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Re: [PATCH] x86/EPT: squash meaningless TLB flush
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Fri, 10 Dec 2021 11:30:09 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "Jun Nakajima" <jun.nakajima@xxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>
- Delivery-date: Fri, 10 Dec 2021 10:30:35 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Tue, Nov 30, 2021 at 05:10:53PM +0100, Jan Beulich wrote:
> ept_free_entry() gets called after a flush - if one is necessary in the
> first place - was already issued. That behavior is similar to NPT, which
> also doesn't have any further flush in p2m_free_entry(). (Furthermore,
> the function being recursive, in case of recursiveness way too many
> flushes would have been issued.)
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
It's also worth noting that ept_free_entry doesn't modify the p2m
itself - it gets handed an EPT entry to free, which should have been
unhooked from the p2m previously by the caller, so it should be the
responsibility of the caller to perform any flushes.
Thanks, Roger.
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