From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8700028B415; Fri, 17 Oct 2025 23:55:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760745329; cv=none; b=HyoS6fz8+0RqWRuoeVvslU8RCVbO+gkyN1FfL2UpF18Dgc9KOkiRxkrGGUMTxQ3PbwUO/gUP5JAe9bbv0QGdQjyX7RBB3i+jFJyA3jrplFhBpMt6AlPxm4QN82gjzfTkCIMsCbsnIspkYZsCtGrGu+pfGIKGudAvVw2ibTwAYLA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760745329; c=relaxed/simple; bh=bMisvaFs5OLSC2A5w/a4TrWMIMnGhK5d5PiEglWtrZk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UVSVGFqWzhvv3ozltXzkxI4WQit+HT4CD1aeWWy+8NXEJYXwC+RZZi1XTgAhSe0BsCE+jBVQ6EFeZbBLO6UgsRxZZ6yObLeHN+kEmfVtvyf1+tbvbl+u98oaE8OVyL+Wx4/GpJN5NJj0scWsPJ4+UtB/gKMXCZ29/D4EMPUmclY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=DHFSawNl; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="DHFSawNl" Received: from [100.75.0.68] (unknown [40.78.13.173]) by linux.microsoft.com (Postfix) with ESMTPSA id 6B6692017270; Fri, 17 Oct 2025 16:55:25 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 6B6692017270 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1760745325; bh=69XA6NT+DA3RKBhDsoEM5uBbcrPC+Jzo2Stuv7qKURI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=DHFSawNl8cTt+UXXlvx/Ddfjg19Ti6VjfonrIz9a2s1iCDklI9JgYDpSp+fNdUZuI V0ZwnuMRasy0CCdH+CYZL6UznhKG1ODVun3HEAcWGvU5M/2UCJzp0TX93Jkubk5G95 qC0gMBPUF8cvsaaC9R4qeCk+s+jJz8ehcr1yaoxw= Message-ID: <2d5d540c-6ed5-455f-a895-9a3dd12bae2c@linux.microsoft.com> Date: Fri, 17 Oct 2025 16:55:24 -0700 Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.13.1 Subject: Re: [PATCH v5 5/5] Drivers: hv: Add support for movable memory regions Content-Language: en-US To: Stanislav Kinsburskii , kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org References: <176057396465.74314.10055784909009416453.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net> <176057443695.74314.10584965103467299030.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net> From: Mukesh R In-Reply-To: <176057443695.74314.10584965103467299030.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/15/25 17:27, Stanislav Kinsburskii wrote: > Introduce support for movable memory regions in the Hyper-V root partition > driver, thus improving memory management flexibility and preparing the > driver for advanced use cases such as dynamic memory remapping. > > Integrate mmu_interval_notifier for movable regions, implement functions to > handle HMM faults and memory invalidation, and update memory region mapping > logic to support movable regions. > > While MMU notifiers are commonly used in virtualization drivers, this > implementation leverages HMM (Heterogeneous Memory Management) for its > tailored functionality. HMM provides a ready-made framework for mirroring, > invalidation, and fault handling, avoiding the need to reimplement these > mechanisms for a single callback. Although MMU notifiers are more generic, > using HMM reduces boilerplate and ensures maintainability by utilizing a > mechanism specifically designed for such use cases. > > Signed-off-by: Anirudh Rayabharam > Signed-off-by: Stanislav Kinsburskii > --- > drivers/hv/Kconfig | 1 > drivers/hv/mshv_root.h | 8 + > drivers/hv/mshv_root_main.c | 328 ++++++++++++++++++++++++++++++++++++++++++- > 3 files changed, 327 insertions(+), 10 deletions(-) > > diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig > index 0b8c391a0342..5f1637cbb6e3 100644 > --- a/drivers/hv/Kconfig > +++ b/drivers/hv/Kconfig > @@ -75,6 +75,7 @@ config MSHV_ROOT > depends on PAGE_SIZE_4KB > select EVENTFD > select VIRT_XFER_TO_GUEST_WORK > + select HMM_MIRROR > default n > help > Select this option to enable support for booting and running as root > diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h > index 97e64d5341b6..13367c84497c 100644 > --- a/drivers/hv/mshv_root.h > +++ b/drivers/hv/mshv_root.h > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > #include > > /* > @@ -81,9 +82,14 @@ struct mshv_mem_region { > struct { > u64 large_pages: 1; /* 2MiB */ > u64 range_pinned: 1; > - u64 reserved: 62; > + u64 is_ram : 1; /* mem region can be ram or mmio */ In case this gets accepted/merged, this is named + u64 memreg_isram: 1; /* mem region can be ram or mmio */ Keeping the name same will avoid unnecessary diffs when we try to compare files to see what is missing internally or externally. Thanks, -Mukesh > } flags; > struct mshv_partition *partition; > +#if defined(CONFIG_MMU_NOTIFIER) > + struct mmu_interval_notifier mni; > + struct mutex mutex; /* protects region pages remapping */ > +#endif > struct page *pages[]; > }; > > diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c > index c4f114376435..b2738443ac5d 100644 > --- a/drivers/hv/mshv_root_main.c > +++ b/drivers/hv/mshv_root_main.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > > #include "mshv_eventfd.h" > #include "mshv.h" > @@ -36,6 +37,8 @@ > > #define VALUE_PMD_ALIGNED(c) (!((c) & (PTRS_PER_PMD - 1))) > > +#define MSHV_MAP_FAULT_IN_PAGES HPAGE_PMD_NR > + > MODULE_AUTHOR("Microsoft"); > MODULE_LICENSE("GPL"); > MODULE_DESCRIPTION("Microsoft Hyper-V root partition VMM interface /dev/mshv"); > @@ -76,6 +79,11 @@ static int mshv_vp_mmap(struct file *file, struct vm_area_struct *vma); > static vm_fault_t mshv_vp_fault(struct vm_fault *vmf); > static int mshv_init_async_handler(struct mshv_partition *partition); > static void mshv_async_hvcall_handler(void *data, u64 *status); > +static struct mshv_mem_region > + *mshv_partition_region_by_gfn(struct mshv_partition *pt, u64 gfn); > +static int mshv_region_remap_pages(struct mshv_mem_region *region, > + u32 map_flags, u64 page_offset, > + u64 page_count); > > static const union hv_input_vtl input_vtl_zero; > static const union hv_input_vtl input_vtl_normal = { > @@ -602,14 +610,197 @@ static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp) > static_assert(sizeof(struct hv_message) <= MSHV_RUN_VP_BUF_SZ, > "sizeof(struct hv_message) must not exceed MSHV_RUN_VP_BUF_SZ"); > > +#ifdef CONFIG_X86_64 > + > +#if defined(CONFIG_MMU_NOTIFIER) > +/** > + * mshv_region_hmm_fault_and_lock - Handle HMM faults and lock the memory region > + * @region: Pointer to the memory region structure > + * @range: Pointer to the HMM range structure > + * > + * This function performs the following steps: > + * 1. Reads the notifier sequence for the HMM range. > + * 2. Acquires a read lock on the memory map. > + * 3. Handles HMM faults for the specified range. > + * 4. Releases the read lock on the memory map. > + * 5. If successful, locks the memory region mutex. > + * 6. Verifies if the notifier sequence has changed during the operation. > + * If it has, releases the mutex and returns -EBUSY to match with > + * hmm_range_fault() return code for repeating. > + * > + * Return: 0 on success, a negative error code otherwise. > + */ > +static int mshv_region_hmm_fault_and_lock(struct mshv_mem_region *region, > + struct hmm_range *range) > +{ > + int ret; > + > + range->notifier_seq = mmu_interval_read_begin(range->notifier); > + mmap_read_lock(region->mni.mm); > + ret = hmm_range_fault(range); > + mmap_read_unlock(region->mni.mm); > + if (ret) > + return ret; > + > + mutex_lock(®ion->mutex); > + > + if (mmu_interval_read_retry(range->notifier, range->notifier_seq)) { > + mutex_unlock(®ion->mutex); > + cond_resched(); > + return -EBUSY; > + } > + > + return 0; > +} > + > +/** > + * mshv_region_range_fault - Handle memory range faults for a given region. > + * @region: Pointer to the memory region structure. > + * @page_offset: Offset of the page within the region. > + * @page_count: Number of pages to handle. > + * > + * This function resolves memory faults for a specified range of pages > + * within a memory region. It uses HMM (Heterogeneous Memory Management) > + * to fault in the required pages and updates the region's page array. > + * > + * Return: 0 on success, negative error code on failure. > + */ > +static int mshv_region_range_fault(struct mshv_mem_region *region, > + u64 page_offset, u64 page_count) > +{ > + struct hmm_range range = { > + .notifier = ®ion->mni, > + .default_flags = HMM_PFN_REQ_FAULT | HMM_PFN_REQ_WRITE, > + }; > + unsigned long *pfns; > + int ret; > + u64 i; > + > + pfns = kmalloc_array(page_count, sizeof(unsigned long), GFP_KERNEL); > + if (!pfns) > + return -ENOMEM; > + > + range.hmm_pfns = pfns; > + range.start = region->start_uaddr + page_offset * HV_HYP_PAGE_SIZE; > + range.end = range.start + page_count * HV_HYP_PAGE_SIZE; > + > + do { > + ret = mshv_region_hmm_fault_and_lock(region, &range); > + } while (ret == -EBUSY); > + > + if (ret) > + goto out; > + > + for (i = 0; i < page_count; i++) > + region->pages[page_offset + i] = hmm_pfn_to_page(pfns[i]); > + > + if (PageHuge(region->pages[page_offset])) > + region->flags.large_pages = true; > + > + ret = mshv_region_remap_pages(region, region->hv_map_flags, > + page_offset, page_count); > + > + mutex_unlock(®ion->mutex); > +out: > + kfree(pfns); > + return ret; > +} > +#else /* CONFIG_MMU_NOTIFIER */ > +static int mshv_region_range_fault(struct mshv_mem_region *region, > + u64 page_offset, u64 page_count) > +{ > + return -ENODEV; > +} > +#endif /* CONFIG_MMU_NOTIFIER */ > + > +static bool mshv_region_handle_gfn_fault(struct mshv_mem_region *region, u64 gfn) > +{ > + u64 page_offset, page_count; > + int ret; > + > + if (WARN_ON_ONCE(region->flags.range_pinned)) > + return false; > + > + /* Align the page offset to the nearest MSHV_MAP_FAULT_IN_PAGES. */ > + page_offset = ALIGN_DOWN(gfn - region->start_gfn, > + MSHV_MAP_FAULT_IN_PAGES); > + > + /* Map more pages than requested to reduce the number of faults. */ > + page_count = min(region->nr_pages - page_offset, > + MSHV_MAP_FAULT_IN_PAGES); > + > + ret = mshv_region_range_fault(region, page_offset, page_count); > + > + WARN_ONCE(ret, > + "p%llu: GPA intercept failed: region %#llx-%#llx, gfn %#llx, page_offset %llu, page_count %llu\n", > + region->partition->pt_id, region->start_uaddr, > + region->start_uaddr + (region->nr_pages << HV_HYP_PAGE_SHIFT), > + gfn, page_offset, page_count); > + > + return !ret; > +} > + > +/** > + * mshv_handle_gpa_intercept - Handle GPA (Guest Physical Address) intercepts. > + * @vp: Pointer to the virtual processor structure. > + * > + * This function processes GPA intercepts by identifying the memory region > + * corresponding to the intercepted GPA, aligning the page offset, and > + * mapping the required pages. It ensures that the region is valid and > + * handles faults efficiently by mapping multiple pages at once. > + * > + * Return: true if the intercept was handled successfully, false otherwise. > + */ > +static bool mshv_handle_gpa_intercept(struct mshv_vp *vp) > +{ > + struct mshv_partition *p = vp->vp_partition; > + struct mshv_mem_region *region; > + struct hv_x64_memory_intercept_message *msg; > + u64 gfn; > + > + msg = (struct hv_x64_memory_intercept_message *) > + vp->vp_intercept_msg_page->u.payload; > + > + gfn = HVPFN_DOWN(msg->guest_physical_address); > + > + region = mshv_partition_region_by_gfn(p, gfn); > + if (!region) > + return false; > + > + if (WARN_ON_ONCE(!region->flags.is_ram)) > + return false; > + > + if (WARN_ON_ONCE(region->flags.range_pinned)) > + return false; > + > + return mshv_region_handle_gfn_fault(region, gfn); > +} > + > +#else /* CONFIG_X86_64 */ > + > +static bool mshv_handle_gpa_intercept(struct mshv_vp *vp) { return false; } > + > +#endif /* CONFIG_X86_64 */ > + > +static bool mshv_vp_handle_intercept(struct mshv_vp *vp) > +{ > + switch (vp->vp_intercept_msg_page->header.message_type) { > + case HVMSG_GPA_INTERCEPT: > + return mshv_handle_gpa_intercept(vp); > + } > + return false; > +} > + > static long mshv_vp_ioctl_run_vp(struct mshv_vp *vp, void __user *ret_msg) > { > long rc; > > - if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT) > - rc = mshv_run_vp_with_root_scheduler(vp); > - else > - rc = mshv_run_vp_with_hyp_scheduler(vp); > + do { > + if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT) > + rc = mshv_run_vp_with_root_scheduler(vp); > + else > + rc = mshv_run_vp_with_hyp_scheduler(vp); > + } while (rc == 0 && mshv_vp_handle_intercept(vp)); > > if (rc) > return rc; > @@ -1209,6 +1400,110 @@ mshv_partition_region_by_uaddr(struct mshv_partition *partition, u64 uaddr) > return NULL; > } > > +#if defined(CONFIG_MMU_NOTIFIER) > +static void mshv_region_movable_fini(struct mshv_mem_region *region) > +{ > + if (region->flags.range_pinned) > + return; > + > + mmu_interval_notifier_remove(®ion->mni); > +} > + > +/** > + * mshv_region_interval_invalidate - Invalidate a range of memory region > + * @mni: Pointer to the mmu_interval_notifier structure > + * @range: Pointer to the mmu_notifier_range structure > + * @cur_seq: Current sequence number for the interval notifier > + * > + * This function invalidates a memory region by remapping its pages with > + * no access permissions. It locks the region's mutex to ensure thread safety > + * and updates the sequence number for the interval notifier. If the range > + * is blockable, it uses a blocking lock; otherwise, it attempts a non-blocking > + * lock and returns false if unsuccessful. > + * > + * NOTE: Failure to invalidate a region is a serious error, as the pages will > + * be considered freed while they are still mapped by the hypervisor. > + * Any attempt to access such pages will likely crash the system. > + * > + * Return: true if the region was successfully invalidated, false otherwise. > + */ > +static bool > +mshv_region_interval_invalidate(struct mmu_interval_notifier *mni, > + const struct mmu_notifier_range *range, > + unsigned long cur_seq) > +{ > + struct mshv_mem_region *region = container_of(mni, > + struct mshv_mem_region, > + mni); > + u64 page_offset, page_count; > + unsigned long mstart, mend; > + int ret = -EPERM; > + > + if (mmu_notifier_range_blockable(range)) > + mutex_lock(®ion->mutex); > + else if (!mutex_trylock(®ion->mutex)) > + goto out_fail; > + > + mmu_interval_set_seq(mni, cur_seq); > + > + mstart = max(range->start, region->start_uaddr); > + mend = min(range->end, region->start_uaddr + > + (region->nr_pages << HV_HYP_PAGE_SHIFT)); > + > + page_offset = HVPFN_DOWN(mstart - region->start_uaddr); > + page_count = HVPFN_DOWN(mend - mstart); > + > + ret = mshv_region_remap_pages(region, HV_MAP_GPA_NO_ACCESS, > + page_offset, page_count); > + if (ret) > + goto out_fail; > + > + mshv_region_invalidate_pages(region, page_offset, page_count); > + > + mutex_unlock(®ion->mutex); > + > + return true; > + > +out_fail: > + WARN_ONCE(ret, > + "Failed to invalidate region %#llx-%#llx (range %#lx-%#lx, event: %u, pages %#llx-%#llx, mm: %#llx): %d\n", > + region->start_uaddr, > + region->start_uaddr + (region->nr_pages << HV_HYP_PAGE_SHIFT), > + range->start, range->end, range->event, > + page_offset, page_offset + page_count - 1, (u64)range->mm, ret); > + return false; > +} > + > +static const struct mmu_interval_notifier_ops mshv_region_mni_ops = { > + .invalidate = mshv_region_interval_invalidate, > +}; > + > +static bool mshv_region_movable_init(struct mshv_mem_region *region) > +{ > + int ret; > + > + ret = mmu_interval_notifier_insert(®ion->mni, current->mm, > + region->start_uaddr, > + region->nr_pages << HV_HYP_PAGE_SHIFT, > + &mshv_region_mni_ops); > + if (ret) > + return false; > + > + mutex_init(®ion->mutex); > + > + return true; > +} > +#else > +static inline void mshv_region_movable_fini(struct mshv_mem_region *region) > +{ > +} > + > +static inline bool mshv_region_movable_init(struct mshv_mem_region *region) > +{ > + return false; > +} > +#endif > + > /* > * NB: caller checks and makes sure mem->size is page aligned > * Returns: 0 with regionpp updated on success, or -errno > @@ -1241,9 +1536,14 @@ static int mshv_partition_create_region(struct mshv_partition *partition, > if (mem->flags & BIT(MSHV_SET_MEM_BIT_EXECUTABLE)) > region->hv_map_flags |= HV_MAP_GPA_EXECUTABLE; > > - /* Note: large_pages flag populated when we pin the pages */ > - if (!is_mmio) > - region->flags.range_pinned = true; > + /* Note: large_pages flag populated when pages are allocated. */ > + if (!is_mmio) { > + region->flags.is_ram = true; > + > + if (mshv_partition_encrypted(partition) || > + !mshv_region_movable_init(region)) > + region->flags.range_pinned = true; > + } > > region->partition = partition; > > @@ -1363,9 +1663,16 @@ mshv_map_user_memory(struct mshv_partition *partition, > if (is_mmio) > ret = hv_call_map_mmio_pages(partition->pt_id, mem.guest_pfn, > mmio_pfn, HVPFN_DOWN(mem.size)); > - else > + else if (region->flags.range_pinned) > ret = mshv_prepare_pinned_region(region); > - > + else > + /* > + * For non-pinned regions, remap with no access to let the > + * hypervisor track dirty pages, enabling pre-copy live > + * migration. > + */ > + ret = mshv_region_remap_pages(region, HV_MAP_GPA_NO_ACCESS, > + 0, region->nr_pages); > if (ret) > goto errout; > > @@ -1388,6 +1695,9 @@ static void mshv_partition_destroy_region(struct mshv_mem_region *region) > > hlist_del(®ion->hnode); > > + if (region->flags.is_ram) > + mshv_region_movable_fini(region); > + > if (mshv_partition_encrypted(partition)) { > ret = mshv_partition_region_share(region); > if (ret) { > >