On Tue, Mar 23, 2021 at 06:47:16PM +0000, Sunil Muthuswamy wrote:
> 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@xxxxxxxxxxxxx>
> Tested-by: Matheus Castello <matheus@xxxxxxxxxxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> ---
> In V2:
> - Addressed feedback comments
> - Added page reporting config option tied to hyper-v balloon config
>
> In V3:
> - Addressed feedback from Vitaly
>
> In V4:
> - Queried and cached the Hyper-V extended capability for the lifetime
> of the VM
> - Addressed feedback from Michael Kelley.
>
> In v5:
> - Added a comment clarifying handling of failed query extended
> capability hypercall to address Michael's feedback.
> ---
> arch/x86/hyperv/hv_init.c | 51 +++++++++++++++++-
> arch/x86/kernel/cpu/mshyperv.c | 9 ++--
> drivers/hv/Kconfig | 1 +
> drivers/hv/hv_balloon.c | 89 +++++++++++++++++++++++++++++++
> include/asm-generic/hyperv-tlfs.h | 35 +++++++++++-
> include/asm-generic/mshyperv.h | 3 +-
> 6 files changed, 180 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 9d100257b3af..7c9da3f65afa 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -498,6 +498,8 @@ void __init hyperv_init(void)
> x86_init.irqs.create_pci_msi_domain = hv_create_pci_msi_domain;
> #endif
>
> + /* Query the VMs extended capability once, so that it can be cached. */
> + hv_query_ext_cap(0);
> return;
>
> remove_cpuhp_state:
> @@ -601,7 +603,7 @@ EXPORT_SYMBOL_GPL(hv_is_hibernation_supported);
>
> enum hv_isolation_type hv_get_isolation_type(void)
> {
> - if (!(ms_hyperv.features_b & HV_ISOLATION))
> + if (!(ms_hyperv.priv_high & HV_ISOLATION))
> return HV_ISOLATION_TYPE_NONE;
> return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
> }
> @@ -612,3 +614,50 @@ bool hv_is_isolation_supported(void)
> return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
> }
> EXPORT_SYMBOL_GPL(hv_is_isolation_supported);
> +
> +/* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
> +bool hv_query_ext_cap(u64 cap_query)
> +{
> + /*
> + * The address of the 'hv_extended_cap' variable will be used as an
> + * output parameter to the hypercall below and so it should be
> + * compatible with 'virt_to_phys'. Which means, it's address should be
> + * directly mapped. Use 'static' to keep it compatible; stack variables
> + * can be virtually mapped, making them imcompatible with
> + * 'virt_to_phys'.
> + * Hypercall input/output addresses should also be 8-byte aligned.
> + */
> + static u64 hv_extended_cap __aligned(8);
> + static bool hv_extended_cap_queried;
> + u64 status;
> +
> + /*
> + * Querying extended capabilities is an extended hypercall. Check if the
> + * partition supports extended hypercall, first.
> + */
> + if (!(ms_hyperv.priv_high & HV_ENABLE_EXTENDED_HYPERCALLS))
> + return false;
> +
> + /* Extended capabilities do not change at runtime. */
> + if (hv_extended_cap_queried)
> + return hv_extended_cap & cap_query;
> +
> + status = hv_do_hypercall(HV_EXT_CALL_QUERY_CAPABILITIES, NULL,
> + &hv_extended_cap);
> +
> + /*
> + * The query extended capabilities hypercall should not fail under
> + * any normal circumstances. Avoid repeatedly making the hypercall, on
> + * error.
> + */
> + hv_extended_cap_queried = true;
> + status &= HV_HYPERCALL_RESULT_MASK;
> + if (status != HV_STATUS_SUCCESS) {
> + pr_err("Hyper-V: Extended query capabilities hypercall failed 0x%llx\n",
> + status);
> + return false;
> + }
> +
> + return hv_extended_cap & cap_query;
> +}
> +EXPORT_SYMBOL_GPL(hv_query_ext_cap);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index cebed535ec56..3546d3e21787 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -265,12 +265,13 @@ static void __init ms_hyperv_init_platform(void)
> * Extract the features and hints
> */
> ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
> - ms_hyperv.features_b = cpuid_ebx(HYPERV_CPUID_FEATURES);
> + ms_hyperv.priv_high = 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: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
> + ms_hyperv.features, ms_hyperv.priv_high, 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);
> @@ -316,7 +317,7 @@ static void __init ms_hyperv_init_platform(void)
> x86_platform.calibrate_cpu = hv_get_tsc_khz;
> }
>
> - if (ms_hyperv.features_b & HV_ISOLATION) {
> + if (ms_hyperv.priv_high & HV_ISOLATION) {
> ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
> ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
>
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 79e5356a737a..66c794d92391 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -23,6 +23,7 @@ config HYPERV_UTILS
> config HYPERV_BALLOON
> tristate "Microsoft Hyper-V Balloon driver"
> depends on HYPERV
> + select PAGE_REPORTING
> help
> Select this option to enable Hyper-V Balloon driver.
>
> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> index 2f776d78e3c1..58af84e30144 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 +564,8 @@ struct hv_dynmem_device {
> * The negotiated version agreed by host.
> */
> __u32 version;
> +
> + struct page_reporting_dev_info pr_dev_info;
> };
>
> static struct hv_dynmem_device dm_device;
> @@ -1568,6 +1571,89 @@ static void balloon_onchannelcallback(void *context)
>
> }
>
> +/* Hyper-V only supports reporting 2MB pages or higher */
> +#define HV_MIN_PAGE_REPORTING_ORDER 9
> +#define HV_MIN_PAGE_REPORTING_LEN (HV_HYP_PAGE_SIZE << HV_MIN_PAGE_REPORTING_ORDER)
> +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_ONCE(nents > HV_MEMORY_HINT_MAX_GPA_PAGE_RANGES);
> + WARN_ON_ONCE(sgl->length < HV_MIN_PAGE_REPORTING_LEN);
> + 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_each_sg(sgl, sg, nents, i) {
> + union hv_gpa_page_range *range;
> +
> + range = &hint->ranges[i];
> + range->address_space = 0;
> + /* page reporting only reports 2MB pages or higher */
> + range->page.largepage = 1;
> + range->page.additional_pages =
> + (sg->length / HV_MIN_PAGE_REPORTING_LEN) - 1;
> + range->page_size = HV_GPA_PAGE_RANGE_PAGE_SIZE_2MB;
> + range->base_large_pfn =
> + page_to_hvpfn(sg_page(sg)) >> HV_MIN_PAGE_REPORTING_ORDER;
> + }
> +
> + status = hv_do_rep_hypercall(HV_EXT_CALL_MEMORY_HEAT_HINT, nents, 0,
> + hint, NULL);
> + local_irq_restore(flags);
> + if ((status & HV_HYPERCALL_RESULT_MASK) != HV_STATUS_SUCCESS) {
> + pr_err("Cold memory discard hypercall failed with status %llx\n",
> + status);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static void enable_page_reporting(void)
> +{
> + int ret;
> +
> + /* Essentially, validating 'PAGE_REPORTING_MIN_ORDER' is big enough. */
> + if (pageblock_order < HV_MIN_PAGE_REPORTING_ORDER) {
> + pr_debug("Cold memory discard is only supported on 2MB pages and above\n");
> + return;
> + }
> +
> + if (!hv_query_ext_cap(HV_EXT_CAPABILITY_MEMORY_COLD_DISCARD_HINT)) {
> + pr_debug("Cold memory discard hint not supported by Hyper-V\n");
> + return;
> + }
> +
> + BUILD_BUG_ON(PAGE_REPORTING_CAPACITY > HV_MEMORY_HINT_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");
> + }
> +}
> +
> +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;
> + }
> +}
> +
> static int balloon_connect_vsp(struct hv_device *dev)
> {
> struct dm_version_request version_req;
> @@ -1713,6 +1799,7 @@ static int balloon_probe(struct hv_device *dev,
> if (ret != 0)
> return ret;
>
> + enable_page_reporting();
> dm_device.state = DM_INITIALIZED;
>
> dm_device.thread =
> @@ -1727,6 +1814,7 @@ static int balloon_probe(struct hv_device *dev,
> probe_error:
> dm_device.state = DM_INIT_ERROR;
> dm_device.thread = NULL;
> + disable_page_reporting();
> vmbus_close(dev->channel);
> #ifdef CONFIG_MEMORY_HOTPLUG
> unregister_memory_notifier(&hv_memory_nb);
> @@ -1749,6 +1837,7 @@ static int balloon_remove(struct hv_device *dev)
> cancel_work_sync(&dm->ha_wrk.wrk);
>
> kthread_stop(dm->thread);
> + disable_page_reporting();
> vmbus_close(dev->channel);
> #ifdef CONFIG_MEMORY_HOTPLUG
> unregister_memory_notifier(&hv_memory_nb);
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
> index 9cf10837d005..515c3fb06ab3 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -89,9 +89,9 @@
> #define HV_ACCESS_STATS BIT(8)
> #define HV_DEBUGGING BIT(11)
> #define HV_CPU_MANAGEMENT BIT(12)
> +#define HV_ENABLE_EXTENDED_HYPERCALLS BIT(20)
> #define HV_ISOLATION BIT(22)
>
> -
> /*
> * TSC page layout.
> */
> @@ -159,11 +159,18 @@ 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,
> @@ -408,8 +415,10 @@ struct hv_guest_mapping_flush {
> * by the bitwidth of "additional_pages" in union hv_gpa_page_range.
> */
> #define HV_MAX_FLUSH_PAGES (2048)
> +#define HV_GPA_PAGE_RANGE_PAGE_SIZE_2MB 0
> +#define HV_GPA_PAGE_RANGE_PAGE_SIZE_1GB 1
>
> -/* HvFlushGuestPhysicalAddressList hypercall */
> +/* HvFlushGuestPhysicalAddressList, HvExtCallMemoryHeatHint hypercall */
> union hv_gpa_page_range {
> u64 address_space;
> struct {
> @@ -417,6 +426,12 @@ union hv_gpa_page_range {
> u64 largepage:1;
> u64 basepfn:52;
> } page;
> + struct {
> + u64 reserved:12;
> + u64 page_size:1;
> + u64 reserved1:8;
> + u64 base_large_pfn:43;
> + };
> };
>
> /*
> @@ -774,4 +789,20 @@ struct hv_input_unmap_device_interrupt {
> #define HV_SOURCE_SHADOW_NONE 0x0
> #define HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE 0x1
>
> +/*
> + * The whole argument should fit in a page to be able to pass to the hypervisor
> + * in one hypercall.
> + */
> +#define HV_MEMORY_HINT_MAX_GPA_PAGE_RANGES \
> + ((HV_HYP_PAGE_SIZE - sizeof(struct hv_memory_hint)) / \
> + 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[];
> +} __packed;
> +
> #endif
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 2d1b6cd9f000..63c0e579bf6d 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -27,7 +27,7 @@
>
> struct ms_hyperv_info {
> u32 features;
> - u32 features_b;
> + u32 priv_high;
> u32 misc_features;
> u32 hints;
> u32 nested_features;
> @@ -179,6 +179,7 @@ bool hv_is_hibernation_supported(void);
> enum hv_isolation_type hv_get_isolation_type(void);
> bool hv_is_isolation_supported(void);
> void hyperv_cleanup(void);
> +bool hv_query_ext_cap(u64 cap_query);
> #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
