From: Will Deacon <will@kernel.org>
To: Quentin Perret <qperret@google.com>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
kernel-team@android.com
Subject: Re: [PATCH v3 08/15] KVM: arm64: pkvm: Refcount the pages shared with EL2
Date: Thu, 9 Dec 2021 11:16:09 +0000 [thread overview]
Message-ID: <20211209111609.GC1912@willie-the-truck> (raw)
In-Reply-To: <20211201170411.1561936-9-qperret@google.com>
On Wed, Dec 01, 2021 at 05:04:02PM +0000, Quentin Perret wrote:
> In order to simplify the page tracking infrastructure at EL2 in nVHE
> protected mode, move the responsibility of refcounting pages that are
> shared multiple times on the host. In order to do so, let's create a
> red-black tree tracking all the PFNs that have been shared, along with
> a refcount.
>
> Signed-off-by: Quentin Perret <qperret@google.com>
> ---
> arch/arm64/kvm/mmu.c | 78 ++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 68 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index fd868fb9d922..d72566896755 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -284,23 +284,72 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
> }
> }
>
> -static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
> +struct hyp_shared_pfn {
> + u64 pfn;
> + int count;
> + struct rb_node node;
> +};
> +
> +static DEFINE_MUTEX(hyp_shared_pfns_lock);
> +static struct rb_root hyp_shared_pfns = RB_ROOT;
> +
> +static struct hyp_shared_pfn *find_shared_pfn(u64 pfn, struct rb_node ***node,
> + struct rb_node **parent)
> {
> - phys_addr_t addr;
> - int ret;
> + struct hyp_shared_pfn *this;
> +
> + *node = &hyp_shared_pfns.rb_node;
> + *parent = NULL;
> + while (**node) {
> + this = container_of(**node, struct hyp_shared_pfn, node);
> + *parent = **node;
> + if (this->pfn < pfn)
> + *node = &((**node)->rb_left);
> + else if (this->pfn > pfn)
> + *node = &((**node)->rb_right);
> + else
> + return this;
> + }
>
> - for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
> - ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
> - __phys_to_pfn(addr));
> - if (ret)
> - return ret;
> + return NULL;
> +}
> +
> +static int share_pfn_hyp(u64 pfn)
> +{
> + struct rb_node **node, *parent;
> + struct hyp_shared_pfn *this;
> + int ret = 0;
> +
> + mutex_lock(&hyp_shared_pfns_lock);
> + this = find_shared_pfn(pfn, &node, &parent);
I don't think this is a fast-path at the moment, but in the future we might
consider using RCU to do the lookup outside of the mutex.
But as-is:
Acked-by: Will Deacon <will@kernel.org>
Will
next prev parent reply other threads:[~2021-12-09 11:16 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-01 17:03 [PATCH v3 00/15] KVM: arm64: Introduce kvm_share_hyp() Quentin Perret
2021-12-01 17:03 ` [PATCH v3 01/15] KVM: arm64: Check if running in VHE from kvm_host_owns_hyp_mappings() Quentin Perret
2021-12-09 10:10 ` Will Deacon
2021-12-10 13:37 ` Quentin Perret
2021-12-01 17:03 ` [PATCH v3 02/15] KVM: arm64: Provide {get,put}_page() stubs for early hyp allocator Quentin Perret
2021-12-09 10:12 ` Will Deacon
2021-12-01 17:03 ` [PATCH v3 03/15] KVM: arm64: Refcount hyp stage-1 pgtable pages Quentin Perret
2021-12-09 10:29 ` Will Deacon
2021-12-10 14:34 ` Quentin Perret
2021-12-13 12:53 ` Will Deacon
2021-12-01 17:03 ` [PATCH v3 04/15] KVM: arm64: Fixup hyp stage-1 refcount Quentin Perret
2021-12-09 11:09 ` Will Deacon
2021-12-01 17:03 ` [PATCH v3 05/15] KVM: arm64: Hook up ->page_count() for hypervisor stage-1 page-table Quentin Perret
2021-12-01 17:04 ` [PATCH v3 06/15] KVM: arm64: Implement kvm_pgtable_hyp_unmap() at EL2 Quentin Perret
2021-12-07 14:47 ` Andrew Walbran
2021-12-08 9:51 ` Quentin Perret
2021-12-08 14:40 ` Andrew Walbran
2021-12-15 16:02 ` Quentin Perret
2021-12-01 17:04 ` [PATCH v3 07/15] KVM: arm64: Introduce kvm_share_hyp() Quentin Perret
2021-12-09 11:13 ` Will Deacon
2021-12-10 14:37 ` Quentin Perret
2021-12-01 17:04 ` [PATCH v3 08/15] KVM: arm64: pkvm: Refcount the pages shared with EL2 Quentin Perret
2021-12-09 11:16 ` Will Deacon [this message]
2021-12-01 17:04 ` [PATCH v3 09/15] KVM: arm64: Extend pkvm_page_state enumeration to handle absent pages Quentin Perret
2021-12-14 14:47 ` Andrew Walbran
2021-12-01 17:04 ` [PATCH v3 10/15] KVM: arm64: Introduce wrappers for host and hyp spin lock accessors Quentin Perret
2021-12-14 14:48 ` Andrew Walbran
2021-12-14 14:52 ` Will Deacon
2021-12-01 17:04 ` [PATCH v3 11/15] KVM: arm64: Implement do_share() helper for sharing memory Quentin Perret
2021-12-10 15:18 ` Andrew Walbran
2021-12-01 17:04 ` [PATCH v3 12/15] KVM: arm64: Implement __pkvm_host_share_hyp() using do_share() Quentin Perret
2021-12-01 17:04 ` [PATCH v3 13/15] KVM: arm64: Implement do_unshare() helper for unsharing memory Quentin Perret
2021-12-10 15:08 ` Andrew Walbran
2021-12-01 17:04 ` [PATCH v3 14/15] KVM: arm64: Expose unshare hypercall to the host Quentin Perret
2021-12-01 17:04 ` [PATCH v3 15/15] KVM: arm64: pkvm: Unshare guest structs during teardown Quentin Perret
2021-12-09 11:22 ` Will Deacon
2021-12-10 14:48 ` Quentin Perret
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