Re: [PATCH] xen/arm: call uaccess_ttbr0_enable for dm_op hypercall

["Jürgen Groß" <jgross@suse.com>]

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On 12.05.25 23:54, Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabellini@amd.com>
> 
> dm_op hypercalls might come from userspace and pass memory addresses as
> parameters. The memory addresses typically correspond to buffers
> allocated in userspace to hold extra hypercall parameters.
> 
> On ARM, when CONFIG_ARM64_SW_TTBR0_PAN is enabled, they might not be
> accessible by Xen, as a result ioreq hypercalls might fail. See the
> existing comment in arch/arm64/xen/hypercall.S regarding privcmd_call
> for reference.
> 
> For privcmd_call, Linux calls uaccess_ttbr0_enable before issuing the
> hypercall thanks to commit 9cf09d68b89a. We need to do the same for
> dm_op. This resolves the problem.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
> Fixes: 9cf09d68b89a ("arm64: xen: Enable user access before a privcmd
> hvc call")
> Cc: stable@kernel.org

I'm not an Arm specialist, but looking at the surrounding code this
seems to be correct.

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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