[PATCH v2 06/14] hv: vmbus: cover all shared-page policy combinations
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HOTtoday
From: Emerson Busson <hidden>
Date: 2026-10-07 19:08:38
Also in:
linux-hyperv, lkml
Subsystem:
hyper-v/azure core and drivers, the rest · Maintainers:
"K. Y. Srinivasan", Haiyang Zhang, Wei Liu, Dexuan Cui, Long Li, Linus Torvalds
Name the shared-page selection and enumerate all eight combinations of Hyper-V isolation, independent guest-memory encryption and channel confidentiality. Either platform visibility signal selects shared backing; the confidential-channel override keeps private backing. These are decision tests, not confidential hardware qualification. Signed-off-by: Emerson Busson <redacted> --- drivers/hv/channel.c | 16 ++++++++++++++-- drivers/hv/hyperv_vmbus.h | 2 ++ drivers/hv/vmbus_buffer_test.c | 29 +++++++++++++++++++++++++++++ 3 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 0c025a12808a..8ed155f2669f 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c@@ -45,6 +45,13 @@ int vmbus_buffer_round_size(u32 size, u32 *rounded_size) return 0; } +bool +vmbus_needs_shared_pages(bool hv_isolation, bool guest_mem_encrypted, + bool confidential) +{ + return !confidential && (hv_isolation || guest_mem_encrypted); +} + unsigned int vmbus_buffer_order(unsigned long remaining, unsigned int max_order) {
@@ -837,6 +844,8 @@ static void *__vmbus_alloc_buffer(struct vmbus_channel *channel, unsigned long nr_pages; unsigned long remaining; unsigned long page_idx = 0; + bool hv_isolation; + bool guest_mem_encrypted; struct page **chunks = NULL; struct page **pages = NULL; unsigned int order = MAX_PAGE_ORDER;
@@ -853,9 +862,12 @@ static void *__vmbus_alloc_buffer(struct vmbus_channel *channel, nr_pages = rounded_size >> PAGE_SHIFT; remaining = nr_pages; + hv_isolation = hv_is_isolation_supported(); + guest_mem_encrypted = cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT); + /* If the buffer does not need to be decrypted, just use vzalloc() */ - if ((!hv_is_isolation_supported() && - !cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) || confidential) + if (!vmbus_needs_shared_pages(hv_isolation, guest_mem_encrypted, + confidential)) return vzalloc(rounded_size); /* Worst case: every chunk is a single page. */
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index e08c472041d5..06094000f2f1 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h@@ -557,6 +557,8 @@ int hv_remove_ring_sysfs(struct vmbus_channel *channel); * These are shared with vmbus_buffer_test.c, which is built into the * hv_vmbus object alongside channel.c. They stay unexported. */ +bool vmbus_needs_shared_pages(bool hv_isolation, bool guest_mem_encrypted, + bool confidential); int vmbus_buffer_round_size(u32 size, u32 *rounded_size); unsigned int vmbus_buffer_order(unsigned long remaining, unsigned int max_order);
diff --git a/drivers/hv/vmbus_buffer_test.c b/drivers/hv/vmbus_buffer_test.c
index 60fc526af1af..9b401ef2ceea 100644
--- a/drivers/hv/vmbus_buffer_test.c
+++ b/drivers/hv/vmbus_buffer_test.c@@ -38,6 +38,34 @@ static void vmbus_buffer_size_overflow_test(struct kunit *test) (u32)(U32_MAX - PAGE_SIZE + 1)); } +static void vmbus_buffer_private_shared_selection_test(struct kunit *test) +{ + static const struct { + bool isolation; + bool encrypted; + bool confidential; + bool shared; + } cases[] = { + { false, false, false, false }, + { false, false, true, false }, + { false, true, false, true }, + { false, true, true, false }, + { true, false, false, true }, + { true, false, true, false }, + { true, true, false, true }, + { true, true, true, false }, + }; + unsigned int i; + + /* Either platform signal requires visibility; confidential stays private. */ + for (i = 0; i < ARRAY_SIZE(cases); i++) + KUNIT_EXPECT_EQ(test, + vmbus_needs_shared_pages(cases[i].isolation, + cases[i].encrypted, + cases[i].confidential), + cases[i].shared); +} + static void vmbus_ring_fallback_order_zero_test(struct kunit *test) { unsigned int order;
@@ -317,6 +345,7 @@ static void vmbus_buffer_order_zero_allocation_test(struct kunit *test) static struct kunit_case vmbus_buffer_test_cases[] = { KUNIT_CASE(vmbus_buffer_size_rounding_test), KUNIT_CASE(vmbus_buffer_size_overflow_test), + KUNIT_CASE(vmbus_buffer_private_shared_selection_test), KUNIT_CASE(vmbus_ring_fallback_order_zero_test), KUNIT_CASE(vmbus_buffer_failed_teardown_leaks_test), KUNIT_CASE(vmbus_buffer_partial_allocation_cleanup_test),
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2.43.0