KVM: arm64: Handle FFA_MEM_SHARE calls from the host

Intercept FFA_MEM_SHARE/FFA_FN64_MEM_SHARE calls from the host and
transition the host stage-2 page-table entries from the OWNED state to
the SHARED_OWNED state prior to forwarding the call onto EL3.
Co-developed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230523101828.7328-7-will@kernel.orgSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/kvm/hyp/nvhe/ffa.c

@@ -116,6 +116,14 @@ static int ffa_unmap_hyp_buffers(void)
 	return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
 }
 
+static void ffa_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)
 {
@@ -228,6 +236,149 @@ 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;
+
+	ffa_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?
@@ -290,6 +441,10 @@ 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))