linux-kernel - Re: [PATCH] iommu/amd: fix interrupt remapping for avic

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Date:   Mon, 14 Sep 2020 21:48:46 +0700
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, linux-kernel@...r.kernel.org
Cc:     "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        Joao Martins <joao.m.martins@...cle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] iommu/amd: fix interrupt remapping for avic

Maxim,

On 9/13/2020 7:42 PM, Maxim Levitsky wrote:
> Commit e52d58d54a32 ("iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE")
> accidentally removed an assumption that modify_irte_ga always set the valid bit
> and amd_iommu_activate_guest_mode relied on that.
> 
> Side effect of this is that on my machine, VFIO based VMs with AVIC enabled
> would eventually crash and show IOMMU errors like that:
> 
> AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0055 address=0xfffffffdf8000000 flags=0x0008]
> 
> Fixes: e52d58d54a321 ("iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE")
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>   drivers/iommu/amd/iommu.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 07ae8b93887e5..aff4cc1869356 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -3853,6 +3853,7 @@ int amd_iommu_activate_guest_mode(void *data)
>   	entry->hi.fields.ga_root_ptr       = ir_data->ga_root_ptr;
>   	entry->hi.fields.vector            = ir_data->ga_vector;
>   	entry->lo.fields_vapic.ga_tag      = ir_data->ga_tag;
> +	entry->lo.fields_remap.valid = 1;
>   
>   	return modify_irte_ga(ir_data->irq_2_irte.devid,
>   			      ir_data->irq_2_irte.index, entry, ir_data);
> 

Could you please try with the following patch instead?

--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3840,14 +3840,18 @@ 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;
@@ -3864,12 +3868,14 @@ int amd_iommu_deactivate_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;
         struct irq_cfg *cfg = ir_data->cfg;
-       u64 valid = entry->lo.fields_remap.valid;
+       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_remap.valid;
+
         entry->lo.val = 0;
         entry->hi.val = 0;
--

Thanks,
Suravee