From: Sebastian Ene <sebastianene@google.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: catalin.marinas@arm.com, gshan@redhat.com, james.morse@arm.com,
mark.rutland@arm.com, maz@kernel.org, rananta@google.com,
ricarkol@google.com, ryan.roberts@arm.com, shahuang@redhat.com,
suzuki.poulose@arm.com, will@kernel.org, yuzenghui@huawei.com,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kernel-team@android.com,
vdonnefort@google.com
Subject: Re: [PATCH v5 4/4] KVM: arm64: Initialize the ptdump parser with stage-2 attributes
Date: Wed, 14 Feb 2024 16:29:45 +0000 [thread overview]
Message-ID: <ZczqeTEOVVcRPNi3@google.com> (raw)
In-Reply-To: <ZcuihokcWA3q-pZS@linux.dev>
On Tue, Feb 13, 2024 at 05:10:30PM +0000, Oliver Upton wrote:
> On Tue, Feb 13, 2024 at 04:59:01PM +0000, Sebastian Ene wrote:
> > On Tue, Feb 13, 2024 at 12:42:42AM +0000, Oliver Upton wrote:
> > > On Wed, Feb 07, 2024 at 02:48:33PM +0000, Sebastian Ene wrote:
>
> [...]
>
> > > > +
> > > > + snprintf(marker_msg, MARKER_MSG_LEN, "IPA bits %2u start lvl %1d",
> > > > + pgtable->ia_bits, pgtable->start_level);
> > > > +
> > > > + ipa_addr_marker[0].name = marker_msg;
> > >
> > > Is the dynamic name worth the added complexity? I see nothing wrong with
> > > exposing additional debugfs files for simple attributes like the IPA
> > > range and page table levels.
> > >
> > > I know it isn't *that* much, just looking for every opportunity to
> > > simplify further.
> > >
> >
> > We can keep them separate, I have no strong opinion about this. I think
> > this was Vincent's, original suggestion to have them so I will check with
> > him as well.
>
> Well, if we get to the place where there's a single struct containing
> all of the required data upfront then this becomes less of an issue.
> This is useful information still, so let's see if we can go about it the
> other way.
>
Allright, I will create separate entries for getting the ipa_space and the start
level which will be exposed in the vm debugfs dir.
> > > > + ret = kvm_ptdump_parser_init(&parser_state, mmu->pgt, m);
> > > > + if (ret)
> > > > + return ret;
> > > > +
> > >
> > > Can this be done at open(), or am I missing something?
> > >
> >
> > I guess we can do this in open() but then we will have to add again that
> > struct that wraps some ptdump specific state tracking. It seemed a bit cleaner in
> > this way. What do you think ?
>
> Allocating something that looks like an iterator end embedding it in
> ->private isn't too uncommon.
>
Ack, will stick to this approach in this case.
> > > > write_lock(&guest_kvm->mmu_lock);
> > > > ret = kvm_ptdump_show_common(m, mmu->pgt, &parser_state);
> > > > write_unlock(&guest_kvm->mmu_lock);
> > > >
> > > > + kvm_ptdump_parser_teardown(&parser_state);
> > >
> > > Same question here, can this happen at close()? I guess you'll need a
> > > struct to encapsulate pg_state and a pointer to the VM at least.
> > >
> >
> > Right, I tried to avoid using a separate struct as we discussed in v4.
>
> Sorry, I hope I didn't confuse you in my prior feedback.
>
> What I had issue with was the multiple layers of function ptr / ops
> structs for managing the file interface. I have zero concerns with
> organizing the _data_ for the walk this way.
>
Right, I see what you mean, thanks for the clarification.
> > > Actually, come to think of it, if you embed all of the data you need for
> > > the walker into a structure you can just do a single allocation for it
> > > upfront.
>
> --
> Thanks,
> Oliver
Thanks for the feedback,
Seb
prev parent reply other threads:[~2024-02-14 16:29 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-07 14:48 [PATCH v5 0/4] arm64: ptdump: View the second stage page-tables Sebastian Ene
2024-02-07 14:48 ` [PATCH v5 1/4] arm64: ptdump: Expose the attribute parsing functionality Sebastian Ene
2024-02-07 14:48 ` [PATCH v5 2/4] arm64: ptdump: Use the mask from the state structure Sebastian Ene
2024-02-07 14:48 ` [PATCH v5 3/4] KVM: arm64: Register ptdump with debugfs on guest creation Sebastian Ene
2024-02-13 0:56 ` Oliver Upton
2024-02-13 16:42 ` Sebastian Ene
2024-02-13 16:51 ` Oliver Upton
2024-02-07 14:48 ` [PATCH v5 4/4] KVM: arm64: Initialize the ptdump parser with stage-2 attributes Sebastian Ene
2024-02-13 0:42 ` Oliver Upton
2024-02-13 16:59 ` Sebastian Ene
2024-02-13 17:10 ` Oliver Upton
2024-02-14 16:29 ` Sebastian Ene [this message]
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