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Date:   Fri, 22 Jul 2022 16:37:13 +0200
From:   Joerg Roedel <joro@8bytes.org>
To:     Jerry Snitselaar <jsnitsel@redhat.com>
Cc:     Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Will Deacon <will@kernel.org>, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/amd: Disable guest vapic logging during early
 kdump init
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References: <20220721003439.403435-1-jsnitsel@redhat.com>
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On Wed, Jul 20, 2022 at 05:34:39PM -0700, Jerry Snitselaar wrote:
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index 1d08f87e734b..2b00d7f28df7 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -815,6 +815,11 @@ static void free_ga_log(struct amd_iommu *iommu)
>  #endif
>  }
>  
> +static void iommu_ga_log_disable(struct amd_iommu *iommu)
> +{
> +	iommu_feature_disable(iommu, CONTROL_GALOG_EN);
> +}
> +
>  static int iommu_ga_log_enable(struct amd_iommu *iommu)
>  {
>  #ifdef CONFIG_IRQ_REMAP
> @@ -2504,6 +2509,7 @@ static void early_enable_iommus(void)
>  		for_each_iommu(iommu) {
>  			iommu_disable_command_buffer(iommu);
>  			iommu_disable_event_buffer(iommu);
> +			iommu_ga_log_disable(iommu);
>  			iommu_enable_command_buffer(iommu);
>  			iommu_enable_event_buffer(iommu);
>  			iommu_enable_ga(iommu);

Looks about right, but I also let Suravee comment on this.

Disabling the GA-Log under a device still using it should hopefully not
put it into some undefined state.