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Re: [PATCH] x86/shadow: depend on PV || HVM
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 16 Apr 2021 13:39:46 +0100
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On 16/04/2021 13:32, Jan Beulich wrote:
> With the building of guest_?.o now depending on PV or HVM, without
> further #ifdef-ary shadow code won't link anymore when !PV && !HVM.
> Since this isn't a useful configuration anyway, exclude shadow code from
> being built in this case.
>
> Fixes: aff8bf94ce65 ("x86/shadow: only 4-level guest code needs building when
> !HVM")
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -121,6 +121,7 @@ config XEN_SHSTK
> config SHADOW_PAGING
> bool "Shadow Paging"
> default !PV_SHIM_EXCLUSIVE
Hang on - this is bug, and is what needs dropping.
PV Shim uses Shadow, in default configurations, for L1TF protections to
keep userspace out of the guest kernel. Without it, the shim'd guest
will be crashed when it writes an L1TF-vulnerable PTE.
OSSTest ought to have blocked this as a regression, but I suspect its
not running the XTF PV guests in shim mode.
~Andrew
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