On 2/8/2021 11:44 AM, Michael Kelley wrote: > From: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> Sent: Friday, November 20, 2020 4:30 PM >> >> Withdraw the memory from a finalized partition and free the pages. >> The partition is now cleaned up correctly when the fd is released. >> >> Co-developed-by: Lillian Grassin-Drake <ligrassi@xxxxxxxxxxxxx> >> Signed-off-by: Lillian Grassin-Drake <ligrassi@xxxxxxxxxxxxx> >> Signed-off-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> >> --- >> include/asm-generic/hyperv-tlfs.h | 10 ++++++ >> virt/mshv/mshv_main.c | 54 ++++++++++++++++++++++++++++++- >> 2 files changed, 63 insertions(+), 1 deletion(-) >> >> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h >> index ab6ae6c164f5..2a49503b7396 100644 >> --- a/include/asm-generic/hyperv-tlfs.h >> +++ b/include/asm-generic/hyperv-tlfs.h >> @@ -148,6 +148,7 @@ struct ms_hyperv_tsc_page { >> #define HVCALL_DELETE_PARTITION 0x0043 >> #define HVCALL_GET_PARTITION_ID 0x0046 >> #define HVCALL_DEPOSIT_MEMORY 0x0048 >> +#define HVCALL_WITHDRAW_MEMORY 0x0049 >> #define HVCALL_CREATE_VP 0x004e >> #define HVCALL_GET_VP_REGISTERS 0x0050 >> #define HVCALL_SET_VP_REGISTERS 0x0051 >> @@ -472,6 +473,15 @@ union hv_proximity_domain_info { >> u64 as_uint64; >> }; >> >> +struct hv_withdraw_memory_in { >> + u64 partition_id; >> + union hv_proximity_domain_info proximity_domain_info; >> +}; >> + >> +struct hv_withdraw_memory_out { >> + u64 gpa_page_list[0]; > > For a variable size array, the Linux kernel community has an effort > underway to replace occurrences of [0] and [1] with just []. I think > [] can be used here. > It seems the compiler doesn't like that, because there's no other members in the struct? ./include/asm-generic/hyperv-tlfs.h:452:6: error: flexible array member in a struct with no named members 452 | u64 gpa_page_list[]; I'll add a comment explaining that it's a hack to work around the compiler. >> +}; >> + > > Add __packed to the above two structs. > Will do. >> struct hv_lp_startup_status { >> u64 hv_status; >> u64 substatus1; >> diff --git a/virt/mshv/mshv_main.c b/virt/mshv/mshv_main.c >> index c4130a6508e5..162a1bb42a4a 100644 >> --- a/virt/mshv/mshv_main.c >> +++ b/virt/mshv/mshv_main.c >> @@ -14,6 +14,7 @@ >> #include <linux/slab.h> >> #include <linux/file.h> >> #include <linux/anon_inodes.h> >> +#include <linux/mm.h> >> #include <linux/mshv.h> >> #include <asm/mshyperv.h> >> >> @@ -57,8 +58,58 @@ static struct miscdevice mshv_dev = { >> .mode = 600, >> }; >> >> +#define HV_WITHDRAW_BATCH_SIZE (PAGE_SIZE / sizeof(u64)) > > Use HV_HYP_PAGE_SIZE so that we're explicit that the dependency > is on the page size used by Hyper-V, which might be different from the > guest page size (at least on architectures like ARM64). > Yes, will do. >> #define HV_INIT_PARTITION_DEPOSIT_PAGES 208 >> >> +static int >> +hv_call_withdraw_memory(u64 count, int node, u64 partition_id) >> +{ >> + struct hv_withdraw_memory_in *input_page; >> + struct hv_withdraw_memory_out *output_page; >> + u16 completed; >> + u64 hypercall_status; >> + unsigned long remaining = count; >> + int status; >> + int i; >> + unsigned long flags; >> + >> + while (remaining) { >> + local_irq_save(flags); >> + >> + input_page = (struct hv_withdraw_memory_in *)(*this_cpu_ptr( >> + hyperv_pcpu_input_arg)); >> + output_page = (struct hv_withdraw_memory_out *)(*this_cpu_ptr( >> + hyperv_pcpu_output_arg)); >> + >> + input_page->partition_id = partition_id; >> + input_page->proximity_domain_info.as_uint64 = 0; >> + hypercall_status = hv_do_rep_hypercall( >> + HVCALL_WITHDRAW_MEMORY, >> + min(remaining, HV_WITHDRAW_BATCH_SIZE), 0, input_page, >> + output_page); >> + >> + completed = (hypercall_status & HV_HYPERCALL_REP_COMP_MASK) >> >> + HV_HYPERCALL_REP_COMP_OFFSET; >> + >> + for (i = 0; i < completed; i++) >> + __free_page(pfn_to_page(output_page->gpa_page_list[i])); >> + >> + local_irq_restore(flags); > > Seems like there's some risk that we have interrupts disabled for too long. > We could be calling __free_page() up to 512 times. It might be better for this > function to allocate its own page to be used as the output page, so that interrupts > can be enabled immediately after the hypercall completes. Then the __free_page() > loop can execute with interrupts enabled. We have the per-cpu input and output > pages to avoid the overhead of allocating/freeing pages for each hypercall, but in this > case a private output page might be warranted. > Good idea, I'll do that. >> + >> + status = hypercall_status & HV_HYPERCALL_RESULT_MASK; >> + if (status != HV_STATUS_SUCCESS) { >> + if (status != HV_STATUS_NO_RESOURCES) >> + pr_err("%s: %s\n", __func__, >> + hv_status_to_string(status)); >> + break; >> + } >> + >> + remaining -= completed; >> + } >> + >> + return -hv_status_to_errno(status); >> +} >> + >> static int >> hv_call_create_partition( >> u64 flags, >> @@ -230,7 +281,8 @@ destroy_partition(struct mshv_partition *partition) >> >> /* Deallocates and unmaps everything including vcpus, GPA mappings etc */ >> hv_call_finalize_partition(partition->id); >> - /* TODO: Withdraw and free all pages we deposited */ >> + /* Withdraw and free all pages we deposited */ >> + hv_call_withdraw_memory(U64_MAX, NUMA_NO_NODE, partition->id); >> >> hv_call_delete_partition(partition->id); >> >> -- >> 2.25.1