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Re: [PATCH v2 1/2] x86/spec: fix reporting of BHB clearing usage from guest entry points
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Thu, 25 Apr 2024 14:08:39 +0100
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- Cc: Jan Beulich <jbeulich@xxxxxxxx>
- Delivery-date: Thu, 25 Apr 2024 13:09:06 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18/04/2024 4:52 pm, Roger Pau Monne wrote:
> Reporting whether the BHB clearing on entry is done for the different domains
> types based on cpu_has_bhb_seq is incorrect, as that variable signals whether
I'd prefer s/incorrect/unhelpful/ here.
As pointed out, it's currently like IBPB-entry in this regard,
identifying whether the block is in place; not whether it's used by the
condition.
> there's a BHB clearing sequence selected, but that alone doesn't imply that
> such sequence is used from the PV and/or HVM entry points.
>
> Instead use opt_bhb_entry_{pv,hvm} which do signal whether BHB clearing is
> performed on entry from PV/HVM.
I was going to ask for a note about dom0, but instead I need to make a
correction to the cmdline docs. I'll do that in a separate patch.
> Fixes: 689ad48ce9cf ('x86/spec-ctrl: Wire up the Native-BHI software
> sequences')
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Can make the one tweak on commit.
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