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Subject[PATCH] x86/Hyper-V: Support for free page reporting
Date
Linux has support for free page reporting now (36e66c554b5c) for
virtualized environment. On Hyper-V when virtually backed VMs are
configured, Hyper-V will advertise cold memory discard capability,
when supported. This patch adds the support to hook into the free
page reporting infrastructure and leverage the Hyper-V cold memory
discard hint hypercall to report/free these pages back to the host.

Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
---
First patch mail bounced backed. Sending it again with the email
addresses fixed.
---
arch/x86/hyperv/hv_init.c | 24 ++++++++
arch/x86/kernel/cpu/mshyperv.c | 6 +-
drivers/hv/hv_balloon.c | 93 +++++++++++++++++++++++++++++++
include/asm-generic/hyperv-tlfs.h | 29 ++++++++++
include/asm-generic/mshyperv.h | 2 +
5 files changed, 152 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 624f5d9b0f79..925e2f7eb82c 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -506,3 +506,27 @@ bool hv_is_hibernation_supported(void)
return acpi_sleep_state_supported(ACPI_STATE_S4);
}
EXPORT_SYMBOL_GPL(hv_is_hibernation_supported);
+
+u64 hv_query_ext_cap(void)
+{
+ u64 *cap;
+ unsigned long flags;
+ u64 ext_cap = 0;
+
+ /*
+ * Querying extended capabilities is an extended hypercall. Check if the
+ * partition supports extended hypercall, first.
+ */
+ if (!(ms_hyperv.b_features & HV_ENABLE_EXTENDED_HYPERCALLS))
+ return 0;
+
+ local_irq_save(flags);
+ cap = *(u64 **)this_cpu_ptr(hyperv_pcpu_input_arg);
+ if (hv_do_hypercall(HV_EXT_CALL_QUERY_CAPABILITIES, NULL, cap) ==
+ HV_STATUS_SUCCESS)
+ ext_cap = *cap;
+
+ local_irq_restore(flags);
+ return ext_cap;
+}
+EXPORT_SYMBOL_GPL(hv_query_ext_cap);
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index ebf34c7bc8bc..2de3f692c8bf 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -224,11 +224,13 @@ static void __init ms_hyperv_init_platform(void)
* Extract the features and hints
*/
ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
+ ms_hyperv.b_features = cpuid_ebx(HYPERV_CPUID_FEATURES);
ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
ms_hyperv.hints = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);

- pr_info("Hyper-V: features 0x%x, hints 0x%x, misc 0x%x\n",
- ms_hyperv.features, ms_hyperv.hints, ms_hyperv.misc_features);
+ pr_info("Hyper-V: features 0x%x, additional features: 0x%x, hints 0x%x, misc 0x%x\n",
+ ms_hyperv.features, ms_hyperv.b_features, ms_hyperv.hints,
+ ms_hyperv.misc_features);

ms_hyperv.max_vp_index = cpuid_eax(HYPERV_CPUID_IMPLEMENT_LIMITS);
ms_hyperv.max_lp_index = cpuid_ebx(HYPERV_CPUID_IMPLEMENT_LIMITS);
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 32e3bc0aa665..77be31094556 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -21,6 +21,7 @@
#include <linux/memory.h>
#include <linux/notifier.h>
#include <linux/percpu_counter.h>
+#include <linux/page_reporting.h>

#include <linux/hyperv.h>
#include <asm/hyperv-tlfs.h>
@@ -563,6 +564,10 @@ struct hv_dynmem_device {
* The negotiated version agreed by host.
*/
__u32 version;
+
+#ifdef CONFIG_PAGE_REPORTING
+ struct page_reporting_dev_info pr_dev_info;
+#endif
};

static struct hv_dynmem_device dm_device;
@@ -1565,6 +1570,83 @@ static void balloon_onchannelcallback(void *context)

}

+#ifdef CONFIG_PAGE_REPORTING
+static int hv_free_page_report(struct page_reporting_dev_info *pr_dev_info,
+ struct scatterlist *sgl, unsigned int nents)
+{
+ unsigned long flags;
+ struct hv_memory_hint *hint;
+ int i;
+ u64 status;
+ struct scatterlist *sg;
+
+ WARN_ON(nents > HV_MAX_GPA_PAGE_RANGES);
+ local_irq_save(flags);
+ hint = *(struct hv_memory_hint **)this_cpu_ptr(hyperv_pcpu_input_arg);
+ if (!hint) {
+ local_irq_restore(flags);
+ return -ENOSPC;
+ }
+
+ hint->type = HV_EXT_MEMORY_HEAT_HINT_TYPE_COLD_DISCARD;
+ hint->reserved = 0;
+ for (i = 0, sg = sgl; sg; sg = sg_next(sg), i++) {
+ int order;
+ union hv_gpa_page_range *range;
+
+ order = get_order(sg->length);
+ range = &hint->ranges[i];
+ range->address_space = 0;
+ range->page.largepage = 1;
+ range->page.additional_pages = (1ull << (order - 9)) - 1;
+ range->base_large_pfn = page_to_pfn(sg_page(sg)) >> 9;
+ }
+
+ status = hv_do_rep_hypercall(HV_EXT_CALL_MEMORY_HEAT_HINT, nents, 0,
+ hint, NULL);
+ local_irq_restore(flags);
+ status &= HV_HYPERCALL_RESULT_MASK;
+ if (status != HV_STATUS_SUCCESS) {
+ pr_err("Cold memory discard hypercall failed with status %llx\n",
+ status);
+ return -1;
+ }
+
+ return 0;
+}
+
+static int enable_page_reporting(void)
+{
+ int ret;
+
+ if (!(hv_query_ext_cap() &
+ HV_EXT_CAPABILITY_MEMORY_COLD_DISCARD_HINT)) {
+ pr_info("Cold memory discard hint not supported by Hyper-V\n");
+ return 0;
+ }
+
+ BUILD_BUG_ON(PAGE_REPORTING_CAPACITY > HV_MAX_GPA_PAGE_RANGES);
+ dm_device.pr_dev_info.report = hv_free_page_report;
+ ret = page_reporting_register(&dm_device.pr_dev_info);
+ if (ret < 0) {
+ dm_device.pr_dev_info.report = NULL;
+ pr_err("Failed to enable cold memory discard: %d\n", ret);
+ } else {
+ pr_info("Cold memory discard hint enabled\n");
+ }
+
+ return ret;
+}
+
+static void disable_page_reporting(void)
+{
+ if (dm_device.pr_dev_info.report) {
+ page_reporting_unregister(&dm_device.pr_dev_info);
+ dm_device.pr_dev_info.report = NULL;
+ }
+}
+#endif //CONFIG_PAGE_REPORTING
+
static int balloon_connect_vsp(struct hv_device *dev)
{
struct dm_version_request version_req;
@@ -1710,6 +1792,11 @@ static int balloon_probe(struct hv_device *dev,
if (ret != 0)
return ret;

+#ifdef CONFIG_PAGE_REPORTING
+ if (enable_page_reporting() < 0)
+ goto probe_error;
+#endif
+
dm_device.state = DM_INITIALIZED;

dm_device.thread =
@@ -1728,6 +1815,9 @@ static int balloon_probe(struct hv_device *dev,
#ifdef CONFIG_MEMORY_HOTPLUG
unregister_memory_notifier(&hv_memory_nb);
restore_online_page_callback(&hv_online_page);
+#endif
+#ifdef CONFIG_PAGE_REPORTING
+ disable_page_reporting();
#endif
return ret;
}
@@ -1750,6 +1840,9 @@ static int balloon_remove(struct hv_device *dev)
#ifdef CONFIG_MEMORY_HOTPLUG
unregister_memory_notifier(&hv_memory_nb);
restore_online_page_callback(&hv_online_page);
+#endif
+#ifdef CONFIG_PAGE_REPORTING
+ disable_page_reporting();
#endif
spin_lock_irqsave(&dm_device.ha_lock, flags);
list_for_each_entry_safe(has, tmp, &dm->ha_region_list, list) {
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index 262fae9526b1..75aeea0e7f9b 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -89,6 +89,7 @@
#define HV_ACCESS_STATS BIT(8)
#define HV_DEBUGGING BIT(11)
#define HV_CPU_POWER_MANAGEMENT BIT(12)
+#define HV_ENABLE_EXTENDED_HYPERCALLS BIT(20)


/*
@@ -149,11 +150,18 @@ struct ms_hyperv_tsc_page {
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0

+/* Extended hypercalls */
+#define HV_EXT_CALL_QUERY_CAPABILITIES 0x8001
+#define HV_EXT_CALL_MEMORY_HEAT_HINT 0x8003
+
#define HV_FLUSH_ALL_PROCESSORS BIT(0)
#define HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES BIT(1)
#define HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY BIT(2)
#define HV_FLUSH_USE_EXTENDED_RANGE_FORMAT BIT(3)

+/* Extended capability bits */
+#define HV_EXT_CAPABILITY_MEMORY_COLD_DISCARD_HINT BIT(8)
+
enum HV_GENERIC_SET_FORMAT {
HV_GENERIC_SET_SPARSE_4K,
HV_GENERIC_SET_ALL,
@@ -371,6 +379,12 @@ union hv_gpa_page_range {
u64 largepage:1;
u64 basepfn:52;
} page;
+ struct {
+ u64:12;
+ u64 page_size:1;
+ u64 reserved:8;
+ u64 base_large_pfn:43;
+ };
};

/*
@@ -490,4 +504,19 @@ struct hv_set_vp_registers_input {
} element[];
} __packed;

+/*
+ * The whole argument should fit in a page to be able to pass to the hypervisor
+ * in one hypercall.
+ */
+#define HV_MAX_GPA_PAGE_RANGES ((PAGE_SIZE - sizeof(u64)) / \
+ sizeof(union hv_gpa_page_range))
+
+/* HvExtCallMemoryHeatHint hypercall */
+#define HV_EXT_MEMORY_HEAT_HINT_TYPE_COLD_DISCARD 2
+struct hv_memory_hint {
+ u64 type:2;
+ u64 reserved:62;
+ union hv_gpa_page_range ranges[1];
+};
+
#endif
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 1c4fd950f091..c664af4a7503 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -27,6 +27,7 @@

struct ms_hyperv_info {
u32 features;
+ u32 b_features;
u32 misc_features;
u32 hints;
u32 nested_features;
@@ -169,6 +170,7 @@ bool hv_is_hyperv_initialized(void);
bool hv_is_hibernation_supported(void);
void hyperv_cleanup(void);
void hv_setup_sched_clock(void *sched_clock);
+u64 hv_query_ext_cap(void);
#else /* CONFIG_HYPERV */
static inline bool hv_is_hyperv_initialized(void) { return false; }
static inline bool hv_is_hibernation_supported(void) { return false; }
--
2.17.1
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