From: Quentin Perret <qperret@google.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kernel-team@android.com, qwandor@google.com, will@kernel.org,
catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 09/14] KVM: arm64: Mark host bss and rodata section as shared
Date: Mon, 19 Jul 2021 16:56:57 +0100 [thread overview]
Message-ID: <YPWgyS7i2sMtiX8S@google.com> (raw)
In-Reply-To: <87eebujqjv.wl-maz@kernel.org>
On Monday 19 Jul 2021 at 16:01:40 (+0100), Marc Zyngier wrote:
> On Mon, 19 Jul 2021 11:47:30 +0100,
> Quentin Perret <qperret@google.com> wrote:
> > +static int finalize_mappings(void)
> > +{
> > + enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_RWX;
> > + int ret;
> > +
> > + /*
> > + * The host's .bss and .rodata sections are now conceptually owned by
> > + * the hypervisor, so mark them as 'borrowed' in the host stage-2. We
> > + * can safely use host_stage2_idmap_locked() at this point since the
> > + * host stage-2 has not been enabled yet.
> > + */
> > + prot |= KVM_PGTABLE_STATE_SHARED | KVM_PGTABLE_STATE_BORROWED;
> > + ret = host_stage2_idmap_locked(__hyp_pa(__start_rodata),
> > + __hyp_pa(__end_rodata), prot);
>
> Do we really want to map the rodata section as RWX?
I know, feels odd, but for now I think so. The host is obviously
welcome to restrict things in its stage-1, but for stage-2, this is
just 'memory' so far, the host is allowed to patch it if it wants too.
Eventually, yes, I think we should make it RO in the host stage-2, but
maybe that's for another series?
> > + if (ret)
> > + return ret;
> > +
> > + return host_stage2_idmap_locked(__hyp_pa(__hyp_bss_end),
> > + __hyp_pa(__bss_stop), prot);
>
> If the 'locked' state implies SHARED+BORROWED, maybe consider moving
> the ORRing of the prot into host_stage2_idmap_locked()?
Ah no, sorry for the confusion, but 'locked' means that we already hold
the pgtable lock. That is not actually true here, but this is a special
case as only the current CPU can be messing with it at this point in
time so taking the lock would just be wasted cycles.
> > +}
> > +
> > void __noreturn __pkvm_init_finalise(void)
> > {
> > struct kvm_host_data *host_data = this_cpu_ptr(&kvm_host_data);
> > @@ -167,6 +199,10 @@ void __noreturn __pkvm_init_finalise(void)
> > if (ret)
> > goto out;
> >
> > + ret = finalize_mappings();
> > + if (ret)
> > + goto out;
> > +
> > pkvm_pgtable_mm_ops = (struct kvm_pgtable_mm_ops) {
> > .zalloc_page = hyp_zalloc_hyp_page,
> > .phys_to_virt = hyp_phys_to_virt,
Thanks,
Quentin
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next prev parent reply other threads:[~2021-07-19 15:57 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 10:47 [PATCH 00/14] Track shared pages at EL2 in protected mode Quentin Perret
2021-07-19 10:47 ` [PATCH 01/14] KVM: arm64: Provide the host_stage2_try() helper macro Quentin Perret
2021-07-20 13:57 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 02/14] KVM: arm64: Optimize kvm_pgtable_stage2_find_range() Quentin Perret
2021-07-19 10:47 ` [PATCH 03/14] KVM: arm64: Continue stage-2 map when re-creating mappings Quentin Perret
2021-07-19 12:14 ` Marc Zyngier
2021-07-19 13:32 ` Quentin Perret
2021-07-20 8:26 ` Marc Zyngier
2021-07-20 11:56 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 04/14] KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED Quentin Perret
2021-07-19 10:47 ` [PATCH 05/14] KVM: arm64: Don't overwrite ignored bits with owner id Quentin Perret
2021-07-19 12:55 ` Marc Zyngier
2021-07-19 13:39 ` Quentin Perret
2021-07-20 8:46 ` Marc Zyngier
2021-07-19 10:47 ` [PATCH 06/14] KVM: arm64: Tolerate re-creating hyp mappings to set ignored bits Quentin Perret
2021-07-20 10:17 ` Fuad Tabba
2021-07-20 10:30 ` Quentin Perret
2021-07-20 10:59 ` Fuad Tabba
2021-07-20 11:14 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 07/14] KVM: arm64: Enable forcing page-level stage-2 mappings Quentin Perret
2021-07-19 14:24 ` Marc Zyngier
2021-07-19 15:36 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 08/14] KVM: arm64: Add support for tagging shared pages in page-table Quentin Perret
2021-07-19 14:43 ` Marc Zyngier
2021-07-19 15:49 ` Quentin Perret
2021-07-20 10:13 ` Marc Zyngier
2021-07-20 11:48 ` Quentin Perret
2021-07-20 13:48 ` Fuad Tabba
2021-07-20 14:06 ` Quentin Perret
2021-07-21 7:34 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 09/14] KVM: arm64: Mark host bss and rodata section as shared Quentin Perret
2021-07-19 15:01 ` Marc Zyngier
2021-07-19 15:56 ` Quentin Perret [this message]
2021-07-19 10:47 ` [PATCH 10/14] KVM: arm64: Enable retrieving protections attributes of PTEs Quentin Perret
2021-07-19 10:47 ` [PATCH 11/14] KVM: arm64: Expose kvm_pte_valid() helper Quentin Perret
2021-07-21 8:20 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 12/14] KVM: arm64: Refactor pkvm_pgtable locking Quentin Perret
2021-07-21 8:37 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 13/14] KVM: arm64: Restrict hyp stage-1 manipulation in protected mode Quentin Perret
2021-07-21 10:45 ` Fuad Tabba
2021-07-21 13:35 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 14/14] KVM: arm64: Prevent late calls to __pkvm_create_private_mapping() Quentin Perret
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