Re: [PATCH v2 6/6] x86/hvm: reduce the need to flush caches in memory_type_changed()

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, May 19, 2025 at 03:22:32PM +0200, Jan Beulich wrote:
> On 19.05.2025 13:08, Roger Pau Monné wrote:
> > On Sun, May 18, 2025 at 01:44:49PM +0200, Jan Beulich wrote:
> >> On 16.05.2025 11:45, Roger Pau Monne wrote:
> >>> Not sure whether this attempt to reduce cache flushing should get some
> >>> mention in the CHANGELOG.
> >>
> >> Err on the side of adding an entry there?
> > 
> > Oleksii would you be fine with me adding:
> > 
> > diff --git a/CHANGELOG.md b/CHANGELOG.md
> > index 1ea06524db20..fa971cd9e6ee 100644
> > --- a/CHANGELOG.md
> > +++ b/CHANGELOG.md
> > @@ -11,6 +11,9 @@ The format is based on [Keep a 
> > Changelog](https://keepachangelog.com/en/1.0.0/)
> >     - For x86, GCC 5.1 and Binutils 2.25, or Clang/LLVM 11
> >     - For ARM32 and ARM64, GCC 5.1 and Binutils 2.25
> >   - Linux based device model stubdomains are now fully supported.
> > + - On x86:
> > +   - Restrict the cache flushing done in memory_type_changed() to improve
> > +     performance.
> 
> Maybe better to mention function names here, saying "after a memory type 
> change
> by a guest" instead?

It's not just "after a memory type change by a guest", since
memory_type_changed() is also used for toolstack operations like
io{mem,ports}_{permit,deny}_access(), that strictly speaking are not
memory type changes, neither are done by the guest itself.  I could
reword to:

   - Restrict the cache flushing done as a result of guest physical
     memory map manipulations and memory type changes.

Does that sound better?

Thanks, Roger.