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| Started by | Feng Wu <feng.wu@intel.com> |
|---|---|
| First post | 2015-10-15 04:40 +0200 |
| Last post | 2015-10-16 03:10 +0200 |
| Articles | 3 — 3 participants |
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[PATCH] iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically Feng Wu <feng.wu@intel.com> - 2015-10-15 04:40 +0200
Re: [PATCH] iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically Joerg Roedel <joro@8bytes.org> - 2015-10-15 16:30 +0200
RE: [PATCH] iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically "Wu, Feng" <feng.wu@intel.com> - 2015-10-16 03:10 +0200
| From | Feng Wu <feng.wu@intel.com> |
|---|---|
| Date | 2015-10-15 04:40 +0200 |
| Subject | [PATCH] iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically |
| Message-ID | <qjGCt-1cI-3@gated-at.bofh.it> |
If IRTE is in posted format, the 'pda' field goes across the 64-bit
boundary, we need use cmpxchg16b to atomically update it. We only
expose posted-interrupt when X86_FEATURE_CX16 is supported and use
to update it atomically.
Signed-off-by: Feng Wu <feng.wu@intel.com>
---
drivers/iommu/intel_irq_remapping.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index f15692a..b4f7569 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -169,8 +169,26 @@ static int modify_irte(struct irq_2_iommu *irq_iommu,
index = irq_iommu->irte_index + irq_iommu->sub_handle;
irte = &iommu->ir_table->base[index];
- set_64bit(&irte->low, irte_modified->low);
- set_64bit(&irte->high, irte_modified->high);
+#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE)
+ if ((irte->pst == 1) || (irte_modified->pst == 1)) {
+ bool ret;
+
+ ret = cmpxchg_double(&irte->low, &irte->high,
+ irte->low, irte->high,
+ irte_modified->low, irte_modified->high);
+ /*
+ * We use cmpxchg16 to atomically update the 128-bit IRTE,
+ * and it cannot be updated by the hardware or other processors
+ * behind us, so the return value of cmpxchg16 should be the
+ * same as the old value.
+ */
+ BUG_ON(!ret);
+ } else
+#endif
+ {
+ set_64bit(&irte->low, irte_modified->low);
+ set_64bit(&irte->high, irte_modified->high);
+ }
__iommu_flush_cache(iommu, irte, sizeof(*irte));
rc = qi_flush_iec(iommu, index, 0);
@@ -725,7 +743,16 @@ static inline void set_irq_posting_cap(void)
struct intel_iommu *iommu;
if (!disable_irq_post) {
- intel_irq_remap_ops.capability |= 1 << IRQ_POSTING_CAP;
+ /*
+ * If IRTE is in posted format, the 'pda' field goes across the
+ * 64-bit boundary, we need use cmpxchg16b to atomically update
+ * it. We only expose posted-interrupt when X86_FEATURE_CX16
+ * is supported. Actually, hardware platforms supporting PI
+ * should have X86_FEATURE_CX16 support, this has been confirmed
+ * with Intel hardware guys.
+ */
+ if ( cpu_has_cx16 )
+ intel_irq_remap_ops.capability |= 1 << IRQ_POSTING_CAP;
for_each_iommu(iommu, drhd)
if (!cap_pi_support(iommu->cap)) {
--
2.1.0
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| From | Joerg Roedel <joro@8bytes.org> |
|---|---|
| Date | 2015-10-15 16:30 +0200 |
| Subject | Re: [PATCH] iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically |
| Message-ID | <qjRHz-AM-1@gated-at.bofh.it> |
| In reply to | #1247349 |
On Thu, Oct 15, 2015 at 10:19:11AM +0800, Feng Wu wrote:
> If IRTE is in posted format, the 'pda' field goes across the 64-bit
> boundary, we need use cmpxchg16b to atomically update it. We only
> expose posted-interrupt when X86_FEATURE_CX16 is supported and use
> to update it atomically.
>
> Signed-off-by: Feng Wu <feng.wu@intel.com>
> ---
> drivers/iommu/intel_irq_remapping.c | 33 ++++++++++++++++++++++++++++++---
> 1 file changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
> index f15692a..b4f7569 100644
> --- a/drivers/iommu/intel_irq_remapping.c
> +++ b/drivers/iommu/intel_irq_remapping.c
> @@ -169,8 +169,26 @@ static int modify_irte(struct irq_2_iommu *irq_iommu,
> index = irq_iommu->irte_index + irq_iommu->sub_handle;
> irte = &iommu->ir_table->base[index];
>
> - set_64bit(&irte->low, irte_modified->low);
> - set_64bit(&irte->high, irte_modified->high);
> +#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE)
> + if ((irte->pst == 1) || (irte_modified->pst == 1)) {
> + bool ret;
> +
> + ret = cmpxchg_double(&irte->low, &irte->high,
> + irte->low, irte->high,
> + irte_modified->low, irte_modified->high);
> + /*
> + * We use cmpxchg16 to atomically update the 128-bit IRTE,
> + * and it cannot be updated by the hardware or other processors
> + * behind us, so the return value of cmpxchg16 should be the
> + * same as the old value.
> + */
> + BUG_ON(!ret);
Changed this to a WARN_ON, otherwise applied.
--
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| From | "Wu, Feng" <feng.wu@intel.com> |
|---|---|
| Date | 2015-10-16 03:10 +0200 |
| Subject | RE: [PATCH] iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically |
| Message-ID | <qk1GW-7np-9@gated-at.bofh.it> |
| In reply to | #1247840 |
> -----Original Message----- > From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel- > owner@vger.kernel.org] On Behalf Of Joerg Roedel > Sent: Thursday, October 15, 2015 10:24 PM > To: Wu, Feng <feng.wu@intel.com> > Cc: iommu@lists.linux-foundation.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH] iommu/vt-d: Use cmpxchg16b to update posted format > IRTE atomically > > On Thu, Oct 15, 2015 at 10:19:11AM +0800, Feng Wu wrote: > > If IRTE is in posted format, the 'pda' field goes across the 64-bit > > boundary, we need use cmpxchg16b to atomically update it. We only > > expose posted-interrupt when X86_FEATURE_CX16 is supported and use > > to update it atomically. > > + > > + ret = cmpxchg_double(&irte->low, &irte->high, > > + irte->low, irte->high, > > + irte_modified->low, irte_modified->high); > > + /* > > + * We use cmpxchg16 to atomically update the 128-bit IRTE, > > + * and it cannot be updated by the hardware or other > processors > > + * behind us, so the return value of cmpxchg16 should be the > > + * same as the old value. > > + */ > > + BUG_ON(!ret); > > Changed this to a WARN_ON, otherwise applied. Thanks a lot, Joerg! Thanks, Feng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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