linux-kernel - Re: [PATCH v2] iommu/amd: Restore IRTE.RemapEn bit for amd_iommu_activate_guest

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Message-ID: <3dd694a9-ad1e-f9ed-ac9b-20052f985f38@oracle.com>
Date:   Wed, 16 Sep 2020 18:10:08 +0100
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc:     mlevitsk@...hat.com, joro@...tes.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v2] iommu/amd: Restore IRTE.RemapEn bit for
 amd_iommu_activate_guest_mode

On 9/16/20 12:17 PM, Suravee Suthikulpanit wrote:
> Commit e52d58d54a32 ("iommu/amd: Use cmpxchg_double() when updating
> 128-bit IRTE") removed an assumption that modify_irte_ga always set
> the valid bit, which requires the callers to set the appropriate value
> for the struct irte_ga.valid bit before calling the function.
> 
> Similar to the commit 26e495f34107 ("iommu/amd: Restore IRTE.RemapEn
> bit after programming IRTE"), which is for the function
> amd_iommu_deactivate_guest_mode().
> 
> The same change is also needed for the amd_iommu_activate_guest_mode().
> Otherwise, this could trigger IO_PAGE_FAULT for the VFIO based VMs with
> AVIC enabled.
> 
> Reported-by: Maxim Levitsky <mlevitsk@...hat.com>
> Tested-by: Maxim Levitsky <mlevitsk@...hat.com>
> Cc: Joao Martins <joao.m.martins@...cle.com>
> Fixes: e52d58d54a321 ("iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE")
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  drivers/iommu/amd/iommu.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index e938677af8bc..db4fb840c59c 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -3900,14 +3900,18 @@ int amd_iommu_activate_guest_mode(void *data)
>  {
>  	struct amd_ir_data *ir_data = (struct amd_ir_data *)data;
>  	struct irte_ga *entry = (struct irte_ga *) ir_data->entry;
> +	u64 valid;
>  
>  	if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) ||
>  	    !entry || entry->lo.fields_vapic.guest_mode)
>  		return 0;
>  
> +	valid = entry->lo.fields_vapic.valid;
> +
>  	entry->lo.val = 0;
>  	entry->hi.val = 0;
>  
> +	entry->lo.fields_vapic.valid       = valid;
>  	entry->lo.fields_vapic.guest_mode  = 1;
>  	entry->lo.fields_vapic.ga_log_intr = 1;
>  	entry->hi.fields.ga_root_ptr       = ir_data->ga_root_ptr;
> 
FWIW,

Reviewed-by: Joao Martins <joao.m.martins@...cle.com>