[PATCH v3 17/17] KVM: arm64: Alloc simple_buffer_page using pKVM hyp allocator

[Vincent Donnefort <vdonnefort@google.com>]

In protected mode, transition the allocation of the simple_ring_buffer
structures from the host to the hypervisor using the new pKVM heap
allocator.

Previously, the host allocated and donated a contiguous backing memory
for these structures. In pKVM the hypervisor can now allocate them
dynamically.

Use the pkvm_call_hyp_req() wrapper in the host to invoke
__tracing_load, which automatically handles any top-up requests if the
hypervisor runs out of heap memory during allocation.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 01e7ffc489f5..a5b740d152be 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -745,7 +745,7 @@ static void handle___tracing_load(struct kvm_cpu_context *host_ctxt)
 	DECLARE_REG(unsigned long, desc_hva, host_ctxt, 1);
 	DECLARE_REG(size_t, desc_size, host_ctxt, 2);
 
-	cpu_reg(host_ctxt, 1) = __tracing_load(desc_hva, desc_size);
+	errno_to_smccc(__tracing_load(desc_hva, desc_size), host_ctxt);
 }
 
 static void handle___tracing_unload(struct kvm_cpu_context *host_ctxt)
diff --git a/arch/arm64/kvm/hyp/nvhe/trace.c b/arch/arm64/kvm/hyp/nvhe/trace.c
index 96afa3d6de2f..5ff19d210508 100644
--- a/arch/arm64/kvm/hyp/nvhe/trace.c
+++ b/arch/arm64/kvm/hyp/nvhe/trace.c
@@ -4,6 +4,7 @@
  * Author: Vincent Donnefort <vdonnefort@google.com>
  */
 
+#include <nvhe/alloc.h>
 #include <nvhe/clock.h>
 #include <nvhe/mem_protect.h>
 #include <nvhe/mm.h>
@@ -62,18 +63,34 @@ static void __release_host_mem(void *start, u64 size)
 	WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(start), size >> PAGE_SHIFT));
 }
 
-static int hyp_trace_buffer_load_bpage_backing(struct hyp_trace_buffer *trace_buffer,
-					       struct hyp_trace_desc *desc)
+static int hyp_trace_buffer_alloc_bpages(struct hyp_trace_buffer *trace_buffer,
+					 struct hyp_trace_desc *desc)
 {
-	void *start = (void *)kern_hyp_va(desc->bpages_backing_start);
-	size_t size = desc->bpages_backing_size;
+	void *start;
+	size_t size;
 	int ret;
 
-	ret = __admit_host_mem(start, size);
-	if (ret)
-		return ret;
+	if (is_protected_kvm_enabled()) {
+		struct ring_buffer_desc *rb_desc;
+		int cpu;
 
-	memset(start, 0, size);
+		size = 0;
+		for_each_ring_buffer_desc(rb_desc, cpu, &desc->trace_buffer_desc)
+			size += rb_desc->nr_page_va * sizeof(struct simple_buffer_page);
+
+		start = hyp_alloc(size);
+		if (!start)
+			return hyp_alloc_errno();
+	} else {
+		start = (void *)kern_hyp_va(desc->bpages_backing_start);
+		size = desc->bpages_backing_size;
+
+		ret = __admit_host_mem(start, size);
+		if (ret)
+			return ret;
+
+		memset(start, 0, size);
+	}
 
 	trace_buffer->bpages_backing_start = start;
 	trace_buffer->bpages_backing_size = size;
@@ -81,7 +98,7 @@ static int hyp_trace_buffer_load_bpage_backing(struct hyp_trace_buffer *trace_bu
 	return 0;
 }
 
-static void hyp_trace_buffer_unload_bpage_backing(struct hyp_trace_buffer *trace_buffer)
+static void hyp_trace_buffer_free_bpages(struct hyp_trace_buffer *trace_buffer)
 {
 	void *start = trace_buffer->bpages_backing_start;
 	size_t size = trace_buffer->bpages_backing_size;
@@ -89,9 +106,12 @@ static void hyp_trace_buffer_unload_bpage_backing(struct hyp_trace_buffer *trace
 	if (!size)
 		return;
 
-	memset(start, 0, size);
-
-	__release_host_mem(start, size);
+	if (is_protected_kvm_enabled()) {
+		hyp_free(start);
+	} else {
+		memset(start, 0, size);
+		__release_host_mem(start, size);
+	}
 
 	trace_buffer->bpages_backing_start = 0;
 	trace_buffer->bpages_backing_size = 0;
@@ -128,7 +148,7 @@ static void hyp_trace_buffer_unload(struct hyp_trace_buffer *trace_buffer)
 		simple_ring_buffer_unload_mm(per_cpu_ptr(trace_buffer->simple_rbs, cpu),
 					     __unpin_shared_page);
 
-	hyp_trace_buffer_unload_bpage_backing(trace_buffer);
+	hyp_trace_buffer_free_bpages(trace_buffer);
 }
 
 static int hyp_trace_buffer_load(struct hyp_trace_buffer *trace_buffer,
@@ -143,7 +163,7 @@ static int hyp_trace_buffer_load(struct hyp_trace_buffer *trace_buffer,
 	if (hyp_trace_buffer_loaded(trace_buffer))
 		return -EINVAL;
 
-	ret = hyp_trace_buffer_load_bpage_backing(trace_buffer, desc);
+	ret = hyp_trace_buffer_alloc_bpages(trace_buffer, desc);
 	if (ret)
 		return ret;
 
@@ -168,18 +188,16 @@ static bool hyp_trace_desc_is_valid(struct hyp_trace_desc *desc, size_t desc_siz
 {
 	struct ring_buffer_desc *rb_desc;
 	unsigned int cpu;
-	size_t nr_bpages;
 	void *desc_end;
 
 	if (!is_protected_kvm_enabled())
 		return true;
 
 	/*
-	 * Both desc_size and bpages_backing_size are untrusted host-provided
-	 * values. We rely on __pkvm_host_donate_hyp() to enforce their validity.
+	 * desc_size is an untrusted host-provided value. We rely on
+	 * __pkvm_host_donate_hyp() to enforce its validity.
 	 */
 	desc_end = (void *)desc + desc_size;
-	nr_bpages = desc->bpages_backing_size / sizeof(struct simple_buffer_page);
 
 	if (desc->trace_buffer_desc.nr_cpus != hyp_nr_cpus)
 		return false;
@@ -197,17 +215,8 @@ static bool hyp_trace_desc_is_valid(struct hyp_trace_desc *desc, size_t desc_siz
 		if ((void *)rb_desc + struct_size(rb_desc, page_va, rb_desc->nr_page_va) > desc_end)
 			return false;
 
-		/* Overflow bpages backing memory? */
-		if (nr_bpages < rb_desc->nr_page_va)
-			return false;
-
-		if (cpu >= hyp_nr_cpus)
-			return false;
-
 		if (cpu != rb_desc->cpu)
 			return false;
-
-		nr_bpages -= rb_desc->nr_page_va;
 	}
 
 	return true;
diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
index 2411b4c32932..859a926c815f 100644
--- a/arch/arm64/kvm/hyp_trace.c
+++ b/arch/arm64/kvm/hyp_trace.c
@@ -13,6 +13,7 @@
 #include <asm/kvm_host.h>
 #include <asm/kvm_hyptrace.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_pkvm.h>
 
 #include "hyp_trace.h"
 
@@ -157,10 +158,17 @@ static void __unshare_page(unsigned long va)
 
 static int hyp_trace_buffer_alloc_bpages_backing(struct hyp_trace_buffer *trace_buffer, size_t size)
 {
-	int nr_bpages = (PAGE_ALIGN(size) / PAGE_SIZE) + 1;
 	size_t backing_size;
+	int nr_bpages;
 	void *start;
 
+	if (is_protected_kvm_enabled()) {
+		trace_buffer->desc->bpages_backing_start = 0;
+		trace_buffer->desc->bpages_backing_size = 0;
+		return 0;
+	}
+
+	nr_bpages = (PAGE_ALIGN(size) / PAGE_SIZE) + 1;
 	backing_size = PAGE_ALIGN(sizeof(struct simple_buffer_page) * nr_bpages *
 				  num_possible_cpus());
 
@@ -176,6 +184,9 @@ static int hyp_trace_buffer_alloc_bpages_backing(struct hyp_trace_buffer *trace_
 
 static void hyp_trace_buffer_free_bpages_backing(struct hyp_trace_buffer *trace_buffer)
 {
+	if (!trace_buffer->desc->bpages_backing_start)
+		return;
+
 	free_pages_exact((void *)trace_buffer->desc->bpages_backing_start,
 			 trace_buffer->desc->bpages_backing_size);
 }
@@ -264,7 +275,7 @@ static struct trace_buffer_desc *hyp_trace_load(unsigned long size, void *priv)
 	if (ret)
 		goto err_free_buffer;
 
-	ret = kvm_call_hyp_nvhe(__tracing_load, (unsigned long)desc, desc_size);
+	ret = pkvm_call_hyp_req(__tracing_load, (unsigned long)desc, desc_size);
 	if (ret)
 		goto err_unload_pages;
 
-- 
2.55.0.229.g6434b31f56-goog