linux-kernel - [RFC PATCH 26/34] gunyah: Share memory parcels

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Message-Id: <20250424141341.841734-27-karim.manaouil@linaro.org>
Date: Thu, 24 Apr 2025 15:13:33 +0100
From: Karim Manaouil <karim.manaouil@...aro.org>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Cc: Karim Manaouil <karim.manaouil@...aro.org>,
	Alexander Graf <graf@...zon.com>,
	Alex Elder <elder@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Fuad Tabba <tabba@...gle.com>,
	Joey Gouly <joey.gouly@....com>,
	Jonathan Corbet <corbet@....net>,
	Marc Zyngier <maz@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
	Quentin Perret <qperret@...gle.com>,
	Rob Herring <robh@...nel.org>,
	Srinivas Kandagatla <srini@...nel.org>,
	Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
	Will Deacon <will@...nel.org>,
	Haripranesh S <haripran@....qualcomm.com>,
	Carl van Schaik <cvanscha@....qualcomm.com>,
	Murali Nalajala <mnalajal@...cinc.com>,
	Sreenivasulu Chalamcharla <sreeniva@....qualcomm.com>,
	Trilok Soni <tsoni@...cinc.com>,
	Stefan Schmidt <stefan.schmidt@...aro.org>
Subject: [RFC PATCH 26/34] gunyah: Share memory parcels

Gunyah Resource Manager sets up a virtual machine based on a device
tree which lives in guest memory. Resource manager requires this memory
to be provided as a memory parcel for it to read and manipulate.
Implement a function to construct a memory parcel from the guest's
pinned memory pages.

Signed-off-by: Karim Manaouil <karim.manaouil@...aro.org>
---
 arch/arm64/kvm/gunyah.c | 80 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/arch/arm64/kvm/gunyah.c b/arch/arm64/kvm/gunyah.c
index 7216db642174..ef0971146b56 100644
--- a/arch/arm64/kvm/gunyah.c
+++ b/arch/arm64/kvm/gunyah.c
@@ -634,6 +634,86 @@ static int gunyah_memory_reclaim_folio(struct gunyah_vm *ghvm,
 	return ret;
 }
 
+static int gunyah_share_memory_parcel(struct gunyah_vm *ghvm,
+		struct gunyah_rm_mem_parcel *parcel, gfn_t gfn, u64 nr)
+{
+	struct kvm *kvm = &ghvm->kvm;
+	struct kvm_memory_slot *memslot;
+	struct page **pages;
+	int ret;
+	u64 i;
+
+	if (!nr)
+		return -EINVAL;
+
+	memslot = gfn_to_memslot(kvm, gfn);
+	if (!memslot)
+		return -ENOENT;
+
+	parcel->mem_entries = kcalloc(nr, sizeof(*parcel->mem_entries), GFP_KERNEL);
+	if (!parcel->mem_entries)
+		return -ENOMEM;
+	parcel->n_mem_entries = nr;
+
+	pages = memslot->arch.pages + (gfn - memslot->base_gfn);
+
+	for (i = 0; i < nr; i++) {
+		parcel->mem_entries[i].size = cpu_to_le64(PAGE_SIZE);
+		parcel->mem_entries[i].phys_addr = cpu_to_le64(page_to_phys(pages[i]));
+	}
+
+	parcel->n_acl_entries = 1;
+	parcel->acl_entries = kcalloc(parcel->n_acl_entries,
+				      sizeof(*parcel->acl_entries), GFP_KERNEL);
+	if (!parcel->n_acl_entries) {
+		ret = -ENOMEM;
+		goto free_entries;
+	}
+	parcel->acl_entries[0].vmid = cpu_to_le16(ghvm->vmid);
+	parcel->acl_entries[0].perms |= GUNYAH_RM_ACL_R;
+	parcel->acl_entries[0].perms |= GUNYAH_RM_ACL_W;
+	parcel->acl_entries[0].perms |= GUNYAH_RM_ACL_X;
+	parcel->mem_handle = GUNYAH_MEM_HANDLE_INVAL;
+
+	ret = gunyah_rm_mem_share(ghvm->rm, parcel);
+	if (ret)
+		goto free_acl;
+
+	return ret;
+free_acl:
+	kfree(parcel->acl_entries);
+	parcel->acl_entries = NULL;
+free_entries:
+	kfree(parcel->mem_entries);
+	parcel->mem_entries = NULL;
+	parcel->n_mem_entries = 0;
+
+	return ret;
+}
+
+static int gunyah_reclaim_memory_parcel(struct gunyah_vm *ghvm,
+		struct gunyah_rm_mem_parcel *parcel, gfn_t gfn, u64 nr)
+{
+	int ret;
+
+	if (parcel->mem_handle != GUNYAH_MEM_HANDLE_INVAL) {
+		ret = gunyah_rm_mem_reclaim(ghvm->rm, parcel);
+		if (ret) {
+			dev_err(ghvm->parent, "Failed to reclaim parcel: %d\n",
+				ret);
+			/* We can't reclaim the pages -- hold onto the pages
+			 * forever because we don't know what state the memory
+			 * is in
+			 */
+			return ret;
+		}
+		parcel->mem_handle = GUNYAH_MEM_HANDLE_INVAL;
+		kfree(parcel->mem_entries);
+		kfree(parcel->acl_entries);
+	}
+	return 0;
+}
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
-- 
2.39.5