---
Changes since v2:
- Checkpatch format fix
Changes since RFC:
- Handle direct-map restoration failures without returning unmapped
pages to the allocator.
- Move freeing of withdrawn pages into the restoration helper.
---
drivers/hv/hv_proc.c | 77 +++++++++++++++++++++++++++++++++-
drivers/hv/mshv_root_hv_call.c | 4 +-
include/asm-generic/mshyperv.h | 4 ++
3 files changed, 81 insertions(+), 4 deletions(-)
diff --git a/drivers/hv/hv_proc.c b/drivers/hv/hv_proc.c
index 57b2c64197cb..2a392b45205d 100644
--- a/drivers/hv/hv_proc.c
+++ b/drivers/hv/hv_proc.c
@@ -7,7 +7,9 @@
#include <linux/cpuhotplug.h>
#include <linux/minmax.h>
#include <linux/export.h>
+#include <linux/set_memory.h>
#include <asm/mshyperv.h>
+#include <asm/tlbflush.h>
/*
* See struct hv_deposit_memory. The first u64 is partition ID, the rest
@@ -15,6 +17,35 @@
*/
#define HV_DEPOSIT_MAX (HV_HYP_PAGE_SIZE / sizeof(u64) - 1)
+/*
+ * Add or remove a set of physically contiguous page runs from the kernel
+ * direct map. Once a page has been deposited the hypervisor owns it and
+ * revokes root partition access to it.
+ */
+static int hv_deposit_update_direct_map(struct page **pages, int *counts,
+ int num_allocations, bool valid)
+{
+ int i, err, ret = 0;
+
+ for (i = 0; i < num_allocations; ++i) {
+ err = set_direct_map_valid_noflush(pages[i], counts[i], valid);
+ if (err && !ret)
+ ret = err;
+ }
+
+ if (valid)
+ return ret;
+
+ for (i = 0; i < num_allocations; ++i) {
+ unsigned long addr = (unsigned long)page_address(pages[i]);
+ unsigned long size = (unsigned long)counts[i] << PAGE_SHIFT;
+
+ flush_tlb_kernel_range(addr, addr + size);
+ }
+
+ return ret;
+}
+
/* Deposits exact number of pages. Must be called with interrupts enabled. */
int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages)
{
@@ -72,6 +103,10 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32
num_pages)
}
num_allocations = i;
+ ret = hv_deposit_update_direct_map(pages, counts, num_allocations, false);
+ if (ret)
+ goto err_restore_direct_map;
+
local_irq_save(flags);
input_page = *this_cpu_ptr(hyperv_pcpu_input_arg);
@@ -90,12 +125,23 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32
num_pages)
if (!hv_result_success(status)) {
hv_status_err(status, "\n");
ret = hv_result_to_errno(status);
- goto err_free_allocations;
+ goto err_restore_direct_map;
}
ret = 0;
goto free_buf;
+err_restore_direct_map:
+ /*
+ * We don't want to return pages to the allocator if weren't able to
+ * mark them valid in the direct map.
+ */
+ if (hv_deposit_update_direct_map(pages, counts, num_allocations, true))
{
+ WARN(1, "leaking %d page block(s) that could not be set to
valid\n",
+ num_allocations);
+ goto free_buf;
+ }
+
err_free_allocations:
for (i = 0; i < num_allocations; ++i) {
base_pfn = page_to_pfn(pages[i]);
@@ -110,6 +156,35 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32
num_pages)
}
EXPORT_SYMBOL_GPL(hv_call_deposit_pages);
+/*
+ * Put withdrawn pages back in the direct map. Counterpart to the direct map
+ * removal done by hv_call_deposit_pages().
+ */
+void hv_restore_withdrawn_pages(const u64 *pfns, int count)
+{
+ int i, ret = 0;
+ struct page *page;
+
+ for (i = 0; i < count; ++i) {
+ page = pfn_to_page(pfns[i]);
+ ret = set_direct_map_valid_noflush(page, 1, true);
+ /*
+ * HV_DEPOSIT_MAX is capped at 511, so a deposit range cannot
cover
+ * a 2MiB page, so deposited pages are of 4k granularity and
cannot
+ * be collapses into a 2MiB page, which would require an
allocation
+ * and can potentially fail.
+ *
+ * Should it fail anyway we leak the page, if we would hand it
+ * back to the allocator we would introduce faults into random
other
+ * parts.
+ */
+ if (WARN_ON_ONCE(ret))
+ continue;
+ __free_page(page);
+ }
+}
+EXPORT_SYMBOL_GPL(hv_restore_withdrawn_pages);
+
int hv_deposit_memory_node(int node, u64 partition_id,
u64 hv_status)
{
diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
index cb55d4d4be2e..150a0c63ebc8 100644
--- a/drivers/hv/mshv_root_hv_call.c
+++ b/drivers/hv/mshv_root_hv_call.c
@@ -46,7 +46,6 @@ int hv_call_withdraw_memory(u64 count, int node, u64
partition_id)
struct page *page;
u16 completed;
u64 status, withdrawn = 0;
- int i;
unsigned long flags;
page = alloc_page(GFP_KERNEL);
@@ -69,8 +68,7 @@ int hv_call_withdraw_memory(u64 count, int node, u64
partition_id)
completed = hv_repcomp(status);
- for (i = 0; i < completed; i++)
- __free_page(pfn_to_page(output_page->gpa_page_list[i]));
+ hv_restore_withdrawn_pages(output_page->gpa_page_list,
completed);
if (!hv_result_success(status)) {
if (hv_result(status) == HV_STATUS_NO_RESOURCES)
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index bf601d67cecb..397c8ec0ce9a 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -346,6 +346,7 @@ static inline bool hv_parent_partition(void)
bool hv_result_needs_memory(u64 status);
int hv_deposit_memory_node(int node, u64 partition_id, u64 status);
int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
+void hv_restore_withdrawn_pages(const u64 *pfns, int count);
int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
int hv_call_notify_all_processors_started(void);
bool hv_lp_exists(u32 lp_index);
@@ -364,6 +365,9 @@ static inline int hv_call_deposit_pages(int node, u64
partition_id, u32 num_page
{
return -EOPNOTSUPP;
}
+
+static inline void hv_restore_withdrawn_pages(const u64 *pfns, int count) { }
+
static inline int hv_call_add_logical_proc(int node, u32 lp_index, u32
acpi_id)
{
return -EOPNOTSUPP;
