From: Stanislav Kinsburskii <[email protected]> Sent: Tuesday, March 3, 2026 4:24 PM > > Deposit enough pages up front to avoid virtual processor creation failures > due to low memory. This also speeds up guest creation. A VP uses 25% more > pages in a partition with nested virtualization enabled, but the exact > number doesn't vary much, so deposit a fixed number of pages per VP that > works for nested virtualization. > > Move page depositing from the hypercall wrapper to the virtual processor > creation code. The required number of pages is based on empirical data. > This logic fits better in the virtual processor creation code than in the > hypercall wrapper. > > Also withdraw the deposited memory if virtual processor creation fails. > > Signed-off-by: Stanislav Kinsburskii <[email protected]> > --- > drivers/hv/hv_proc.c | 8 -------- > drivers/hv/mshv_root_main.c | 11 ++++++++++- > 2 files changed, 10 insertions(+), 9 deletions(-) > > diff --git a/drivers/hv/hv_proc.c b/drivers/hv/hv_proc.c > index 0f84a70def30..3d41f52efd9a 100644 > --- a/drivers/hv/hv_proc.c > +++ b/drivers/hv/hv_proc.c > @@ -251,14 +251,6 @@ int hv_call_create_vp(int node, u64 partition_id, u32 > vp_index, u32 flags) > unsigned long irq_flags; > int ret = 0; > > - /* Root VPs don't seem to need pages deposited */ > - if (partition_id != hv_current_partition_id) { > - /* The value 90 is empirically determined. It may change. */ > - ret = hv_call_deposit_pages(node, partition_id, 90); > - if (ret) > - return ret; > - } > - > do { > local_irq_save(irq_flags); > > diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c > index fbfc50de332c..48c842b6938d 100644 > --- a/drivers/hv/mshv_root_main.c > +++ b/drivers/hv/mshv_root_main.c > @@ -38,6 +38,7 @@ > /* The deposit values below are empirical and may need to be adjusted. */ > #define MSHV_PARTITION_DEPOSIT_PAGES (SZ_512K >> PAGE_SHIFT) > #define MSHV_PARTITION_DEPOSIT_PAGES_NESTED (20 * SZ_1M >> PAGE_SHIFT) > +#define MSHV_VP_DEPOSIT_PAGES (1 * SZ_1M >> > PAGE_SHIFT) > > MODULE_AUTHOR("Microsoft"); > MODULE_LICENSE("GPL"); > @@ -1077,10 +1078,15 @@ mshv_partition_ioctl_create_vp(struct mshv_partition > *partition, > if (partition->pt_vp_array[args.vp_index]) > return -EEXIST; > > + ret = hv_call_deposit_pages(NUMA_NO_NODE, partition->pt_id, > + MSHV_VP_DEPOSIT_PAGES); > + if (ret) > + return ret; > + > ret = hv_call_create_vp(NUMA_NO_NODE, partition->pt_id, args.vp_index, > 0 /* Only valid for root partition VPs */); > if (ret) > - return ret; > + goto withdraw_mem; > > ret = hv_map_vp_state_page(partition->pt_id, args.vp_index, > HV_VP_STATE_PAGE_INTERCEPT_MESSAGE, > @@ -1177,6 +1183,9 @@ mshv_partition_ioctl_create_vp(struct mshv_partition > *partition, > intercept_msg_page, input_vtl_zero); > destroy_vp: > hv_call_delete_vp(partition->pt_id, args.vp_index); > +withdraw_mem: > + hv_call_withdraw_memory(MSHV_VP_DEPOSIT_PAGES, NUMA_NO_NODE, > + partition->pt_id);
If the partition is an L1VH partition, hv_call_deposit_pages() will have deposited 2 * MSHV_VP_DEPOSIT_PAGES, but here in the failure case you are withdrawing only MSHV_VP_DEPOSIT_PAGES. > out: > trace_mshv_create_vp(partition->pt_id, args.vp_index, ret); > return ret; > >
