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Message-ID:
<SN6PR02MB415781A21E3F8CF52AB2A579D41BA@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Mon, 29 Sep 2025 17:55:57 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"prapal@...ux.microsoft.com" <prapal@...ux.microsoft.com>,
"easwar.hariharan@...ux.microsoft.com"
<easwar.hariharan@...ux.microsoft.com>, "tiala@...rosoft.com"
<tiala@...rosoft.com>, "anirudh@...rudhrb.com" <anirudh@...rudhrb.com>,
"paekkaladevi@...ux.microsoft.com" <paekkaladevi@...ux.microsoft.com>,
"skinsburskii@...ux.microsoft.com" <skinsburskii@...ux.microsoft.com>
CC: "kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com"
<haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
"decui@...rosoft.com" <decui@...rosoft.com>
Subject: RE: [PATCH v4 2/5] mshv: Add the HVCALL_GET_PARTITION_PROPERTY_EX
hypercall
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Friday, September 26, 2025 9:23 AM
>
> From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@...ux.microsoft.com>
>
> This hypercall can be used to fetch extended properties of a
> partition. Extended properties are properties with values larger than
> a u64. Some of these also need additional input arguments.
>
> Add helper function for using the hypercall in the mshv_root driver.
>
> Signed-off-by: Purna Pavan Chandra Aekkaladevi <paekkaladevi@...ux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> Reviewed-by: Anirudh Rayabharam <anirudh@...rudhrb.com>
> Reviewed-by: Praveen K Paladugu <prapal@...ux.microsoft.com>
> Reviewed-by: Easwar Hariharan <easwar.hariharan@...ux.microsoft.com>
> ---
> drivers/hv/mshv_root.h | 2 ++
> drivers/hv/mshv_root_hv_call.c | 31 ++++++++++++++++++++++++++
> include/hyperv/hvgdk_mini.h | 1 +
> include/hyperv/hvhdk.h | 40 ++++++++++++++++++++++++++++++++++
> include/hyperv/hvhdk_mini.h | 26 ++++++++++++++++++++++
> 5 files changed, 100 insertions(+)
>
> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
> index e3931b0f1269..4aeb03bea6b6 100644
> --- a/drivers/hv/mshv_root.h
> +++ b/drivers/hv/mshv_root.h
> @@ -303,6 +303,8 @@ int hv_call_unmap_stat_page(enum hv_stats_object_type type,
> int hv_call_modify_spa_host_access(u64 partition_id, struct page **pages,
> u64 page_struct_count, u32 host_access,
> u32 flags, u8 acquire);
> +int hv_call_get_partition_property_ex(u64 partition_id, u64 property_code, u64 arg,
> + void *property_value, size_t property_value_sz);
>
> extern struct mshv_root mshv_root;
> extern enum hv_scheduler_type hv_scheduler_type;
> diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
> index c9c274f29c3c..3fd3cce23f69 100644
> --- a/drivers/hv/mshv_root_hv_call.c
> +++ b/drivers/hv/mshv_root_hv_call.c
> @@ -590,6 +590,37 @@ int hv_call_unmap_vp_state_page(u64 partition_id, u32 vp_index, u32 type,
> return hv_result_to_errno(status);
> }
>
> +int hv_call_get_partition_property_ex(u64 partition_id, u64 property_code,
> + u64 arg, void *property_value,
> + size_t property_value_sz)
> +{
> + u64 status;
> + unsigned long flags;
> + struct hv_input_get_partition_property_ex *input;
> + struct hv_output_get_partition_property_ex *output;
> +
> + local_irq_save(flags);
> + input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> + output = *this_cpu_ptr(hyperv_pcpu_output_arg);
> +
> + memset(input, 0, sizeof(*input));
> + input->partition_id = partition_id;
> + input->property_code = property_code;
> + input->arg = arg;
> + status = hv_do_hypercall(HVCALL_GET_PARTITION_PROPERTY_EX, input, output);
> +
> + if (!hv_result_success(status)) {
> + hv_status_debug(status, "\n");
> + local_irq_restore(flags);
Nit: It would be marginally better to do the local_irq_restore() first, and then
output the error message so that interrupts are not disabled any longer than
needed.
> + return hv_result_to_errno(status);
> + }
> + memcpy(property_value, &output->property_value, property_value_sz);
> +
> + local_irq_restore(flags);
> +
> + return 0;
> +}
> +
> int
> hv_call_clear_virtual_interrupt(u64 partition_id)
> {
> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> index 1be7f6a02304..ff4325fb623a 100644
> --- a/include/hyperv/hvgdk_mini.h
> +++ b/include/hyperv/hvgdk_mini.h
> @@ -490,6 +490,7 @@ union hv_vp_assist_msr_contents { /*
> HV_REGISTER_VP_ASSIST_PAGE */
> #define HVCALL_GET_VP_STATE 0x00e3
> #define HVCALL_SET_VP_STATE 0x00e4
> #define HVCALL_GET_VP_CPUID_VALUES 0x00f4
> +#define HVCALL_GET_PARTITION_PROPERTY_EX 0x0101
> #define HVCALL_MMIO_READ 0x0106
> #define HVCALL_MMIO_WRITE 0x0107
>
> diff --git a/include/hyperv/hvhdk.h b/include/hyperv/hvhdk.h
> index b4067ada02cf..416c0d45b793 100644
> --- a/include/hyperv/hvhdk.h
> +++ b/include/hyperv/hvhdk.h
> @@ -376,6 +376,46 @@ struct hv_input_set_partition_property {
> u64 property_value;
> } __packed;
>
> +union hv_partition_property_arg {
> + u64 as_uint64;
> + struct {
> + union {
> + u32 arg;
> + u32 vp_index;
> + };
> + u16 reserved0;
> + u8 reserved1;
> + u8 object_type;
> + } __packed;
> +};
> +
> +struct hv_input_get_partition_property_ex {
> + u64 partition_id;
> + u32 property_code; /* enum hv_partition_property_code */
> + u32 padding;
> + union {
> + union hv_partition_property_arg arg_data;
> + u64 arg;
This union, and the "u64 arg" member, seems redundant since
union hv_partition_property_arg already has a member "as_uint64".
Maybe this is just being copied from the Windows versions of these
structures, in which case I realize there are constraints on what you
want to change or fix, and you can ignore my comment.
> + };
> +} __packed;
> +
> +/*
> + * NOTE: Should use hv_input_set_partition_property_ex_header to compute this
> + * size, but hv_input_get_partition_property_ex is identical so it suffices
> + */
> +#define HV_PARTITION_PROPERTY_EX_MAX_VAR_SIZE \
> + (HV_HYP_PAGE_SIZE - sizeof(struct hv_input_get_partition_property_ex))
> +
> +union hv_partition_property_ex {
> + u8 buffer[HV_PARTITION_PROPERTY_EX_MAX_VAR_SIZE];
It's unclear what this "buffer" field is trying to do, and particularly its size.
The comment above references hv_input_set_partition_property_ex_header,
which doesn't exist in the Linux code. And why is the max size of the output
buffer reduced by the size of the header of the input to "set partition property"?
> + struct hv_partition_property_vmm_capabilities vmm_capabilities;
> + /* More fields to be filled in when needed */
> +};
> +
> +struct hv_output_get_partition_property_ex {
> + union hv_partition_property_ex property_value;
> +} __packed;
> +
> enum hv_vp_state_page_type {
> HV_VP_STATE_PAGE_REGISTERS = 0,
> HV_VP_STATE_PAGE_INTERCEPT_MESSAGE = 1,
> diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
> index 858f6a3925b3..bf2ce27dfcc5 100644
> --- a/include/hyperv/hvhdk_mini.h
> +++ b/include/hyperv/hvhdk_mini.h
> @@ -96,8 +96,34 @@ enum hv_partition_property_code {
> HV_PARTITION_PROPERTY_XSAVE_STATES = 0x00060007,
> HV_PARTITION_PROPERTY_MAX_XSAVE_DATA_SIZE = 0x00060008,
> HV_PARTITION_PROPERTY_PROCESSOR_CLOCK_FREQUENCY = 0x00060009,
> +
> + /* Extended properties with larger property values */
> + HV_PARTITION_PROPERTY_VMM_CAPABILITIES = 0x00090007,
> };
>
> +#define HV_PARTITION_VMM_CAPABILITIES_BANK_COUNT 1
> +#define HV_PARTITION_VMM_CAPABILITIES_RESERVED_BITFIELD_COUNT 59
> +
> +struct hv_partition_property_vmm_capabilities {
> + u16 bank_count;
> + u16 reserved[3];
> + union {
> + u64 as_uint64[HV_PARTITION_VMM_CAPABILITIES_BANK_COUNT];
> + struct {
> + u64 map_gpa_preserve_adjustable: 1;
> + u64 vmm_can_provide_overlay_gpfn: 1;
> + u64 vp_affinity_property: 1;
> +#if IS_ENABLED(CONFIG_ARM64)
> + u64 vmm_can_provide_gic_overlay_locations: 1;
> +#else
> + u64 reservedbit3: 1;
> +#endif
> + u64 assignable_synthetic_proc_features: 1;
> + u64 reserved0: HV_PARTITION_VMM_CAPABILITIES_RESERVED_BITFIELD_COUNT;
> + } __packed;
> + };
> +} __packed;
> +
> enum hv_snp_status {
> HV_SNP_STATUS_NONE = 0,
> HV_SNP_STATUS_AVAILABLE = 1,
> --
> 2.34.1
>
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