Re: [PATCH 1/3] KVM: arm64: Don't defer TLB invalidation when zapping table entries

From: Oliver Upton <oliver.upton@linux.dev>
To: Will Deacon <will@kernel.org>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Gavin Shan <gshan@redhat.com>, Marc Zyngier <maz@kernel.org>,
	Mostafa Saleh <smostafa@google.com>,
	Quentin Perret <qperret@google.com>,
	Raghavendra Rao Ananta <rananta@google.com>,
	Ryan Roberts <ryan.roberts@arm.com>,
	Shaoqin Huang <shahuang@redhat.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH 1/3] KVM: arm64: Don't defer TLB invalidation when zapping table entries
Date: Tue, 26 Mar 2024 09:14:33 -0700	[thread overview]
Message-ID: <ZgL0ae7AffPUw4CS@linux.dev> (raw)
In-Reply-To: <20240326161000.GA9723@willie-the-truck>

On Tue, Mar 26, 2024 at 04:10:01PM +0000, Will Deacon wrote:
> > @@ -1163,7 +1168,7 @@ static int stage2_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
> >  					       kvm_granule_size(ctx->level));
> >  
> >  	if (childp)
> > -		mm_ops->put_page(childp);
> > +		mm_ops->free_unlinked_table(childp, ctx->level);
> 
> Hmm, but doesn't the deferred TLBI still happen after the RCU critical
> section?

Right... We'd need to change that too :) Although I suppose table
invalidations are relatively infrequent when compared to leaf
invalidations.

> I also think I found another bug, so I'll send a v2 with an extra patch...

And I'm sure there's plenty more to be found too, heh.

-- 
Thanks,
Oliver