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Message-ID: <97d106d28e4c3468912a478dba79ab2221109cbd.camel@redhat.com>
Date: Tue, 17 Oct 2023 17:51:59 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Cc: joro@...tes.org, seanjc@...gle.com, vasant.hegde@....com,
jon.grimm@....com, santosh.shukla@....com,
joao.m.martins@...cle.com, alejandro.j.jimenez@...cle.com,
boris.ostrovsky@...cle.com
Subject: Re: [PATCH] iommu/amd: Do not flush IRTE when only updating isRun
and destination fields
У вт, 2023-10-17 у 09:42 -0500, Suravee Suthikulpanit пише:
> According to the recent update in the AMD IOMMU spec [1], the IsRun and
> Destination fields of the Interrupt Remapping Table Entry (IRTE) are not
> cached by the IOMMU hardware.
Is that true for all AMD hardware that supports AVIC? E.g Zen1/Zen2 hardware?
Is there a chance that this will cause a similar errata to the is_running
errata that Zen2 cpus have?
>
> Therefore, do not issue the INVALIDATE_INTERRUPT_TABLE command when
> updating IRTE[IsRun] and IRTE[Destination] when IRTE[GuestMode]=1, which
> should help improve IOMMU AVIC/x2AVIC performance.
>
> References:
> [1] AMD IOMMU Spec Revision (Rev 3.08-PUB)
> (Link: https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/specifications/48882_IOMMU.pdf)
Looks like the link is broken.
Best regards,
Maxim Levitsky
>
> Cc: Joao Martins <joao.m.martins@...cle.com>
> Cc: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
> drivers/iommu/amd/iommu.c | 20 ++++++++++++++++----
> 1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 089886485895..d63590563d3e 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -2970,8 +2970,8 @@ static int alloc_irq_index(struct amd_iommu *iommu, u16 devid, int count,
> return index;
> }
>
> -static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
> - struct irte_ga *irte)
> +static int __modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
> + struct irte_ga *irte)
> {
> struct irq_remap_table *table;
> struct irte_ga *entry;
> @@ -2998,6 +2998,18 @@ static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
>
> raw_spin_unlock_irqrestore(&table->lock, flags);
>
> + return 0;
> +}
> +
> +static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
> + struct irte_ga *irte)
> +{
> + bool ret;
> +
> + ret = __modify_irte_ga(iommu, devid, index, irte);
> + if (ret)
> + return ret;
> +
> iommu_flush_irt_and_complete(iommu, devid);
>
> return 0;
> @@ -3681,8 +3693,8 @@ int amd_iommu_update_ga(int cpu, bool is_run, void *data)
> }
> entry->lo.fields_vapic.is_run = is_run;
>
> - return modify_irte_ga(ir_data->iommu, ir_data->irq_2_irte.devid,
> - ir_data->irq_2_irte.index, entry);
> + return __modify_irte_ga(ir_data->iommu, ir_data->irq_2_irte.devid,
> + ir_data->irq_2_irte.index, entry);
> }
> EXPORT_SYMBOL(amd_iommu_update_ga);
> #endif
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