linux-kernel - Re: [PATCH] iommu/amd: Fix "Guest Virtual APIC Table Root Pointer" configuration in IRTE

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Date:   Mon, 3 Apr 2023 11:11:30 +0100
From:   Joao Martins <joao.m.martins@...cle.com>
To:     "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>,
        Kishon Vijay Abraham I <kvijayab@....com>
Cc:     Vasant Hegde <vasant.hegde@....com>,
        Santosh Shukla <santosh.shukla@....com>,
        "Nikunj A . Dadhania" <nikunj@....com>,
        Will Deacon <will@...nel.org>, iommu@...ts.linux.dev,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org, boris.ostrovsky@...cle.com,
        alejandro.j.jimenez@...cle.com, Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] iommu/amd: Fix "Guest Virtual APIC Table Root Pointer"
 configuration in IRTE

On 03/04/2023 05:29, Suthikulpanit, Suravee wrote:
> Kishon,
> 
> On 3/31/2023 1:17 PM, Kishon Vijay Abraham I wrote:
>> commit b9c6ff94e43a ("iommu/amd: Re-factor guest virtual APIC
>> (de-)activation code") while refactoring guest virtual APIC
>> activation/de-activation code, stored information for activate/de-activate
>> in "struct amd_ir_data". It used 32-bit integer data type for storing the
>> "Guest Virtual APIC Table Root Pointer" (ga_root_ptr), though the
>> "ga_root_ptr" is actually a 40-bit field in IRTE (Interrupt Remapping
>> Table Entry).
>>
>> This causes interrupts from PCIe devices to not reach the guest in the case
>> of PCIe passthrough with SME (Secure Memory Encryption) enabled as _SME_
>> bit in the "ga_root_ptr" is lost before writing it to the IRTE.
>>
>> Fix it by using 64-bit data type for storing the "ga_root_ptr".
>>
>> Fixes: b9c6ff94e43a ("iommu/amd: Re-factor guest virtual APIC (de-)activation
>> code")
>> Cc: stable@...r.kernel.org # v5.4+
>> Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
>> Signed-off-by: Kishon Vijay Abraham I <kvijayab@....com>
> 
> Please also add
> Reported-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
> ---
>  drivers/iommu/amd/amd_iommu_types.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
> index 3d684190b4d5..990614b8a1fe 100644
> --- a/drivers/iommu/amd/amd_iommu_types.h
> +++ b/drivers/iommu/amd/amd_iommu_types.h
> @@ -1001,7 +1001,7 @@ struct amd_ir_data {
>  	 */
>  	struct irq_cfg *cfg;
>  	int ga_vector;
> -	int ga_root_ptr;
> +	u64 ga_root_ptr;
>  	int ga_tag;
>  };

Nice catch. While at it I noticed the following:

* ga_tag: The conversion of uint (in kvm as they use proper u32 for gatag) to
int will miss a bit thus at least VM IDs with the msb set will be stripped from
vCPU wake ups? Fortunately the 24 bits for VCPU ID wouldn't be affected. But
ga_tag should probably be a u32.

* ga_vector: this in principle should be u8 per spec, maybe it is OK to stay as
is to prevent compiler warnings as IOMMU intremap struct vcpu_data is using a u32.

	Joao