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Message-ID: <c7972607-7d99-5dad-354d-6ca8e8be0d8a@linux.microsoft.com>
Date: Mon, 8 Mar 2021 17:39:28 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Michael Kelley <mikelley@...rosoft.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Cc: "virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"viremana@...ux.microsoft.com" <viremana@...ux.microsoft.com>,
Sunil Muthuswamy <sunilmut@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
Lillian Grassin-Drake <Lillian.GrassinDrake@...rosoft.com>,
KY Srinivasan <kys@...rosoft.com>
Subject: Re: [RFC PATCH 10/18] virt/mshv: get and set vcpu registers ioctls
On 2/8/2021 11:47 AM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Friday, November 20, 2020 4:30 PM
>>
>> Add ioctls for getting and setting virtual processor registers.
>>
>> Co-developed-by: Lillian Grassin-Drake <ligrassi@...rosoft.com>
>> Signed-off-by: Lillian Grassin-Drake <ligrassi@...rosoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
>> ---
>> Documentation/virt/mshv/api.rst | 11 +
>> arch/x86/include/uapi/asm/hyperv-tlfs.h | 601 ++++++++++++++++++++++++
>> include/asm-generic/hyperv-tlfs.h | 65 +--
>> include/linux/mshv.h | 1 +
>> include/uapi/linux/mshv.h | 12 +
>> virt/mshv/mshv_main.c | 258 +++++++++-
>> 6 files changed, 903 insertions(+), 45 deletions(-)
>>
[snip]
>> +
>> +union hv_register_value {
>> + struct hv_u128 reg128;
>> + __u64 reg64;
>> + __u32 reg32;
>> + __u16 reg16;
>> + __u8 reg8;
>> + union hv_x64_fp_register fp;
>> + union hv_x64_fp_control_status_register fp_control_status;
>> + union hv_x64_xmm_control_status_register xmm_control_status;
>> + struct hv_x64_segment_register segment;
>> + struct hv_x64_table_register table;
>> + union hv_explicit_suspend_register explicit_suspend;
>> + union hv_intercept_suspend_register intercept_suspend;
>> + union hv_dispatch_suspend_register dispatch_suspend;
>> + union hv_x64_interrupt_state_register interrupt_state;
>> + union hv_x64_pending_interruption_register pending_interruption;
>> + union hv_x64_msr_npiep_config_contents npiep_config;
>> + union hv_x64_pending_exception_event pending_exception_event;
>> + union hv_x64_pending_virtualization_fault_event
>> + pending_virtualization_fault_event;
>> +};
>> +
>> #endif
>> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
>> index 6e5072e29897..b9295400c20b 100644
>> --- a/include/asm-generic/hyperv-tlfs.h
>> +++ b/include/asm-generic/hyperv-tlfs.h
>> @@ -622,53 +622,30 @@ struct hv_retarget_device_interrupt {
>> } __packed __aligned(8);
>>
>>
>> -/* HvGetVpRegisters hypercall input with variable size reg name list*/
>> -struct hv_get_vp_registers_input {
>> - struct {
>> - u64 partitionid;
>> - u32 vpindex;
>> - u8 inputvtl;
>> - u8 padding[3];
>> - } header;
>> - struct input {
>> - u32 name0;
>> - u32 name1;
>> - } element[];
>> -} __packed;
>> -
>> +/* HvGetVpRegisters hypercall with variable size reg name list*/
>> +struct hv_get_vp_registers {
>> + u64 partition_id;
>> + u32 vp_index;
>> + u8 input_vtl;
>> + u8 rsvd_z8;
>> + u16 rsvd_z16;
>> + __aligned(8) enum hv_register_name names[];
>> +} __aligned(8);
>>
>> -/* HvGetVpRegisters returns an array of these output elements */
>> -struct hv_get_vp_registers_output {
>> - union {
>> - struct {
>> - u32 a;
>> - u32 b;
>> - u32 c;
>> - u32 d;
>> - } as32 __packed;
>> - struct {
>> - u64 low;
>> - u64 high;
>> - } as64 __packed;
>> - };
>> +/* HvSetVpRegisters hypercall with variable size reg name/value list*/
>> +struct hv_register_assoc {
>> + enum hv_register_name name;
>> + __aligned(16) union hv_register_value value;
>> };
>>
>> -/* HvSetVpRegisters hypercall with variable size reg name/value list*/
>> -struct hv_set_vp_registers_input {
>> - struct {
>> - u64 partitionid;
>> - u32 vpindex;
>> - u8 inputvtl;
>> - u8 padding[3];
>> - } header;
>> - struct {
>> - u32 name;
>> - u32 padding1;
>> - u64 padding2;
>> - u64 valuelow;
>> - u64 valuehigh;
>> - } element[];
>> -} __packed;
>> +struct hv_set_vp_registers {
>> + u64 partition_id;
>> + u32 vp_index;
>> + u8 input_vtl;
>> + u8 rsvd_z8;
>> + u16 rsvd_z16;
>> + struct hv_register_assoc elements[];
>> +} __aligned(16);
>
> Throughout these structures, I think the approach needs to be more
> explicit about the memory layout. The current definitions assume that
> the compiler is inserting padding in the expected places, and not in
> any unexpected places. My previous concerns about use of enum
> also apply.
>
> The code also removes some layouts that are used in the
> not-yet-accepted patches for ARM64. Let sync on how to get
> those back in.
>
I'll add __packed to all these structures.
The hv_register_name enum can be replaced by #defines, and the type can be
u32 or u64 (it only needs 32 bits).
I'll sync with you on the ARM64 structs.
>>
>> enum hv_device_type {
>> HV_DEVICE_TYPE_LOGICAL = 0,
>> diff --git a/include/linux/mshv.h b/include/linux/mshv.h
>> index 50521c5f7948..dfe469f573f9 100644
>> --- a/include/linux/mshv.h
>> +++ b/include/linux/mshv.h
>> @@ -17,6 +17,7 @@
>> struct mshv_vp {
>> u32 index;
>> struct mshv_partition *partition;
>> + struct mutex mutex;
>> };
>>
>> struct mshv_mem_region {
>> diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
>> index 1f053eae68a6..5d53ed655429 100644
>> --- a/include/uapi/linux/mshv.h
>> +++ b/include/uapi/linux/mshv.h
>> @@ -33,6 +33,14 @@ struct mshv_create_vp {
>> __u32 vp_index;
>> };
>>
>> +#define MSHV_VP_MAX_REGISTERS 128
>> +
>> +struct mshv_vp_registers {
>> + int count; /* at most MSHV_VP_MAX_REGISTERS */
>> + enum hv_register_name *names;
>> + union hv_register_value *values;
>> +};
>
> Having separate arrays for the names and values results in an extra
> copy of the data down in the ioctl code. Any reason the caller couldn't
> supply the data as an array, where each entry is already a name/value
> pair?
>
I initially thought it would not make a difference to the number of copies,
but it turns out it does. I will change it to use hv_register_assoc everywhere.
>> +
>> #define MSHV_IOCTL 0xB8
>>
>> /* mshv device */
>> @@ -44,4 +52,8 @@ struct mshv_create_vp {
>> #define MSHV_UNMAP_GUEST_MEMORY _IOW(MSHV_IOCTL, 0x03, struct
>> mshv_user_mem_region)
>> #define MSHV_CREATE_VP _IOW(MSHV_IOCTL, 0x04, struct mshv_create_vp)
>>
>> +/* vp device */
>> +#define MSHV_GET_VP_REGISTERS _IOWR(MSHV_IOCTL, 0x05, struct
>> mshv_vp_registers)
>> +#define MSHV_SET_VP_REGISTERS _IOW(MSHV_IOCTL, 0x06, struct mshv_vp_registers)
>> +
>> #endif
>> diff --git a/virt/mshv/mshv_main.c b/virt/mshv/mshv_main.c
>> index 3be9d9a468c1..2a10137a1e84 100644
>> --- a/virt/mshv/mshv_main.c
>> +++ b/virt/mshv/mshv_main.c
>> @@ -74,6 +74,12 @@ static struct miscdevice mshv_dev = {
>> #define HV_MAP_GPA_BATCH_SIZE \
>> (PAGE_SIZE / sizeof(struct hv_map_gpa_pages) / sizeof(u64))
>> #define PIN_PAGES_BATCH_SIZE (0x10000000 / PAGE_SIZE)
>> +#define HV_GET_REGISTER_BATCH_SIZE \
>> + (PAGE_SIZE / \
>> + sizeof(struct hv_get_vp_registers) / sizeof(enum hv_register_name))
>> +#define HV_SET_REGISTER_BATCH_SIZE \
>> + (PAGE_SIZE / \
>> + sizeof(struct hv_set_vp_registers) / sizeof(struct hv_register_assoc))
>
> These new size calculations have the same bug as HV_MAP_GPA_BATCH_SIZE.
> The first divide operations should be subtraction.
>
Yep, I'll fix it.
> With the correct calculation, HV_GET_REGISTER_BATCH_SIZE will be
> too large. The input page will accommodate more 32 bit register names
> than the output page will accommodate 128 bit register values. The limit
> should be based on the latter, not the former. Or calculate both the
> input and output limit and use the minimum.
>
I didn't think about this previously! Will fix.
>>
>> static int
>> hv_call_withdraw_memory(u64 count, int node, u64 partition_id)
>> @@ -380,10 +386,258 @@ hv_call_unmap_gpa_pages(u64 partition_id,
>> return ret;
>> }
>>
>> +static int
>> +hv_call_get_vp_registers(u32 vp_index,
>> + u64 partition_id,
>> + u16 count,
>> + const enum hv_register_name *names,
>> + union hv_register_value *values)
>> +{
>> + struct hv_get_vp_registers *input_page;
>> + union hv_register_value *output_page;
>> + u16 completed = 0;
>> + u64 hypercall_status;
>> + unsigned long remaining = count;
>> + int rep_count;
>> + int status;
>> + unsigned long flags;
>> +
>> + local_irq_save(flags);
>> +
>> + input_page = (struct hv_get_vp_registers *)(*this_cpu_ptr(
>> + hyperv_pcpu_input_arg));
>> + output_page = (union hv_register_value *)(*this_cpu_ptr(
>> + hyperv_pcpu_output_arg));
>> +
>> + input_page->partition_id = partition_id;
>> + input_page->vp_index = vp_index;
>> + input_page->input_vtl = 0;
>> + input_page->rsvd_z8 = 0;
>> + input_page->rsvd_z16 = 0;
>> +
>> + while (remaining) {
>> + rep_count = min(remaining, HV_GET_REGISTER_BATCH_SIZE);
>> + memcpy(input_page->names, names,
>> + sizeof(enum hv_register_name) * rep_count);
>> +
>> + hypercall_status =
>> + hv_do_rep_hypercall(HVCALL_GET_VP_REGISTERS, rep_count,
>> + 0, input_page, output_page);
>> + status = hypercall_status & HV_HYPERCALL_RESULT_MASK;
>> + if (status != HV_STATUS_SUCCESS) {
>> + pr_err("%s: completed %li out of %u, %s\n",
>> + __func__,
>> + count - remaining, count,
>> + hv_status_to_string(status));
>> + break;
>> + }
>> + completed = (hypercall_status & HV_HYPERCALL_REP_COMP_MASK) >>
>> + HV_HYPERCALL_REP_COMP_OFFSET;
>> + memcpy(values, output_page,
>> + sizeof(union hv_register_value) * completed);
>> +
>> + names += completed;
>> + values += completed;
>> + remaining -= completed;
>> + }
>> + local_irq_restore(flags);
>> +
>> + return -hv_status_to_errno(status);
>> +}
>> +
>> +static int
>> +hv_call_set_vp_registers(u32 vp_index,
>> + u64 partition_id,
>> + u16 count,
>> + struct hv_register_assoc *registers)
>> +{
>> + struct hv_set_vp_registers *input_page;
>> + u16 completed = 0;
>> + u64 hypercall_status;
>> + unsigned long remaining = count;
>> + int rep_count;
>> + int status;
>> + unsigned long flags;
>> +
>> + local_irq_save(flags);
>> + input_page = (struct hv_set_vp_registers *)(*this_cpu_ptr(
>> + hyperv_pcpu_input_arg));
>> +
>> + input_page->partition_id = partition_id;
>> + input_page->vp_index = vp_index;
>> + input_page->input_vtl = 0;
>> + input_page->rsvd_z8 = 0;
>> + input_page->rsvd_z16 = 0;
>> +
>> + while (remaining) {
>> + rep_count = min(remaining, HV_SET_REGISTER_BATCH_SIZE);
>> + memcpy(input_page->elements, registers,
>> + sizeof(struct hv_register_assoc) * rep_count);
>> +
>> + hypercall_status =
>> + hv_do_rep_hypercall(HVCALL_SET_VP_REGISTERS, rep_count,
>> + 0, input_page, NULL);
>> + status = hypercall_status & HV_HYPERCALL_RESULT_MASK;
>> + if (status != HV_STATUS_SUCCESS) {
>> + pr_err("%s: completed %li out of %u, %s\n",
>> + __func__,
>> + count - remaining, count,
>> + hv_status_to_string(status));
>> + break;
>> + }
>> + completed = (hypercall_status & HV_HYPERCALL_REP_COMP_MASK) >>
>> + HV_HYPERCALL_REP_COMP_OFFSET;
>> + registers += completed;
>> + remaining -= completed;
>> + }
>> +
>> + local_irq_restore(flags);
>> +
>> + return -hv_status_to_errno(status);
>> +}
>> +
>> +static long
>> +mshv_vp_ioctl_get_regs(struct mshv_vp *vp, void __user *user_args)
>> +{
>> + struct mshv_vp_registers args;
>> + enum hv_register_name *names;
>> + union hv_register_value *values;
>> + long ret;
>> +
>> + if (copy_from_user(&args, user_args, sizeof(args)))
>> + return -EFAULT;
>> +
>> + if (args.count > MSHV_VP_MAX_REGISTERS)
>> + return -EINVAL;
>> +
>> + names = kmalloc_array(args.count,
>> + sizeof(enum hv_register_name),
>> + GFP_KERNEL);
>> + if (!names)
>> + return -ENOMEM;
>> +
>> + values = kmalloc_array(args.count,
>> + sizeof(union hv_register_value),
>> + GFP_KERNEL);
>> + if (!values) {
>> + kfree(names);
>> + return -ENOMEM;
>> + }
>> +
>> + if (copy_from_user(names, args.names,
>> + sizeof(enum hv_register_name) * args.count)) {
>> + ret = -EFAULT;
>> + goto free_return;
>> + }
>> +
>> + ret = hv_call_get_vp_registers(vp->index, vp->partition->id,
>> + args.count, names, values);
>> + if (ret)
>> + goto free_return;
>> +
>> + if (copy_to_user(args.values, values,
>> + sizeof(union hv_register_value) * args.count)) {
>> + ret = -EFAULT;
>> + }
>> +
>> +free_return:
>> + kfree(names);
>> + kfree(values);
>> + return ret;
>> +}
>> +
>> +static long
>> +mshv_vp_ioctl_set_regs(struct mshv_vp *vp, void __user *user_args)
>> +{
>> + int i;
>> + struct mshv_vp_registers args;
>> + struct hv_register_assoc *registers;
>> + enum hv_register_name *names;
>> + union hv_register_value *values;
>> + long ret;
>> +
>> + if (copy_from_user(&args, user_args, sizeof(args)))
>> + return -EFAULT;
>> +
>> + if (args.count > MSHV_VP_MAX_REGISTERS)
>> + return -EINVAL;
>> +
>> + names = kmalloc_array(args.count,
>> + sizeof(enum hv_register_name),
>> + GFP_KERNEL);
>> + if (!names)
>> + return -ENOMEM;
>> +
>> + values = kmalloc_array(args.count,
>> + sizeof(union hv_register_value),
>> + GFP_KERNEL);
>> + if (!values) {
>> + kfree(names);
>> + return -ENOMEM;
>> + }
>> +
>> + registers = kmalloc_array(args.count,
>> + sizeof(struct hv_register_assoc),
>> + GFP_KERNEL);
>> + if (!registers) {
>> + kfree(values);
>> + kfree(names);
>> + return -ENOMEM;
>> + }
>> +
>> + if (copy_from_user(names, args.names,
>> + sizeof(enum hv_register_name) * args.count)) {
>> + ret = -EFAULT;
>> + goto free_return;
>> + }
>> +
>> + if (copy_from_user(values, args.values,
>> + sizeof(union hv_register_value) * args.count)) {
>> + ret = -EFAULT;
>> + goto free_return;
>> + }
>> +
>> + for (i = 0; i < args.count; i++) {
>> + memcpy(®isters[i].name, &names[i],
>> + sizeof(enum hv_register_name));
>> + memcpy(®isters[i].value, &values[i],
>> + sizeof(union hv_register_value));
>> + }
>
> The above will result in uninitialized memory being sent to
> Hyper-V, since there is implicit padding associated with the
> 32 bit name field.
>
This shouldn't be an issue after I change this to use hv_register_assoc,
instead of separate names and values buffers.
>> +
>> + ret = hv_call_set_vp_registers(vp->index, vp->partition->id,
>> + args.count, registers);
>> +
>> +free_return:
>> + kfree(names);
>> + kfree(values);
>> + kfree(registers);
>> + return ret;
>> +}
>> +
>> +
>> static long
>> mshv_vp_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
>> {
>> - return -ENOTTY;
>> + struct mshv_vp *vp = filp->private_data;
>> + long r = 0;
>> +
>> + if (mutex_lock_killable(&vp->mutex))
>> + return -EINTR;
>> +
>> + switch (ioctl) {
>> + case MSHV_GET_VP_REGISTERS:
>> + r = mshv_vp_ioctl_get_regs(vp, (void __user *)arg);
>> + break;
>> + case MSHV_SET_VP_REGISTERS:
>> + r = mshv_vp_ioctl_set_regs(vp, (void __user *)arg);
>> + break;
>> + default:
>> + r = -ENOTTY;
>> + break;
>> + }
>> + mutex_unlock(&vp->mutex);
>> +
>> + return r;
>> }
>>
>> static int
>> @@ -420,6 +674,8 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
>> if (!vp)
>> return -ENOMEM;
>>
>> + mutex_init(&vp->mutex);
>> +
>> vp->index = args.vp_index;
>> vp->partition = mshv_partition_get(partition);
>> if (!vp->partition) {
>> --
>> 2.25.1
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