linux-kernel - Re: [PATCH] vfio/type1: Initialize resv_msi

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Date:   Tue, 15 Oct 2019 17:49:29 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     Cornelia Huck <cohuck@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH] vfio/type1: Initialize resv_msi_base

Hi Joerg,

On 10/15/19 5:16 PM, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> After enabling CONFIG_IOMMU_DMA on X86 a new warning appears when
> compiling vfio:
> 
> drivers/vfio/vfio_iommu_type1.c: In function ‘vfio_iommu_type1_attach_group’:
> drivers/vfio/vfio_iommu_type1.c:1827:7: warning: ‘resv_msi_base’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>    ret = iommu_get_msi_cookie(domain->domain, resv_msi_base);
>    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> The warning is a false positive, because the call to iommu_get_msi_cookie()
> only happens when vfio_iommu_has_sw_msi() returned true. And that only
> happens when it also set resv_msi_base.
> 
> But initialize the variable anyway to get rid of the warning.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 96fddc1dafc3..d864277ea16f 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1658,7 +1658,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	struct bus_type *bus = NULL;
>  	int ret;
>  	bool resv_msi, msi_remap;
> -	phys_addr_t resv_msi_base;
> +	phys_addr_t resv_msi_base = 0;
>  	struct iommu_domain_geometry geo;
>  	LIST_HEAD(iova_copy);
>  	LIST_HEAD(group_resv_regions);
> 
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric