KVM: arm64: FF-A proxy for pKVM

new file mode 100644
index 000000000000..fc09ec671e24
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2022 - Google LLC
+ * Author: Andrew Walbran <[email protected]>
+ */
+#ifndef __KVM_HYP_FFA_H
+#define __KVM_HYP_FFA_H
+
+#include <asm/kvm_host.h>
+
+#define FFA_MIN_FUNC_NUM 0x60
+#define FFA_MAX_FUNC_NUM 0x7F
+
+bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt);
+
+#endif /* __KVM_HYP_FFA_H */

106 lines not on this page · raw message

index 728e01d4536b..223611e43279 100644
@@ -13,6 +13,7 @@
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 
+#include <nvhe/ffa.h>
 #include <nvhe/mem_protect.h>
 #include <nvhe/mm.h>
 #include <nvhe/pkvm.h>

@@ -373,6 +374,8 @@ static void handle_host_smc(struct kvm_cpu_context *host_ctxt)
 	bool handled;
 
 	handled = kvm_host_psci_handler(host_ctxt);
+	if (!handled)
+		handled = kvm_host_ffa_handler(host_ctxt);
 	if (!handled)
 		default_host_smc_handler(host_ctxt);
 

index bcd774d74f34..b7fe6e829231 100644
@@ -391,6 +391,7 @@ struct kvm_host_data {
 struct kvm_host_psci_config {
 	/* PSCI version used by host. */
 	u32 version;
+	u32 smccc_version;
 
 	/* Function IDs used by host if version is v0.1. */
 	struct psci_0_1_function_ids function_ids_0_1;

index 4b2e16e696a8..3dab9a33e9f8 100644
@@ -1790,6 +1790,7 @@ static bool __init init_psci_relay(void)
 	}
 
 	kvm_host_psci_config.version = psci_ops.get_version();
+	kvm_host_psci_config.smccc_version = arm_smccc_get_version();
 
 	if (kvm_host_psci_config.version == PSCI_VERSION(0, 1)) {
 		kvm_host_psci_config.function_ids_0_1 = get_psci_0_1_function_ids();

index fc09ec671e24..5c9b92430ff3 100644
@@ -11,6 +11,7 @@
 #define FFA_MIN_FUNC_NUM 0x60
 #define FFA_MAX_FUNC_NUM 0x7F
 
+int hyp_ffa_init(void);
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt);
 
 #endif /* __KVM_HYP_FFA_H */

index a437b0727881..b387e433f15e 100644
@@ -31,6 +31,12 @@
 #include <nvhe/ffa.h>
 #include <nvhe/trap_handler.h>
 
+/*
+ * "ID value 0 must be returned at the Non-secure physical FF-A instance"
+ * We share this ID with the host.
+ */
+#define HOST_FFA_ID	0
+
 static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 {
 	*res = (struct arm_smccc_res) {

@@ -104,3 +110,27 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 	ffa_set_retval(host_ctxt, &res);
 	return true;
 }
+
+int hyp_ffa_init(void)
+{
+	struct arm_smccc_res res;
+
+	if (kvm_host_psci_config.smccc_version < ARM_SMCCC_VERSION_1_2)
+		return 0;
+
+	arm_smccc_1_1_smc(FFA_VERSION, FFA_VERSION_1_0, 0, 0, 0, 0, 0, 0, &res);
+	if (res.a0 == FFA_RET_NOT_SUPPORTED)
+		return 0;
+
+	if (res.a0 != FFA_VERSION_1_0)
+		return -EOPNOTSUPP;
+
+	arm_smccc_1_1_smc(FFA_ID_GET, 0, 0, 0, 0, 0, 0, 0, &res);
+	if (res.a0 != FFA_SUCCESS)
+		return -EOPNOTSUPP;
+
+	if (res.a2 != HOST_FFA_ID)
+		return -EINVAL;
+
+	return 0;
+}

index 110f04627785..c4ca174a0592 100644
@@ -11,6 +11,7 @@
 #include <asm/kvm_pkvm.h>
 
 #include <nvhe/early_alloc.h>
+#include <nvhe/ffa.h>
 #include <nvhe/fixed_config.h>
 #include <nvhe/gfp.h>
 #include <nvhe/memory.h>

@@ -314,6 +315,10 @@ void __noreturn __pkvm_init_finalise(void)
 	if (ret)
 		goto out;
 
+	ret = hyp_ffa_init();
+	if (ret)
+		goto out;
+
 	pkvm_hyp_vm_table_init(vm_table_base);
 out:
 	/*

index 01129b0d4c68..2b495ec59deb 100644
@@ -106,4 +106,12 @@ static inline unsigned long host_s2_pgtable_pages(void)
 	return res;
 }
 
+#define KVM_FFA_MBOX_NR_PAGES	1
+
+static inline unsigned long hyp_ffa_proxy_pages(void)
+{
+	/* A page each for the hypervisor's RX and TX mailboxes. */
+	return 2 * KVM_FFA_MBOX_NR_PAGES;
+}
+
 #endif	/* __ARM64_KVM_PKVM_H__ */

index 5c9b92430ff3..1becb10ecd80 100644
@@ -11,7 +11,7 @@
 #define FFA_MIN_FUNC_NUM 0x60
 #define FFA_MAX_FUNC_NUM 0x7F
 
-int hyp_ffa_init(void);
+int hyp_ffa_init(void *pages);
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt);
 
 #endif /* __KVM_HYP_FFA_H */

index b387e433f15e..de0fba79b195 100644
@@ -28,8 +28,11 @@
 
 #include <linux/arm-smccc.h>
 #include <linux/arm_ffa.h>
+#include <asm/kvm_pkvm.h>
+
 #include <nvhe/ffa.h>
 #include <nvhe/trap_handler.h>
+#include <nvhe/spinlock.h>
 
 /*
  * "ID value 0 must be returned at the Non-secure physical FF-A instance"

@@ -37,6 +40,19 @@
  */
 #define HOST_FFA_ID	0
 
+struct kvm_ffa_buffers {
+	hyp_spinlock_t lock;
+	void *tx;
+	void *rx;
+};
+
+/*
+ * Note that we don't currently lock these buffers explicitly, instead
+ * relying on the locking of the host FFA buffers as we only have one
+ * client.
+ */
+static struct kvm_ffa_buffers hyp_buffers;
+
 static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 {
 	*res = (struct arm_smccc_res) {

@@ -111,7 +127,7 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 	return true;
 }
 
-int hyp_ffa_init(void)
+int hyp_ffa_init(void *pages)
 {
 	struct arm_smccc_res res;
 

@@ -132,5 +148,11 @@ int hyp_ffa_init(void)
 	if (res.a2 != HOST_FFA_ID)
 		return -EINVAL;
 
+	hyp_buffers = (struct kvm_ffa_buffers) {
+		.lock	= __HYP_SPIN_LOCK_UNLOCKED,
+		.tx	= pages,
+		.rx	= pages + (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE),
+	};
+
 	return 0;
 }

index c4ca174a0592..bb98630dfeaf 100644
@@ -29,6 +29,7 @@ static void *vmemmap_base;
 static void *vm_table_base;
 static void *hyp_pgt_base;
 static void *host_s2_pgt_base;
+static void *ffa_proxy_pages;
 static struct kvm_pgtable_mm_ops pkvm_pgtable_mm_ops;
 static struct hyp_pool hpool;
 

@@ -58,6 +59,11 @@ static int divide_memory_pool(void *virt, unsigned long size)
 	if (!host_s2_pgt_base)
 		return -ENOMEM;
 
+	nr_pages = hyp_ffa_proxy_pages();
+	ffa_proxy_pages = hyp_early_alloc_contig(nr_pages);
+	if (!ffa_proxy_pages)
+		return -ENOMEM;
+
 	return 0;
 }
 

@@ -315,7 +321,7 @@ void __noreturn __pkvm_init_finalise(void)
 	if (ret)
 		goto out;
 
-	ret = hyp_ffa_init();
+	ret = hyp_ffa_init(ffa_proxy_pages);
 	if (ret)
 		goto out;
 

index cf56958b1492..bb405e274df6 100644
@@ -74,6 +74,7 @@ void __init kvm_hyp_reserve(void)
 	hyp_mem_pages += host_s2_pgtable_pages();
 	hyp_mem_pages += hyp_vm_table_pages();
 	hyp_mem_pages += hyp_vmemmap_pages(STRUCT_HYP_PAGE_SIZE);
+	hyp_mem_pages += hyp_ffa_proxy_pages();
 
 	/*
 	 * Try to allocate a PMD-aligned region to reduce TLB pressure once

index de0fba79b195..9ee3be517e1e 100644
@@ -31,6 +31,8 @@
 #include <asm/kvm_pkvm.h>
 
 #include <nvhe/ffa.h>
+#include <nvhe/mem_protect.h>
+#include <nvhe/memory.h>
 #include <nvhe/trap_handler.h>
 #include <nvhe/spinlock.h>
 

@@ -52,6 +54,7 @@ struct kvm_ffa_buffers {
  * client.
  */
 static struct kvm_ffa_buffers hyp_buffers;
+static struct kvm_ffa_buffers host_buffers;
 
 static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 {

@@ -61,6 +64,15 @@ static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 	};
 }
 
+static void ffa_to_smccc_res(struct arm_smccc_res *res, int ret)
+{
+	if (ret == FFA_RET_SUCCESS) {
+		*res = (struct arm_smccc_res) { .a0 = FFA_SUCCESS };
+	} else {
+		ffa_to_smccc_error(res, ret);
+	}
+}
+
 static void ffa_set_retval(struct kvm_cpu_context *ctxt,
 			   struct arm_smccc_res *res)
 {

@@ -78,6 +90,140 @@ static bool is_ffa_call(u64 func_id)
 	       ARM_SMCCC_FUNC_NUM(func_id) <= FFA_MAX_FUNC_NUM;
 }
 
+static int spmd_map_ffa_buffers(u64 ffa_page_count)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_1_1_smc(FFA_FN64_RXTX_MAP,
+			  hyp_virt_to_phys(hyp_buffers.tx),
+			  hyp_virt_to_phys(hyp_buffers.rx),
+			  ffa_page_count,
+			  0, 0, 0, 0,
+			  &res);
+
+	return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
+}
+
+static int spmd_unmap_ffa_buffers(void)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_1_1_smc(FFA_RXTX_UNMAP,
+			  HOST_FFA_ID,
+			  0, 0, 0, 0, 0, 0,
+			  &res);
+
+	return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
+}
+
+static void do_ffa_rxtx_map(struct arm_smccc_res *res,
+			    struct kvm_cpu_context *ctxt)
+{
+	DECLARE_REG(phys_addr_t, tx, ctxt, 1);
+	DECLARE_REG(phys_addr_t, rx, ctxt, 2);
+	DECLARE_REG(u32, npages, ctxt, 3);
+	int ret = 0;
+	void *rx_virt, *tx_virt;
+
+	if (npages != (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) / FFA_PAGE_SIZE) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
+	if (!PAGE_ALIGNED(tx) || !PAGE_ALIGNED(rx)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
+	hyp_spin_lock(&host_buffers.lock);
+	if (host_buffers.tx) {
+		ret = FFA_RET_DENIED;
+		goto out_unlock;
+	}
+
+	ret = spmd_map_ffa_buffers(npages);
+	if (ret)
+		goto out_unlock;
+
+	ret = __pkvm_host_share_hyp(hyp_phys_to_pfn(tx));
+	if (ret) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto err_unmap;
+	}
+
+	ret = __pkvm_host_share_hyp(hyp_phys_to_pfn(rx));
+	if (ret) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto err_unshare_tx;
+	}
+
+	tx_virt = hyp_phys_to_virt(tx);
+	ret = hyp_pin_shared_mem(tx_virt, tx_virt + 1);
+	if (ret) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto err_unshare_rx;
+	}
+
+	rx_virt = hyp_phys_to_virt(rx);
+	ret = hyp_pin_shared_mem(rx_virt, rx_virt + 1);
+	if (ret) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto err_unpin_tx;
+	}
+
+	host_buffers.tx = tx_virt;
+	host_buffers.rx = rx_virt;
+
+out_unlock:
+	hyp_spin_unlock(&host_buffers.lock);
+out:
+	ffa_to_smccc_res(res, ret);
+	return;
+
+err_unpin_tx:
+	hyp_unpin_shared_mem(tx_virt, tx_virt + 1);
+err_unshare_rx:
+	__pkvm_host_unshare_hyp(hyp_phys_to_pfn(rx));
+err_unshare_tx:
+	__pkvm_host_unshare_hyp(hyp_phys_to_pfn(tx));
+err_unmap:
+	spmd_unmap_ffa_buffers();
+	goto out_unlock;
+}
+
+static void do_ffa_rxtx_unmap(struct arm_smccc_res *res,
+			      struct kvm_cpu_context *ctxt)
+{
+	DECLARE_REG(u32, id, ctxt, 1);
+	int ret = 0;
+
+	if (id != HOST_FFA_ID) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
+	hyp_spin_lock(&host_buffers.lock);
+	if (!host_buffers.tx) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out_unlock;
+	}
+
+	hyp_unpin_shared_mem(host_buffers.tx, host_buffers.tx + 1);
+	WARN_ON(__pkvm_host_unshare_hyp(hyp_virt_to_pfn(host_buffers.tx)));
+	host_buffers.tx = NULL;
+
+	hyp_unpin_shared_mem(host_buffers.rx, host_buffers.rx + 1);
+	WARN_ON(__pkvm_host_unshare_hyp(hyp_virt_to_pfn(host_buffers.rx)));
+	host_buffers.rx = NULL;
+
+	spmd_unmap_ffa_buffers();
+
+out_unlock:
+	hyp_spin_unlock(&host_buffers.lock);
+out:
+	ffa_to_smccc_res(res, ret);
+}
+
 /*
  * Is a given FFA function supported, either by forwarding on directly
  * or by handling at EL2?

@@ -119,10 +265,21 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 	if (!is_ffa_call(func_id))
 		return false;
 
+	switch (func_id) {
+	/* Memory management */
+	case FFA_FN64_RXTX_MAP:
+		do_ffa_rxtx_map(&res, host_ctxt);
+		goto out_handled;
+	case FFA_RXTX_UNMAP:
+		do_ffa_rxtx_unmap(&res, host_ctxt);
+		goto out_handled;
+	}
+
 	if (ffa_call_supported(func_id))
 		return false; /* Pass through */
 
 	ffa_to_smccc_error(&res, FFA_RET_NOT_SUPPORTED);
+out_handled:
 	ffa_set_retval(host_ctxt, &res);
 	return true;
 }

@@ -130,6 +287,7 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 int hyp_ffa_init(void *pages)
 {
 	struct arm_smccc_res res;
+	size_t min_rxtx_sz;
 
 	if (kvm_host_psci_config.smccc_version < ARM_SMCCC_VERSION_1_2)
 		return 0;

@@ -148,11 +306,37 @@ int hyp_ffa_init(void *pages)
 	if (res.a2 != HOST_FFA_ID)
 		return -EINVAL;
 
+	arm_smccc_1_1_smc(FFA_FEATURES, FFA_FN64_RXTX_MAP,
+			  0, 0, 0, 0, 0, 0, &res);
+	if (res.a0 != FFA_SUCCESS)
+		return -EOPNOTSUPP;
+
+	switch (res.a2) {
+	case FFA_FEAT_RXTX_MIN_SZ_4K:
+		min_rxtx_sz = SZ_4K;
+		break;
+	case FFA_FEAT_RXTX_MIN_SZ_16K:
+		min_rxtx_sz = SZ_16K;
+		break;
+	case FFA_FEAT_RXTX_MIN_SZ_64K:
+		min_rxtx_sz = SZ_64K;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (min_rxtx_sz > PAGE_SIZE)
+		return -EOPNOTSUPP;
+
 	hyp_buffers = (struct kvm_ffa_buffers) {
 		.lock	= __HYP_SPIN_LOCK_UNLOCKED,
 		.tx	= pages,
 		.rx	= pages + (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE),
 	};
 
+	host_buffers = (struct kvm_ffa_buffers) {
+		.lock	= __HYP_SPIN_LOCK_UNLOCKED,
+	};
+
 	return 0;
 }

index c87aeecaa9b2..b9f81035eb41 100644
@@ -94,6 +94,14 @@
  */
 #define FFA_PAGE_SIZE		SZ_4K
 
+/*
+ * Minimum buffer size/alignment encodings returned by an FFA_FEATURES
+ * query for FFA_RXTX_MAP.
+ */
+#define FFA_FEAT_RXTX_MIN_SZ_4K		0
+#define FFA_FEAT_RXTX_MIN_SZ_64K	1
+#define FFA_FEAT_RXTX_MIN_SZ_16K	2
+
 /* FFA Bus/Device/Driver related */
 struct ffa_device {
 	int vm_id;

index b7bdbe63deed..0972faccc2af 100644
@@ -57,6 +57,7 @@ extern struct host_mmu host_mmu;
 enum pkvm_component_id {
 	PKVM_ID_HOST,
 	PKVM_ID_HYP,
+	PKVM_ID_FFA,
 };
 
 extern unsigned long hyp_nr_cpus;

@@ -66,6 +67,8 @@ int __pkvm_host_share_hyp(u64 pfn);
 int __pkvm_host_unshare_hyp(u64 pfn);
 int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
 int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
+int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
+int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
 
 bool addr_is_memory(phys_addr_t phys);
 int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);

95 lines not on this page · raw message

index 9ee3be517e1e..95bc70e52e91 100644
@@ -116,6 +116,14 @@ static int spmd_unmap_ffa_buffers(void)
 	return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
 }
 
+static void spmd_mem_share(struct arm_smccc_res *res, u32 len, u32 fraglen)
+{
+	arm_smccc_1_1_smc(FFA_FN64_MEM_SHARE,
+			  len, fraglen,
+			  0, 0, 0, 0, 0,
+			  res);
+}
+
 static void do_ffa_rxtx_map(struct arm_smccc_res *res,
 			    struct kvm_cpu_context *ctxt)
 {

@@ -224,6 +232,149 @@ static void do_ffa_rxtx_unmap(struct arm_smccc_res *res,
 	ffa_to_smccc_res(res, ret);
 }
 
+static u32 __ffa_host_share_ranges(struct ffa_mem_region_addr_range *ranges,
+				   u32 nranges)
+{
+	u32 i;
+
+	for (i = 0; i < nranges; ++i) {
+		struct ffa_mem_region_addr_range *range = &ranges[i];
+		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
+		u64 pfn = hyp_phys_to_pfn(range->address);
+
+		if (!PAGE_ALIGNED(sz))
+			break;
+
+		if (__pkvm_host_share_ffa(pfn, sz / PAGE_SIZE))
+			break;
+	}
+
+	return i;
+}
+
+static u32 __ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
+				     u32 nranges)
+{
+	u32 i;
+
+	for (i = 0; i < nranges; ++i) {
+		struct ffa_mem_region_addr_range *range = &ranges[i];
+		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
+		u64 pfn = hyp_phys_to_pfn(range->address);
+
+		if (!PAGE_ALIGNED(sz))
+			break;
+
+		if (__pkvm_host_unshare_ffa(pfn, sz / PAGE_SIZE))
+			break;
+	}
+
+	return i;
+}
+
+static int ffa_host_share_ranges(struct ffa_mem_region_addr_range *ranges,
+				 u32 nranges)
+{
+	u32 nshared = __ffa_host_share_ranges(ranges, nranges);
+	int ret = 0;
+
+	if (nshared != nranges) {
+		WARN_ON(__ffa_host_unshare_ranges(ranges, nshared) != nshared);
+		ret = FFA_RET_DENIED;
+	}
+
+	return ret;
+}
+
+static int ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
+				   u32 nranges)
+{
+	u32 nunshared = __ffa_host_unshare_ranges(ranges, nranges);
+	int ret = 0;
+
+	if (nunshared != nranges) {
+		WARN_ON(__ffa_host_share_ranges(ranges, nunshared) != nunshared);
+		ret = FFA_RET_DENIED;
+	}
+
+	return ret;
+}
+
+static void do_ffa_mem_share(struct arm_smccc_res *res,
+			     struct kvm_cpu_context *ctxt)
+{
+	DECLARE_REG(u32, len, ctxt, 1);
+	DECLARE_REG(u32, fraglen, ctxt, 2);
+	DECLARE_REG(u64, addr_mbz, ctxt, 3);
+	DECLARE_REG(u32, npages_mbz, ctxt, 4);
+	struct ffa_composite_mem_region *reg;
+	struct ffa_mem_region *buf;
+	int ret = 0;
+	u32 offset;
+
+	if (addr_mbz || npages_mbz || fraglen > len ||
+	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
+	if (fraglen < len) {
+		ret = FFA_RET_ABORTED;
+		goto out;
+	}
+
+	if (fraglen < sizeof(struct ffa_mem_region) +
+		      sizeof(struct ffa_mem_region_attributes)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
+	hyp_spin_lock(&host_buffers.lock);
+	if (!host_buffers.tx) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out_unlock;
+	}
+
+	buf = hyp_buffers.tx;
+	memcpy(buf, host_buffers.tx, fraglen);
+
+	offset = buf->ep_mem_access[0].composite_off;
+	if (!offset || buf->ep_count != 1 || buf->sender_id != HOST_FFA_ID) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out_unlock;
+	}
+
+	if (fraglen < offset + sizeof(struct ffa_composite_mem_region)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out_unlock;
+	}
+
+	reg = (void *)buf + offset;
+	if (fraglen < offset + sizeof(struct ffa_composite_mem_region) +
+		      reg->addr_range_cnt *
+		      sizeof(struct ffa_mem_region_addr_range)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out_unlock;
+	}
+
+	ret = ffa_host_share_ranges(reg->constituents, reg->addr_range_cnt);
+	if (ret)
+		goto out_unlock;
+
+	spmd_mem_share(res, len, fraglen);
+	if (res->a0 != FFA_SUCCESS) {
+		WARN_ON(ffa_host_unshare_ranges(reg->constituents,
+						reg->addr_range_cnt));
+	}
+
+out_unlock:
+	hyp_spin_unlock(&host_buffers.lock);
+out:
+	if (ret)
+		ffa_to_smccc_res(res, ret);
+	return;
+}
+
 /*
  * Is a given FFA function supported, either by forwarding on directly
  * or by handling at EL2?

@@ -273,6 +424,10 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 	case FFA_RXTX_UNMAP:
 		do_ffa_rxtx_unmap(&res, host_ctxt);
 		goto out_handled;
+	case FFA_MEM_SHARE:
+	case FFA_FN64_MEM_SHARE:
+		do_ffa_mem_share(&res, host_ctxt);
+		goto out_handled;
 	}
 
 	if (ffa_call_supported(func_id))

index 95bc70e52e91..b23e3869ce63 100644
@@ -124,6 +124,23 @@ static void spmd_mem_share(struct arm_smccc_res *res, u32 len, u32 fraglen)
 			  res);
 }
 
+static void spmd_mem_reclaim(struct arm_smccc_res *res, u32 handle_lo,
+			     u32 handle_hi, u32 flags)
+{
+	arm_smccc_1_1_smc(FFA_MEM_RECLAIM,
+			  handle_lo, handle_hi, flags,
+			  0, 0, 0, 0,
+			  res);
+}
+
+static void spmd_retrieve_req(struct arm_smccc_res *res, u32 len)
+{
+	arm_smccc_1_1_smc(FFA_FN64_MEM_RETRIEVE_REQ,
+			  len, len,
+			  0, 0, 0, 0, 0,
+			  res);
+}
+
 static void do_ffa_rxtx_map(struct arm_smccc_res *res,
 			    struct kvm_cpu_context *ctxt)
 {

@@ -375,6 +392,65 @@ static void do_ffa_mem_share(struct arm_smccc_res *res,
 	return;
 }
 
+static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
+			       struct kvm_cpu_context *ctxt)
+{
+	DECLARE_REG(u32, handle_lo, ctxt, 1);
+	DECLARE_REG(u32, handle_hi, ctxt, 2);
+	DECLARE_REG(u32, flags, ctxt, 3);
+	struct ffa_composite_mem_region *reg;
+	struct ffa_mem_region *buf;
+	int ret = 0;
+	u32 offset;
+	u64 handle;
+
+	handle = PACK_HANDLE(handle_lo, handle_hi);
+
+	hyp_spin_lock(&host_buffers.lock);
+
+	buf = hyp_buffers.tx;
+	*buf = (struct ffa_mem_region) {
+		.sender_id	= HOST_FFA_ID,
+		.handle		= handle,
+	};
+
+	spmd_retrieve_req(res, sizeof(*buf));
+	buf = hyp_buffers.rx;
+	if (res->a0 != FFA_MEM_RETRIEVE_RESP)
+		goto out_unlock;
+
+	/* Check for fragmentation */
+	if (res->a1 != res->a2) {
+		ret = FFA_RET_ABORTED;
+		goto out_unlock;
+	}
+
+	offset = buf->ep_mem_access[0].composite_off;
+	/*
+	 * We can trust the SPMD to get this right, but let's at least
+	 * check that we end up with something that doesn't look _completely_
+	 * bogus.
+	 */
+	if (WARN_ON(offset > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) {
+		ret = FFA_RET_ABORTED;
+		goto out_unlock;
+	}
+
+	reg = (void *)buf + offset;
+	spmd_mem_reclaim(res, handle_lo, handle_hi, flags);
+	if (res->a0 != FFA_SUCCESS)
+		goto out_unlock;
+
+	/* If the SPMD was happy, then we should be too. */
+	WARN_ON(ffa_host_unshare_ranges(reg->constituents,
+					reg->addr_range_cnt));
+out_unlock:
+	hyp_spin_unlock(&host_buffers.lock);
+
+	if (ret)
+		ffa_to_smccc_res(res, ret);
+}
+
 /*
  * Is a given FFA function supported, either by forwarding on directly
  * or by handling at EL2?

@@ -428,6 +504,9 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 	case FFA_FN64_MEM_SHARE:
 		do_ffa_mem_share(&res, host_ctxt);
 		goto out_handled;
+	case FFA_MEM_RECLAIM:
+		do_ffa_mem_reclaim(&res, host_ctxt);
+		goto out_handled;
 	}
 
 	if (ffa_call_supported(func_id))

index b23e3869ce63..45a2726d73ff 100644
@@ -116,10 +116,10 @@ static int spmd_unmap_ffa_buffers(void)
 	return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
 }
 
-static void spmd_mem_share(struct arm_smccc_res *res, u32 len, u32 fraglen)
+static void spmd_mem_xfer(struct arm_smccc_res *res, u64 func_id, u32 len,
+			  u32 fraglen)
 {
-	arm_smccc_1_1_smc(FFA_FN64_MEM_SHARE,
-			  len, fraglen,
+	arm_smccc_1_1_smc(func_id, len, fraglen,
 			  0, 0, 0, 0, 0,
 			  res);
 }

@@ -317,8 +317,9 @@ static int ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
 	return ret;
 }
 
-static void do_ffa_mem_share(struct arm_smccc_res *res,
-			     struct kvm_cpu_context *ctxt)
+static __always_inline void do_ffa_mem_xfer(const u64 func_id,
+					    struct arm_smccc_res *res,
+					    struct kvm_cpu_context *ctxt)
 {
 	DECLARE_REG(u32, len, ctxt, 1);
 	DECLARE_REG(u32, fraglen, ctxt, 2);

@@ -329,6 +330,9 @@ static void do_ffa_mem_share(struct arm_smccc_res *res,
 	int ret = 0;
 	u32 offset;
 
+	BUILD_BUG_ON(func_id != FFA_FN64_MEM_SHARE &&
+		     func_id != FFA_FN64_MEM_LEND);
+
 	if (addr_mbz || npages_mbz || fraglen > len ||
 	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
 		ret = FFA_RET_INVALID_PARAMETERS;

@@ -378,7 +382,7 @@ static void do_ffa_mem_share(struct arm_smccc_res *res,
 	if (ret)
 		goto out_unlock;
 
-	spmd_mem_share(res, len, fraglen);
+	spmd_mem_xfer(res, func_id, len, fraglen);
 	if (res->a0 != FFA_SUCCESS) {
 		WARN_ON(ffa_host_unshare_ranges(reg->constituents,
 						reg->addr_range_cnt));

@@ -502,11 +506,15 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 		goto out_handled;
 	case FFA_MEM_SHARE:
 	case FFA_FN64_MEM_SHARE:
-		do_ffa_mem_share(&res, host_ctxt);
+		do_ffa_mem_xfer(FFA_FN64_MEM_SHARE, &res, host_ctxt);
 		goto out_handled;
 	case FFA_MEM_RECLAIM:
 		do_ffa_mem_reclaim(&res, host_ctxt);
 		goto out_handled;
+	case FFA_MEM_LEND:
+	case FFA_FN64_MEM_LEND:
+		do_ffa_mem_xfer(FFA_FN64_MEM_LEND, &res, host_ctxt);
+		goto out_handled;
 	}
 
 	if (ffa_call_supported(func_id))

index 45a2726d73ff..aa8bfc97a164 100644
@@ -64,15 +64,21 @@ static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 	};
 }
 
-static void ffa_to_smccc_res(struct arm_smccc_res *res, int ret)
+static void ffa_to_smccc_res_prop(struct arm_smccc_res *res, int ret, u64 prop)
 {
 	if (ret == FFA_RET_SUCCESS) {
-		*res = (struct arm_smccc_res) { .a0 = FFA_SUCCESS };
+		*res = (struct arm_smccc_res) { .a0 = FFA_SUCCESS,
+						.a2 = prop };
 	} else {
 		ffa_to_smccc_error(res, ret);
 	}
 }
 
+static void ffa_to_smccc_res(struct arm_smccc_res *res, int ret)
+{
+	ffa_to_smccc_res_prop(res, ret, 0);
+}
+
 static void ffa_set_retval(struct kvm_cpu_context *ctxt,
 			   struct arm_smccc_res *res)
 {

@@ -480,14 +486,41 @@ static bool ffa_call_supported(u64 func_id)
 	case FFA_RXTX_MAP:
 	case FFA_MEM_DONATE:
 	case FFA_MEM_RETRIEVE_REQ:
-	/* Don't advertise any features just yet */
-	case FFA_FEATURES:
 		return false;
 	}
 
 	return true;
 }
 
+static bool do_ffa_features(struct arm_smccc_res *res,
+			    struct kvm_cpu_context *ctxt)
+{
+	DECLARE_REG(u32, id, ctxt, 1);
+	u64 prop = 0;
+	int ret = 0;
+
+	if (!ffa_call_supported(id)) {
+		ret = FFA_RET_NOT_SUPPORTED;
+		goto out_handled;
+	}
+
+	switch (id) {
+	case FFA_MEM_SHARE:
+	case FFA_FN64_MEM_SHARE:
+	case FFA_MEM_LEND:
+	case FFA_FN64_MEM_LEND:
+		ret = FFA_RET_SUCCESS;
+		prop = 0; /* No support for dynamic buffers */
+		goto out_handled;
+	default:
+		return false;
+	}
+
+out_handled:
+	ffa_to_smccc_res_prop(res, ret, prop);
+	return true;
+}
+
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(u64, func_id, host_ctxt, 0);

@@ -497,6 +530,10 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 		return false;
 
 	switch (func_id) {
+	case FFA_FEATURES:
+		if (!do_ffa_features(&res, host_ctxt))
+			return false;
+		goto out_handled;
 	/* Memory management */
 	case FFA_FN64_RXTX_MAP:
 		do_ffa_rxtx_map(&res, host_ctxt);

index 2b495ec59deb..e46250a02017 100644
@@ -6,7 +6,9 @@
 #ifndef __ARM64_KVM_PKVM_H__
 #define __ARM64_KVM_PKVM_H__
 
+#include <linux/arm_ffa.h>
 #include <linux/memblock.h>
+#include <linux/scatterlist.h>
 #include <asm/kvm_pgtable.h>
 
 /* Maximum number of VMs that can co-exist under pKVM. */

@@ -110,8 +112,19 @@ static inline unsigned long host_s2_pgtable_pages(void)
 
 static inline unsigned long hyp_ffa_proxy_pages(void)
 {
-	/* A page each for the hypervisor's RX and TX mailboxes. */
-	return 2 * KVM_FFA_MBOX_NR_PAGES;
+	size_t desc_max;
+
+	/*
+	 * The hypervisor FFA proxy needs enough memory to buffer a fragmented
+	 * descriptor returned from EL3 in response to a RETRIEVE_REQ call.
+	 */
+	desc_max = sizeof(struct ffa_mem_region) +
+		   sizeof(struct ffa_mem_region_attributes) +
+		   sizeof(struct ffa_composite_mem_region) +
+		   SG_MAX_SEGMENTS * sizeof(struct ffa_mem_region_addr_range);
+
+	/* Plus a page each for the hypervisor's RX and TX mailboxes. */
+	return (2 * KVM_FFA_MBOX_NR_PAGES) + DIV_ROUND_UP(desc_max, PAGE_SIZE);
 }
 
 #endif	/* __ARM64_KVM_PKVM_H__ */

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