netdev - Re: [EXTERNAL] [PATCH] vhost: fix caching attributes of MMIO regions by setting them explicitly

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Message-ID: <ECE065A9-1556-4525-A478-62343C6FB477@marvell.com>
Date: Tue, 13 Jan 2026 06:19:51 +0000
From: Shiva Shankar Kommula <kshankar@...vell.com>
To: "mst@...hat.com" <mst@...hat.com>
CC: "jasowang@...hat.com" <jasowang@...hat.com>,
        "virtualization@...ts.linux.dev" <virtualization@...ts.linux.dev>,
        "eperezma@...hat.com" <eperezma@...hat.com>,
        "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jerin Jacob <jerinj@...vell.com>,
        Nithin Kumar Dabilpuram
	<ndabilpuram@...vell.com>,
        Srujana Challa <schalla@...vell.com>
Subject: Re: [EXTERNAL] [PATCH] vhost: fix caching attributes of MMIO regions
 by setting them explicitly

Hi Michael, 
Just a ping on this patch. Would appreciate your review when you get a chance.

Thanks


> On 2 Jan 2026, at 12:27, Kommula Shiva Shankar <kshankar@...vell.com> wrote:
> 
> Prioritize security for external emails:
> Confirm sender and content safety before clicking links or opening attachments
> Report Suspicious
> Explicitly set non-cached caching attributes for MMIO regions.
> Default write-back mode can cause CPU to cache device memory,
> causing invalid reads and unpredictable behavior.
> 
> Invalid read and write issues were observed on ARM64 when mapping the
> notification area to userspace via mmap.
> 
> Signed-off-by: Kommula Shiva Shankar <kshankar@...vell.com>
> Acked-by: Jason Wang <jasowang@...hat.com>
> ---
> Originally sent to net-next, now redirected to vhost tree
> per Jason Wang's suggestion. 
> 
> drivers/vhost/vdpa.c | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 05a481e4c385..b0179e8567ab 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -1527,6 +1527,7 @@ static int vhost_vdpa_mmap(struct file *file, struct vm_area_struct *vma)
> if (vma->vm_end - vma->vm_start != notify.size)
> return -ENOTSUPP;
> 
> + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
> vma->vm_ops = &vhost_vdpa_vm_ops;
> return 0;
> -- 
> 2.48.1
> 
> 
> 
>