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

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Message-ID: <ZsM4MacbOe7GLIKl@google.com>
Date: Mon, 19 Aug 2024 12:18:57 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: Vincent Donnefort <vdonnefort@...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 v8 5/6] KVM: arm64: Initialize the ptdump parser with
 stage-2 attributes

On Mon, Aug 19, 2024 at 11:28:19AM +0100, Vincent Donnefort wrote:
> 
> [...]
> 
> > +static int kvm_ptdump_build_levels(struct ptdump_pg_level *level, u32 start_lvl)
> > +{
> > +	static const char * const level_names[] = {"PGD", "PUD", "PMD", "PTE"};
> > +	u32 i = 0;
> > +	u64 mask = 0;
> > +
> > +	if (start_lvl > 2) {
> > +		pr_err("invalid start_lvl %u\n", start_lvl);
> > +		return -EINVAL;
> > +	}
> 
> It looks like a duplicate of the if below.

I will drop this.

> 
> > +
> > +	if (WARN_ON_ONCE(start_lvl >= KVM_PGTABLE_LAST_LEVEL))
> > +		return -EINVAL;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(stage2_pte_bits); i++)
> > +		mask |= stage2_pte_bits[i].mask;
> > +
> > +	for (i = start_lvl; i < KVM_PGTABLE_MAX_LEVELS; i++) {
> > +		strscpy(level[i].name, level_names[i], sizeof(level[i].name));
> > +
> > +		level[i].num	= ARRAY_SIZE(stage2_pte_bits);
> > +		level[i].bits	= stage2_pte_bits;
> > +		level[i].mask	= mask;
> > +	}
> > +
> > +	if (start_lvl > 0)
> > +		strscpy(level[start_lvl].name, "PGD", sizeof(level[start_lvl].name));
> > +
> > +	return 0;
> > +}
> > +
> > +static struct kvm_ptdump_guest_state
> > +*kvm_ptdump_parser_init(struct kvm *kvm)
> 
> nit: I guess it's more a "create" than an "init" as we allocate the memory.

Yes, that should work as well.

> 
> > +{
> > +	struct kvm_ptdump_guest_state *st;
> > +	struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
> > +	struct kvm_pgtable *pgtable = mmu->pgt;
> > +	int ret;
> > +
> > +	st = kzalloc(sizeof(struct kvm_ptdump_guest_state), GFP_KERNEL_ACCOUNT);
> > +	if (!st)
> > +		return NULL;
> 
> return ERR_PTR(-ENOMEM); ?

Yep, we can encode the ENOMEM in the ptr.

> 
> > +
> > +	ret = kvm_ptdump_build_levels(&st->level[0], pgtable->start_level);
> > +	if (ret) {
> > +		kfree(st);
> > +		return ERR_PTR(ret);
> > +	}
> > +
> > +	st->ipa_marker[0].name		= "Guest IPA";
> > +	st->ipa_marker[1].start_address = BIT(pgtable->ia_bits);
> > +	st->range[0].end		= BIT(pgtable->ia_bits);
> > +
> > +	st->kvm				= kvm;
> > +	st->parser_state = (struct ptdump_pg_state) {
> > +		.marker		= &st->ipa_marker[0],
> > +		.level		= -1,
> > +		.pg_level	= &st->level[0],
> > +		.ptdump.range	= &st->range[0],
> > +	};
> > +
> > +	return st;
> > +}
> > +
> 
> [...]

Thanks,
Seb