Re: [PATCH 3/7] x86/hyperv: Use hv_hvcall_*() to set up hypercall arguments -- part 1

Nuno Das Neves
2025-02-27T21:07:55Z

On 2/26/2025 12:06 PM, mhkelley58@gmail.com wrote:
> From: Michael Kelley <mhklinux@outlook.com>
>
> Update hypercall call sites to use the new hv_hvcall_*() functions
> to set up hypercall arguments. Since these functions zero the
> fixed portion of input memory, remove now redundant calls to memset()
> and explicit zero'ing of input fields.
>
> Signed-off-by: Michael Kelley <mhklinux@outlook.com>
> ---
> arch/x86/hyperv/hv_apic.c | 6 ++----
> arch/x86/hyperv/hv_init.c | 5 +----
> arch/x86/hyperv/hv_vtl.c | 8 ++------
> arch/x86/hyperv/irqdomain.c | 10 ++++------
> 4 files changed, 9 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index f022d5f64fb6..c16f81dd36fc 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -115,14 +115,12 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector,
> return false;
>
> local_irq_save(flags);
> - ipi_arg = *this_cpu_ptr(hyperv_pcpu_input_arg);
> -
> + hv_hvcall_in_array(&ipi_arg, sizeof(*ipi_arg),
> + sizeof(ipi_arg->vp_set.bank_contents[0]));
I think the returned "batch size" should be checked to ensure it is not too small to hold the
variable-sized part of the header.

> if (unlikely(!ipi_arg))
> goto ipi_mask_ex_done;
>
While here, is this check really needed? If so, maybe a check for the percpu page(s) could be
baked into hv_hvcall_inout_array()?

> ipi_arg->vector = vector;
> - ipi_arg->reserved = 0;
> - ipi_arg->vp_set.valid_bank_mask = 0;
>
> /*
> * Use HV_GENERIC_SET_ALL and avoid converting cpumask to VP_SET
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index ddeb40930bc8..c5c9511cb7ed 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -400,13 +400,10 @@ static u8 __init get_vtl(void)
> u64 ret;
>
> local_irq_save(flags);
> - input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> - output = *this_cpu_ptr(hyperv_pcpu_output_arg);
>
> - memset(input, 0, struct_size(input, names, 1));
> + hv_hvcall_inout(&input, sizeof(*input), &output, sizeof(*output));

This doesn't look right, this is a rep hypercall taking an array of register names
and outputting an array of register values.

hv_hvcall_inout_array() should be fully utilized (input and output arrays) here.

The current code may actually work, but it will overlap the input and output!

> input->partition_id = HV_PARTITION_ID_SELF;
> input->vp_index = HV_VP_INDEX_SELF;
> - input->input_vtl.as_uint8 = 0;
> input->names[0] = HV_REGISTER_VSM_VP_STATUS;
>
> ret = hv_do_hypercall(control, input, output);
> diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
> index 3f4e20d7b724..3dd27d548db6 100644
> --- a/arch/x86/hyperv/hv_vtl.c
> +++ b/arch/x86/hyperv/hv_vtl.c
<snip>
> @@ -185,13 +184,10 @@ static int hv_vtl_apicid_to_vp_id(u32 apic_id)
>
> local_irq_save(irq_flags);
>
> - input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> - memset(input, 0, sizeof(*input));
> + hv_hvcall_inout(&input, sizeof(*input), &output, sizeof(*output));
This has the same issue as above - it is a rep hypercall so needs hv_hvcall_inout_array()

> input->partition_id = HV_PARTITION_ID_SELF;
> input->apic_ids[0] = apic_id;
>
> - output = *this_cpu_ptr(hyperv_pcpu_output_arg);
> -
> control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID;
> status = hv_do_hypercall(control, input, output);
> ret = output[0];
> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> index 64b921360b0f..803b1a945c5c 100644
> --- a/arch/x86/hyperv/irqdomain.c
> +++ b/arch/x86/hyperv/irqdomain.c
> @@ -24,11 +24,11 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
>
> local_irq_save(flags);
>
> - input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> - output = *this_cpu_ptr(hyperv_pcpu_output_arg);
> + hv_hvcall_inout_array(&input, sizeof(*input),
> + sizeof(input->interrupt_descriptor.target.vp_set.bank_contents[0]),
> + &output, sizeof(*output), 0);
As noted before I think the batch size should be checked to ensure it is large enough.

Side note - it seems in this hypercall, nr_banks + 1 is used as the varhead size, which
counts the vp valid mask, but this is not the case in __send_ipi_mask_ex(). Do you happen
to know why that might be?

Thanks,
Nuno

>
> intr_desc = &input->interrupt_descriptor;
> - memset(input, 0, sizeof(*input));
> input->partition_id = hv_current_partition_id;
> input->device_id = device_id.as_uint64;
> intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
<snip>