On Tue, 20 Jul 2021 16:49:45 +0100,
Quentin Perret [off-list ref] wrote:

On Tuesday 20 Jul 2021 at 14:15:56 (+0100), Marc Zyngier wrote:

quoted

On Tue, 20 Jul 2021 12:13:20 +0100,
Quentin Perret [off-list ref] wrote:

quoted

On Thursday 15 Jul 2021 at 17:31:47 (+0100), Marc Zyngier wrote:

quoted

+struct s2_walk_data {
+	kvm_pte_t	pteval;
+	u32		level;
+};
+
+static int s2_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+		     enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+	struct s2_walk_data *data = arg;
+
+	data->level = level;
+	data->pteval = *ptep;
+	return 0;
+}
+
+/* Assumes mmu_lock taken */
+static bool __check_ioguard_page(struct kvm_vcpu *vcpu, gpa_t ipa)
+{
+	struct s2_walk_data data;
+	struct kvm_pgtable_walker walker = {
+		.cb             = s2_walker,
+		.flags          = KVM_PGTABLE_WALK_LEAF,
+		.arg            = &data,
+	};
+
+	kvm_pgtable_walk(vcpu->arch.hw_mmu->pgt, ALIGN_DOWN(ipa, PAGE_SIZE),
+			 PAGE_SIZE, &walker);
+
+	/* Must be a PAGE_SIZE mapping with our annotation */
+	return (BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(data.level)) == PAGE_SIZE &&
+		data.pteval == MMIO_NOTE);

Nit: you could do this check in the walker directly and check the return
value of kvm_pgtable_walk() instead. That would allow to get rid of
struct s2_walk_data.

Also, though the compiler might be able to optimize, maybe simplify the
level check to level == (KVM_PGTABLE_MAX_LEVELS - 1)?

Yup, all good points. I guess I could do the same in my other series
that parses the userspace PT to extract the level.

Well, actually, let me take that back. I think something like you have
would be useful, but in pgtable.c directly and re-usable for stage-1 and
stage-2 walks. Maybe something like the below (totally untested)?

I could use such a walker in several places as well in the memory
ownership series:

 - following the idea of [1], I could remove the
   kvm_pgtable_stage2_find_range() function entirely;

 - [2] defines 2 custom walkers that do nothing but walk host stage-2
   and hyp stage-1 page-tables to check permissions and such --  they
   could be removed/re-implemented easily as well.

And you seem to need something similar here, so clearly there is a need.
WDYT?

So FWIW, I've now pushed out an updated series for the THP changes[1],
and you will find a similar patch at the base of the branch. Please
have a look and let me know what you think!

Thanks,

	M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/mmu/mapping-levels

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel