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Message-ID: <b12b9b4b-4a2a-4499-8c71-73b8d2338dec@oracle.com>
Date: Thu, 28 Sep 2023 18:27:57 +0100
From: Joao Martins <joao.m.martins@...cle.com>
To: Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc: Will Deacon <will@...nel.org>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Paolo Bonzini <pbonzini@...hat.com>, x86@...nel.org,
Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
Ingo Molnar <mingo@...hat.com>, Joerg Roedel <joro@...tes.org>,
Sean Christopherson <seanjc@...gle.com>,
"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] iommu/amd: skip updating the IRTE entry when is_run
is already false
On 28/09/2023 16:04, Maxim Levitsky wrote:
> When vCPU affinity of an IRTE which already has
> is_run == false, is updated and the update also sets is_run to false,
> there is nothing to do.
>
> The goal of this patch is to make a call to 'amd_iommu_update_ga()'
> to be relatively cheap if there is nothing to do.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
Reviewed-by: Joao Martins <joao.m.martins@...cle.com>
> ---
> drivers/iommu/amd/iommu.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 95bd7c25ba6f366..10bcd436e984672 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -3774,6 +3774,15 @@ int amd_iommu_update_ga(int cpu, bool is_run, void *data)
> entry->hi.fields.destination =
> APICID_TO_IRTE_DEST_HI(cpu);
> }
> +
> + if (!is_run && !entry->lo.fields_vapic.is_run) {
> + /*
> + * No need to notify the IOMMU about an entry which
> + * already has is_run == False
> + */
> + return 0;
> + }
> +
> entry->lo.fields_vapic.is_run = is_run;
>
> return modify_irte_ga(ir_data->iommu, ir_data->irq_2_irte.devid,
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