommu, Andy Lutomirski, linux-kernel
Hi Kevin,
On 8/26/20 1:29 PM, Tian, Kevin wrote:
>> From: Lu Baolu
>> Sent: Wednesday, August 26, 2020 10:58 AM
>>
>> The VT-d spec requires (10.4.4 Global Command Register, GCMD_REG
>> General
>> Description) that:
>>
>> If multiple control fields in this register need to be modified, software
>> must serialize the modifications through multiple writes to this register.
>>
>> However, in irq_remapping.c, modifications of IRE and CFI are done in one
>> write. We need to do two separate writes with STS checking after each.
>>
>> Fixes: af8d102f999a4 ("x86/intel/irq_remapping: Clean up x2apic opt-out
>> security warning mess")
>> Cc: Andy Lutomirski <luto@amacapital.net>
>> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> drivers/iommu/intel/irq_remapping.c | 8 ++++++--
>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/irq_remapping.c
>> b/drivers/iommu/intel/irq_remapping.c
>> index 9564d23d094f..19d7e18876fe 100644
>> --- a/drivers/iommu/intel/irq_remapping.c
>> +++ b/drivers/iommu/intel/irq_remapping.c
>> @@ -507,12 +507,16 @@ static void iommu_enable_irq_remapping(struct
>> intel_iommu *iommu)
>>
>> /* Enable interrupt-remapping */
>> iommu->gcmd |= DMA_GCMD_IRE;
>> - iommu->gcmd &= ~DMA_GCMD_CFI; /* Block compatibility-format
>> MSIs */
>> writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
>> -
>> IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
>> readl, (sts & DMA_GSTS_IRES), sts);
>>
>> + /* Block compatibility-format MSIs */
>> + iommu->gcmd &= ~DMA_GCMD_CFI;
>> + writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
>> + IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
>> + readl, !(sts & DMA_GSTS_CFIS), sts);
>> +
>
> Better do it only when CFI is actually enabled (by checking sts).
Yes. Make sense. Will send a new version with this changed.
Best regards,
baolu
>
>> /*
>> * With CFI clear in the Global Command register, we should be
>> * protected from dangerous (i.e. compatibility) interrupts
>> --
>> 2.17.1
>>
>> _______________________________________________
>> iommu mailing list
>> iommu@lists.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-08-27 4:31 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-08-26 2:58 [PATCH 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications Lu Baolu
2020-08-26 5:29 ` Tian, Kevin
2020-08-27 4:25 ` Lu Baolu
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).