On 9/5/2025 12:03 PM, Anirudh Rayabharam wrote: > On Thu, Aug 28, 2025 at 05:43:48PM -0700, Nuno Das Neves wrote: >> From: Purna Pavan Chandra Aekkaladevi <[email protected]> >> >> Some newer hypervisor APIs are gated by feature bits in the so-called >> "vmm capabilities" partition property. Store the capabilities on >> mshv_root module init, using HVCALL_GET_PARTITION_PROPERTY_EX. >> >> Signed-off-by: Purna Pavan Chandra Aekkaladevi >> <[email protected]> >> Signed-off-by: Nuno Das Neves <[email protected]> >> --- >> drivers/hv/mshv_root.h | 1 + >> drivers/hv/mshv_root_main.c | 28 ++++++++++++++++++++++++++++ >> 2 files changed, 29 insertions(+) >> >> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h >> index 4aeb03bea6b6..0cb1e2589fe1 100644 >> --- a/drivers/hv/mshv_root.h >> +++ b/drivers/hv/mshv_root.h >> @@ -178,6 +178,7 @@ struct mshv_root { >> struct hv_synic_pages __percpu *synic_pages; >> spinlock_t pt_ht_lock; >> DECLARE_HASHTABLE(pt_htable, MSHV_PARTITIONS_HASH_BITS); >> + struct hv_partition_property_vmm_capabilities vmm_caps; >> }; >> >> /* >> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c >> index 56ababab57ce..29f61ecc9771 100644 >> --- a/drivers/hv/mshv_root_main.c >> +++ b/drivers/hv/mshv_root_main.c >> @@ -2327,6 +2327,28 @@ static int __init mshv_root_partition_init(struct >> device *dev) >> return err; >> } >> >> +static int mshv_init_vmm_caps(struct device *dev) >> +{ >> + int ret; >> + >> + memset(&mshv_root.vmm_caps, 0, sizeof(mshv_root.vmm_caps)); >> + ret = hv_call_get_partition_property_ex(HV_PARTITION_ID_SELF, >> + >> HV_PARTITION_PROPERTY_VMM_CAPABILITIES, >> + 0, &mshv_root.vmm_caps, >> + sizeof(mshv_root.vmm_caps)); >> + >> + /* >> + * HV_PARTITION_PROPERTY_VMM_CAPABILITIES is not supported in >> + * older hyperv. Ignore the -EIO error code. >> + */ >> + if (ret && ret != -EIO) >> + return ret; >> + >> + dev_dbg(dev, "vmm_caps=0x%llx\n", mshv_root.vmm_caps.as_uint64[0]); >> + >> + return 0; >> +} >> + >> static int __init mshv_parent_partition_init(void) >> { >> int ret; >> @@ -2377,6 +2399,12 @@ static int __init mshv_parent_partition_init(void) >> if (ret) >> goto remove_cpu_state; >> >> + ret = mshv_init_vmm_caps(dev); >> + if (ret) { >> + dev_err(dev, "Failed to get VMM capabilities\n"); >> + goto exit_partition; > > Should this really be treated as a failure here? We could still offer > /dev/mshv albeit with potentially limited capabilities. >
I agree. It can continue with vmm_caps set to zero, and print an error. The check for -EIO is meant to achieve something similar but it's kind of unreliable since so many HV_STATUS's map to EIO. So this idea is better, thanks. Nuno > Thanks, > Anirudh. > >> + } >> + >> ret = mshv_irqfd_wq_init(); >> if (ret) >> goto exit_partition; >> -- >> 2.34.1 >>
