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Re: [PATCH v3 04/12] x86/shadow: use lighter weight mode checks
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 20 Feb 2026 14:55:55 +0000
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>
- Delivery-date: Fri, 20 Feb 2026 14:56:09 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16/05/2023 8:39 am, Jan Beulich wrote:
> shadow_mode_...(), with the exception of shadow_mode_enabled(), are
> shorthands for shadow_mode_enabled() && paging_mode_...(). While
> potentially useful outside of shadow-internal functions, when we already
> know that we're dealing with a domain in shadow mode, the "paging"
> checks are sufficient and cheaper. While the "shadow" ones commonly
> translate to a MOV/AND/CMP/Jcc sequence, the "paging" ones typically
> resolve to just TEST+Jcc.
That's because shadow_*() are checking a minimum of 2 bits, while most
of the paging_*() ones are only checking a single bit.
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
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