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From: Oliver Upton <oliver.upton@linux.dev>
To: Ben Gardon <bgardon@google.com>
Cc: Ricardo Koller <ricarkol@google.com>, pbonzini@redhat.com,
	maz@kernel.org, yuzenghui@huawei.com, dmatlack@google.com,
	kvm@vger.kernel.org, kvmarm@lists.linux.dev, qperret@google.com,
	catalin.marinas@arm.com, andrew.jones@linux.dev, seanjc@google.com,
	alexandru.elisei@arm.com, suzuki.poulose@arm.com,
	eric.auger@redhat.com, gshan@redhat.com, reijiw@google.com,
	rananta@google.com, ricarkol@gmail.com
Subject: Re: [PATCH 1/9] KVM: arm64: Add KVM_PGTABLE_WALK_REMOVED into
 ctx->flags
Message-ID: <Y88sq1cQUzVj9B4D@google.com>
References: <20230113035000.480021-1-ricarkol@google.com>
 <20230113035000.480021-2-ricarkol@google.com>
 <CANgfPd9gMoR=F3uKhDtjsUV0efuoNvCLV0o0WoJKm9zx_PaKsQ@mail.gmail.com>
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On Mon, Jan 23, 2023 at 04:51:16PM -0800, Ben Gardon wrote:
> On Thu, Jan 12, 2023 at 7:50 PM Ricardo Koller <ricarkol@google.com> wrote:
> >
> > Add a flag to kvm_pgtable_visit_ctx, KVM_PGTABLE_WALK_REMOVED, to
> > indicate that the walk is on a removed table not accesible to the HW
> > page-table walker. Then use it to avoid doing break-before-make or
> > performing CMOs (Cache Maintenance Operations) when mapping a removed
> 
> Nit: Should this say unmapping? Or are we actually going to use this
> to map memory ?

I think the *_REMOVED term feels weird as it relates to constructing a
page table. It'd be better if we instead added flags to describe the
operations we intend to elide (i.e. CMOs and TLBIs). That way the
implementation is generic enough that we can repurpose it for other use
cases.

--
Thanks,
Oliver