linux-kernel - Re: [PATCH v8 5/6] KVM: arm64: Initialize the ptdump parser with stage-2 attributes

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Message-ID: <86plq3xoly.wl-maz@kernel.org>
Date: Tue, 20 Aug 2024 15:20:25 +0100
From: Marc Zyngier <maz@...nel.org>
To: Sebastian Ene <sebastianene@...gle.com>
Cc: akpm@...ux-foundation.org,
	alexghiti@...osinc.com,
	ankita@...dia.com,
	ardb@...nel.org,
	catalin.marinas@....com,
	christophe.leroy@...roup.eu,
	james.morse@....com,
	vdonnefort@...gle.com,
	mark.rutland@....com,
	oliver.upton@...ux.dev,
	rananta@...gle.com,
	ryan.roberts@....com,
	shahuang@...hat.com,
	suzuki.poulose@....com,
	will@...nel.org,
	yuzenghui@...wei.com,
	kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	kernel-team@...roid.com
Subject: Re: [PATCH v8 5/6] KVM: arm64: Initialize the ptdump parser with stage-2 attributes

On Fri, 16 Aug 2024 13:39:05 +0100,
Sebastian Ene <sebastianene@...gle.com> wrote:
> 
> Define a set of attributes used by the ptdump parser to display the
> properties of a guest memory region covered by a pagetable descriptor.
> Build a description of the pagetable levels and initialize the parser
> with this configuration.
> 
> Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
> ---
>  arch/arm64/kvm/ptdump.c | 135 ++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 129 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
> index 52483d56be2e..79be07ec3c3c 100644
> --- a/arch/arm64/kvm/ptdump.c
> +++ b/arch/arm64/kvm/ptdump.c
> @@ -14,6 +14,51 @@
>  #include <kvm_ptdump.h>
>  
>  
> +#define MARKERS_LEN		(2)
> +#define KVM_PGTABLE_MAX_LEVELS	(KVM_PGTABLE_LAST_LEVEL + 1)
> +
> +struct kvm_ptdump_guest_state {
> +	struct kvm		*kvm;
> +	struct ptdump_pg_state	parser_state;
> +	struct addr_marker	ipa_marker[MARKERS_LEN];
> +	struct ptdump_pg_level	level[KVM_PGTABLE_MAX_LEVELS];
> +	struct ptdump_range	range[MARKERS_LEN];
> +};
> +
> +static const struct ptdump_prot_bits stage2_pte_bits[] = {
> +	{
> +		.mask	= PTE_VALID,
> +		.val	= PTE_VALID,
> +		.set	= " ",
> +		.clear	= "F",
> +	}, {
> +		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
> +		.set	= "R",
> +		.clear	= " ",
> +	}, {
> +		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
> +		.set	= "W",
> +		.clear	= " ",
> +	}, {
> +		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
> +		.val	= PTE_VALID,
> +		.set	= " ",
> +		.clear	= "X",
> +	}, {
> +		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
> +		.set	= "AF",
> +		.clear	= "  ",
> +	}, {
> +		.mask	= PTE_TABLE_BIT | PTE_VALID,
> +		.val	= PTE_VALID,
> +		.set	= "BLK",
> +		.clear	= "   ",
> +	},
> +};
> +
>  static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx,
>  			      enum kvm_pgtable_walk_flags visit)
>  {
> @@ -40,15 +85,81 @@ static int kvm_ptdump_show_common(struct seq_file *m,
>  	return kvm_pgtable_walk(pgtable, 0, BIT(pgtable->ia_bits), &walker);
>  }
>  
> +static int kvm_ptdump_build_levels(struct ptdump_pg_level *level, u32 start_lvl)
> +{
> +	static const char * const level_names[] = {"PGD", "PUD", "PMD", "PTE"};

How about 5 level page tables, which we support since v6.8? The
architecture uses a SL=-1 in this case, and I have the feeling this is
going to expose in a lovely way, given that you use a u32 for
start_level... :-/

I also question the use of these names, which have no relation with
what the architecture describes (news flash, arm64 isn't just another
x86 implementation ;-).

I'd rather this displays the actual level, which is something anyone
can understand.

I think this needs some surgery to handle FEAT_LVA2 properly.

Thanks,

	M.

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