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Re: [PATCH] x86/EPT: squash meaningless TLB flush
- To: Andrew Cooper <amc96@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 30 Nov 2021 17:57:37 +0100
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- Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 30 Nov 2021 16:57:52 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 30.11.2021 17:44, Andrew Cooper wrote:
> On 30/11/2021 16:10, 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>
>
> ept_free_entry() is called either recursively, or after an
> ept_split_super_page(), and I agree that it does not want to queue
> multiple flushes.
>
> However, I don't see where a suitable flush is in the superpage path.
> Am I overlooking something?
When it gets called after ept_split_super_page(), that's in case the
function failed (and hence no update to live page tables was made).
Jan
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