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Date:   Mon, 25 Jul 2022 14:05:59 +0700
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Subject: Re: [PATCH] iommu/amd: Disable guest vapic logging during early kdump
 init
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To:     Joerg Roedel <joro@8bytes.org>,
        Jerry Snitselaar <jsnitsel@redhat.com>
Cc:     Will Deacon <will@kernel.org>, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org
References: <20220721003439.403435-1-jsnitsel@redhat.com>
 <Ytq2GRX7UJjvXk4w@8bytes.org>
From:   Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
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Joeg / Jerry,

On 7/22/22 9:37 PM, Joerg Roedel wrote:
> 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.

Sorry for late reply. I have been actually working on the new GAM and GALOG enabling code,
which should also address this issue as well. I'll send out the patch soon.

Regards,
Suravee