From: "Ard Biesheuvel" <ardb@kernel.org>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Michael Brown <mcb30@ipxe.org>,
devel@edk2.groups.io, Jiewen Yao <jiewen.yao@intel.com>,
Jordan Justen <jordan.l.justen@intel.com>
Subject: Re: [edk2-devel] [PATCH 1/1] OvmfPkg/IoMmuDxe: add locking to IoMmuAllocateBounceBuffer
Date: Thu, 20 Jul 2023 14:45:43 +0200 [thread overview]
Message-ID: <CAMj1kXFDdLxoZ-53qnNRVOP62H3-t+rfPiopAJ256GSVd8AXKw@mail.gmail.com> (raw)
In-Reply-To: <57y2vtkzqkqjfoft2vn7gem527frwh3i4ymk7piaztyxlfz4fz@eqeuogfkl5vf>
On Thu, 20 Jul 2023 at 10:28, Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> > > > mReservedMemBitmap &= (UINT32)(~MapInfo->ReservedMemBitmap);
> > >
> > > I'd expect modern compilers optimize that to a single instruction,
> >
> > You mean something along the lines of
> >
> > andl %reg, mReservedMemBitmap(%rip)
> >
> > right?
>
> Yes.
>
> > > but
> > > yes, it's not guaranteed to happen, the compiler can choose to generate
> > > a series of load + and + store instructions instead.
> >
> > That is sadly all we have on ARM, unless you use LSE atomics, which
> > are optional in the architecture so we never use those in EDK2.
>
> ARM means v7 only or both v7+v8?
>
All of it.
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prev parent reply other threads:[~2023-07-20 12:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-19 11:33 [edk2-devel] [PATCH 1/1] OvmfPkg/IoMmuDxe: add locking to IoMmuAllocateBounceBuffer Gerd Hoffmann
2023-07-19 16:04 ` Michael Brown
2023-07-19 16:31 ` Gerd Hoffmann
2023-07-19 16:52 ` Ard Biesheuvel
2023-07-19 17:40 ` Michael Brown
2023-07-19 22:06 ` Ard Biesheuvel
2023-07-20 8:30 ` Gerd Hoffmann
2023-07-20 8:28 ` Gerd Hoffmann
2023-07-20 12:45 ` Ard Biesheuvel [this message]
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