linux-kernel - Re: [PATCH v7 5/6] KVM: arm64: Initialize the ptdump parser with stage-2 attributes

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Message-ID: <ZoJsAyrmtge4mXJY@google.com>
Date: Mon, 1 Jul 2024 09:42:43 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
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,
	mark.rutland@....com, maz@...nel.org, 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 v7 5/6] KVM: arm64: Initialize the ptdump parser with
 stage-2 attributes

O Fri, Jun 21, 2024 at 12:32:29PM +0000, 'Sebastian Ene' via kernel-team 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 | 143 ++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 137 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
> index 36dc7662729f..cc1d4fdddc6e 100644
> --- a/arch/arm64/kvm/ptdump.c
> +++ b/arch/arm64/kvm/ptdump.c
> @@ -14,6 +14,61 @@
>  #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 pg_state		parser_state;
> +	struct addr_marker	ipa_marker[MARKERS_LEN];
> +	struct pg_level		level[KVM_PGTABLE_MAX_LEVELS];
> +	struct ptdump_range	range[MARKERS_LEN];
> +};
> +
> +static const struct prot_bits stage2_pte_bits[] = {
> +	{
> +		.mask	= PTE_VALID,
> +		.val	= PTE_VALID,
> +		.set	= " ",
> +		.clear	= "F",
> +	}, {
> +		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
> +		.val	= KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
> +		.set	= "XN",
> +		.clear	= "  ",
> +	}, {
> +		.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_LO_S2_AF | PTE_VALID,
> +		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
> +		.set	= "AF",
> +		.clear	= "  ",
> +	}, {
> +		.mask	= PTE_NG,
> +		.val	= PTE_NG,
> +		.set	= "FnXS",
> +		.clear	= "  ",
> +	}, {
> +		.mask	= PTE_CONT | PTE_VALID,
> +		.val	= PTE_CONT | PTE_VALID,
> +		.set	= "CON",
> +		.clear	= "   ",
> +	}, {
> +		.mask	= PTE_TABLE_BIT,
>
> +		.val	= PTE_TABLE_BIT,
> +		.set	= "   ",
> +		.clear	= "BLK",
> +	},

When doing a kvm_pgtable_stage2_set_owner(), the walker will init a leaf which
has both the table-bit and the valid-bit unset. I believe this would lead to
spurious BLK annotations here.

The following should fix this problem:

  .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 +95,79 @@ static int kvm_ptdump_show_common(struct seq_file *m,
>  	return kvm_pgtable_walk(pgtable, 0, BIT(pgtable->ia_bits), &walker);
>  }
>

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