[RFC PATCH 07/18] virt/mshv: withdraw memory hypercall

[Nuno Das Neves <nunodasneves@linux.microsoft.com>]

Withdraw the memory from a finalized partition and free the pages.
The partition is now cleaned up correctly when the fd is released.

Co-developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
---
 include/asm-generic/hyperv-tlfs.h | 10 ++++++
 virt/mshv/mshv_main.c             | 54 ++++++++++++++++++++++++++++++-
 2 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index ab6ae6c164f5..2a49503b7396 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -148,6 +148,7 @@ struct ms_hyperv_tsc_page {
 #define HVCALL_DELETE_PARTITION			0x0043
 #define HVCALL_GET_PARTITION_ID			0x0046
 #define HVCALL_DEPOSIT_MEMORY			0x0048
+#define HVCALL_WITHDRAW_MEMORY			0x0049
 #define HVCALL_CREATE_VP			0x004e
 #define HVCALL_GET_VP_REGISTERS			0x0050
 #define HVCALL_SET_VP_REGISTERS			0x0051
@@ -472,6 +473,15 @@ union hv_proximity_domain_info {
 	u64 as_uint64;
 };
 
+struct hv_withdraw_memory_in {
+	u64 partition_id;
+	union hv_proximity_domain_info proximity_domain_info;
+};
+
+struct hv_withdraw_memory_out {
+	u64 gpa_page_list[0];
+};
+
 struct hv_lp_startup_status {
 	u64 hv_status;
 	u64 substatus1;
diff --git a/virt/mshv/mshv_main.c b/virt/mshv/mshv_main.c
index c4130a6508e5..162a1bb42a4a 100644
--- a/virt/mshv/mshv_main.c
+++ b/virt/mshv/mshv_main.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/anon_inodes.h>
+#include <linux/mm.h>
 #include <linux/mshv.h>
 #include <asm/mshyperv.h>
 
@@ -57,8 +58,58 @@ static struct miscdevice mshv_dev = {
 	.mode = 600,
 };
 
+#define HV_WITHDRAW_BATCH_SIZE	(PAGE_SIZE / sizeof(u64))
 #define HV_INIT_PARTITION_DEPOSIT_PAGES 208
 
+static int
+hv_call_withdraw_memory(u64 count, int node, u64 partition_id)
+{
+	struct hv_withdraw_memory_in *input_page;
+	struct hv_withdraw_memory_out *output_page;
+	u16 completed;
+	u64 hypercall_status;
+	unsigned long remaining = count;
+	int status;
+	int i;
+	unsigned long flags;
+
+	while (remaining) {
+		local_irq_save(flags);
+
+		input_page = (struct hv_withdraw_memory_in *)(*this_cpu_ptr(
+			hyperv_pcpu_input_arg));
+		output_page = (struct hv_withdraw_memory_out *)(*this_cpu_ptr(
+			hyperv_pcpu_output_arg));
+
+		input_page->partition_id = partition_id;
+		input_page->proximity_domain_info.as_uint64 = 0;
+		hypercall_status = hv_do_rep_hypercall(
+			HVCALL_WITHDRAW_MEMORY,
+			min(remaining, HV_WITHDRAW_BATCH_SIZE), 0, input_page,
+			output_page);
+
+		completed = (hypercall_status & HV_HYPERCALL_REP_COMP_MASK) >>
+			    HV_HYPERCALL_REP_COMP_OFFSET;
+
+		for (i = 0; i < completed; i++)
+			__free_page(pfn_to_page(output_page->gpa_page_list[i]));
+
+		local_irq_restore(flags);
+
+		status = hypercall_status & HV_HYPERCALL_RESULT_MASK;
+		if (status != HV_STATUS_SUCCESS) {
+			if (status != HV_STATUS_NO_RESOURCES)
+				pr_err("%s: %s\n", __func__,
+				       hv_status_to_string(status));
+			break;
+		}
+
+		remaining -= completed;
+	}
+
+	return -hv_status_to_errno(status);
+}
+
 static int
 hv_call_create_partition(
 		u64 flags,
@@ -230,7 +281,8 @@ destroy_partition(struct mshv_partition *partition)
 
 	/* Deallocates and unmaps everything including vcpus, GPA mappings etc */
 	hv_call_finalize_partition(partition->id);
-	/* TODO: Withdraw and free all pages we deposited */
+	/* Withdraw and free all pages we deposited */
+	hv_call_withdraw_memory(U64_MAX, NUMA_NO_NODE, partition->id);
 
 	hv_call_delete_partition(partition->id);
 
-- 
2.25.1