On 2/11/2025 9:47 PM, Easwar Hariharan wrote: > On 2/11/2025 2:21 PM, Nuno Das Neves wrote: >> Introduce CONFIG_MSHV_ROOT as a tristate to enable root partition >> booting and future mshv driver functionality. >> >> Change hv_root_partition into a function which always returns false >> if CONFIG_MSHV_ROOT=n. >> >> Introduce hv_current_partition_type to store the type of partition >> (guest, root, or other kinds in future), and hv_identify_partition_type() >> to it up early in Hyper-V initialization. > > ...to *set* it up early? > Yep! Thanks for catching that >> >> Signed-off-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> >> --- >> Depends on >> https://lore.kernel.org/linux-hyperv/1738955002-20821-3-git-send-email-nunodasneves@xxxxxxxxxxxxxxxxxxx/ >> >> arch/arm64/hyperv/mshyperv.c | 2 ++ >> arch/x86/hyperv/hv_init.c | 10 ++++---- >> arch/x86/kernel/cpu/mshyperv.c | 24 ++---------------- >> drivers/clocksource/hyperv_timer.c | 4 +-- >> drivers/hv/Kconfig | 12 +++++++++ >> drivers/hv/Makefile | 3 ++- >> drivers/hv/hv.c | 10 ++++---- >> drivers/hv/hv_common.c | 32 +++++++++++++++++++----- >> drivers/hv/vmbus_drv.c | 2 +- >> drivers/iommu/hyperv-iommu.c | 4 +-- >> include/asm-generic/mshyperv.h | 39 +++++++++++++++++++++++++----- >> 11 files changed, 92 insertions(+), 50 deletions(-) >> > > <snip> > >> + >> +void hv_identify_partition_type(void) >> +{ >> + /* >> + * Check partition creation and cpu management privileges >> + * >> + * Hyper-V should never specify running as root and as a Confidential >> + * VM. But to protect against a compromised/malicious Hyper-V trying >> + * to exploit root behavior to expose Confidential VM memory, ignore >> + * the root partition setting if also a Confidential VM. >> + */ >> + if ((ms_hyperv.priv_high & HV_CREATE_PARTITIONS) && >> + (ms_hyperv.priv_high & HV_CPU_MANAGEMENT) && >> + !(ms_hyperv.priv_high & HV_ISOLATION)) { >> + hv_current_partition_type = HV_PARTITION_TYPE_ROOT; >> + pr_info("Hyper-V: running as root partition\n"); >> + } else { >> + hv_current_partition_type = HV_PARTITION_TYPE_GUEST; >> + } >> +} > > This should assume GUEST as default and modify to ROOT if all the checks pass. > It is doing that, isn't it? In fact the 'else' branch here is redundant and just there for additional clarity. hv_current_partition_type is zeroed (so GUEST) by default, but I could make that explicit if you prefer: +enum hv_partition_type hv_current_partition_type = HV_PARTITION_TYPE_GUEST; How does that sound? Am I misunderstanding something here? > <snip> > >> +static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages) >> +{ >> + return hv_result(U64_MAX); >> +} > > Is there value in perhaps #defining hv_result_<whatever this is> as U64_MAX and returning that for documentation? > For e.g. assuming this is something like EOPNOTSUPP > > #define HV_RESULT_NOT_SUPP U64_MAX > > static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages) > { return hv_result(HV_RESULT_NOT_SUPP); } > The idea here was to copy what hv_do_hypercall does returning U64_MAX in case the hypercall page is missing, which will hv_result() into an invalid status code. A special value for that status could make this pattern clearer. I'd want to call out that this isn't a "real" Hyper-V status code somehow. HV_STATUS's are 16 bits, so it would look more like: /* "LINUX" because this isn't really a status from the hypervisor.. */ #define HV_STATUS_LINUX_FAIL 0xFFFF static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages) { return HV_STATUS_LINUX_FAIL; } Another option: there is another patch coming (which you know of) which maps hypercall status codes to regular Linux errors like -EOPNOTSUPP. I could simply merge that patch with this one (or make this a series for v2), and that would result in less churn. (And leave alone the current use of U64_MAX in hv_do_hypercall, for now). Nuno > <snip> > > Thanks, > Easwar (he/him)
