arch/x86/hyperv/hv_init.c | 6 +++--- arch/x86/hyperv/hv_vtl.c | 2 +- drivers/hv/hv_common.c | 11 +++++++--- include/hyperv/hvgdk_mini.h | 41 +++++++++++++++++++++++++++++++++++++ 4 files changed, 53 insertions(+), 7 deletions(-)
The get_vtl(void) function
* has got one bug when the code started using a wrong pointer type after
refactoring, and also
* the both function in question don't adhere to the requirements of
the Hypervisor Top-Level Funactional Specification[1, 2] as the code overlaps
the input and output areas for a hypercall.
The first issue leads to a wrong 100% reproducible computation due to reading
a byte worth of data at a wrong offset. That in turn leads to using a nonsensical
value ("fortunately", could catch it easily!) for the current VTL when initiating
VMBus communications. As a repercussion from that, the system wouldn't boot. The
fix is straightforward: use the correct pointer type.
The second issue doesn't seem to lead to any reproducible breakage just yet. It is
fixed with using the output hypercall pages allocated per-CPU, and that isn't the
only or the most obvious choice so let me elaborate why that fix appears to be the
best one in my opinion out of the options I could conceive of.
The approach chosen for fixing the second issue makes two things shine through:
* these functions just get a vCPU register, no special treatment needs to be
involved,
* VTLs and dom0 can and should share code as both exist to provide services to
a guest(s), be that from within the partition or from outside of it.
The projected benefits include replacing the functions in question with a future
`hv_get_vp_registers` one shared between dom0 and VTLs to allow for a better test
coverage.
I have validated the fixes by booting the fixed kernel in VTL2 up using OpenVMM and
OpenHCL[3, 4].
[1] https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/hypercall-interface
[2] https://github.com/MicrosoftDocs/Virtualization-Documentation/tree/main/tlfs
[3] https://openvmm.dev/guide/user_guide/openhcl.html
[4] https://github.com/microsoft/OpenVMM
[v6]
- Sending v6 a week after v5 to adhere to the requirements of the kernel
documentation,
- Added all tags the patches received prior to v6,
- Fixed the bitfield layout for the ARM64 structures (patch 1),
- Hoisted the common condition used in several if statements into
a separate function to improve code maintainability (patch 3).
[v5]: https://lore.kernel.org/lkml/20241230180941.244418-1-romank@linux.microsoft.com/
- In the first patch, removed some arch-specific #ifdef guards to fix the
arm64 build and stick to the direction chosen for the Hyper-V header files.
I could not remove all of them as some interrupt state structures
are defined differently for x64 and arm64 and are found in the same
enclosing `union hv_register_value`.
No changes to other patches (approved in v4).
[v4]: https://lore.kernel.org/lkml/20241227183155.122827-1-romank@linux.microsoft.com/
- Wrapped DECLARE_FLEX_ARRAY into a struct and added one more
member as the documentation requires,
- Removed superfluous type coercion,
- Fixed tags,
- Rebased onto the latest hyperv-next branch.
[v3]: https://lore.kernel.org/lkml/20241226213110.899497-1-romank@linux.microsoft.com/
- Added a fix for hv_vtl_apicid_to_vp_id(),
- Split out the patch for enabling the hypercall output page,
- Updated the title of the patch series,
[v2]: https://lore.kernel.org/lkml/20241226203050.800524-1-romank@linux.microsoft.com/
- Used the suggestions to define an additional structure to improve code readability,
- Split out the patch with that definition.
[v1]: https://lore.kernel.org/lkml/20241218205421.319969-1-romank@linux.microsoft.com/
Roman Kisel (5):
hyperv: Define struct hv_output_get_vp_registers
hyperv: Fix pointer type in get_vtl(void)
hyperv: Enable the hypercall output page for the VTL mode
hyperv: Do not overlap the hvcall IO areas in get_vtl()
hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()
arch/x86/hyperv/hv_init.c | 6 +++---
arch/x86/hyperv/hv_vtl.c | 2 +-
drivers/hv/hv_common.c | 11 +++++++---
include/hyperv/hvgdk_mini.h | 41 +++++++++++++++++++++++++++++++++++++
4 files changed, 53 insertions(+), 7 deletions(-)
base-commit: 26e1b813fcd02984b1cac5f3decdf4b0bb56fe02
--
2.34.1
On Wed, Jan 08, 2025 at 02:21:33PM -0800, Roman Kisel wrote: [...] > Roman Kisel (5): > hyperv: Define struct hv_output_get_vp_registers > hyperv: Fix pointer type in get_vtl(void) > hyperv: Enable the hypercall output page for the VTL mode > hyperv: Do not overlap the hvcall IO areas in get_vtl() > hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id() The patches have been pushed to hyperv-next. Roman and Nuno, please check the tree for correctness. Thanks, Wei.
On 1/9/2025 12:18 PM, Wei Liu wrote:
> On Wed, Jan 08, 2025 at 02:21:33PM -0800, Roman Kisel wrote:
> [...]
>> Roman Kisel (5):
>> hyperv: Define struct hv_output_get_vp_registers
>> hyperv: Fix pointer type in get_vtl(void)
>> hyperv: Enable the hypercall output page for the VTL mode
>> hyperv: Do not overlap the hvcall IO areas in get_vtl()
>> hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()
>
> The patches have been pushed to hyperv-next. Roman and Nuno, please
> check the tree for correctness.
This
```c
union hv_arm64_pending_synthetic_exception_event {
u64 as_uint64[2];
struct {
u8 event_pending : 1;
u8 event_type : 3;
u8 reserved : 4;
u8 rsvd[3];
u64 context;
} __packed;
};
```
needs to have the `u32 exception_type;` field:
```c
union hv_arm64_pending_synthetic_exception_event {
u64 as_uint64[2];
struct {
u8 event_pending : 1;
u8 event_type : 3;
u8 reserved : 4;
u8 rsvd[3];
u32 exception_type;
u64 context;
} __packed;
};
```
as otherwise the struct won't cover the array.
Testing the VMs currently with the latest hyperv-next.
>
> Thanks,
> Wei.
--
Thank you,
Roman
On Thu, Jan 09, 2025 at 01:40:34PM -0800, Roman Kisel wrote:
>
>
> On 1/9/2025 12:18 PM, Wei Liu wrote:
> > On Wed, Jan 08, 2025 at 02:21:33PM -0800, Roman Kisel wrote:
> > [...]
> > > Roman Kisel (5):
> > > hyperv: Define struct hv_output_get_vp_registers
> > > hyperv: Fix pointer type in get_vtl(void)
> > > hyperv: Enable the hypercall output page for the VTL mode
> > > hyperv: Do not overlap the hvcall IO areas in get_vtl()
> > > hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()
> >
> > The patches have been pushed to hyperv-next. Roman and Nuno, please
> > check the tree for correctness.
>
> This
>
> ```c
> union hv_arm64_pending_synthetic_exception_event {
> u64 as_uint64[2];
> struct {
> u8 event_pending : 1;
> u8 event_type : 3;
> u8 reserved : 4;
> u8 rsvd[3];
> u64 context;
> } __packed;
> };
> ```
>
> needs to have the `u32 exception_type;` field:
>
> ```c
> union hv_arm64_pending_synthetic_exception_event {
> u64 as_uint64[2];
> struct {
> u8 event_pending : 1;
> u8 event_type : 3;
> u8 reserved : 4;
> u8 rsvd[3];
> u32 exception_type;
> u64 context;
> } __packed;
> };
> ```
> as otherwise the struct won't cover the array.
> Testing the VMs currently with the latest hyperv-next.
Fixed. I c&p'ed the code then deleted the right version of the struct.
Thanks for checking.
Wei.
On 1/9/2025 1:56 PM, Wei Liu wrote:
> On Thu, Jan 09, 2025 at 01:40:34PM -0800, Roman Kisel wrote:
[...]
>>
>> needs to have the `u32 exception_type;` field:
>>
>> ```c
>> union hv_arm64_pending_synthetic_exception_event {
>> u64 as_uint64[2];
>> struct {
>> u8 event_pending : 1;
>> u8 event_type : 3;
>> u8 reserved : 4;
>> u8 rsvd[3];
>> u32 exception_type;
>> u64 context;
>> } __packed;
>> };
>> ```
>> as otherwise the struct won't cover the array.
>> Testing the VMs currently with the latest hyperv-next.
>
> Fixed. I c&p'ed the code then deleted the right version of the struct.
> Thanks for checking.
Happy to help :D
Validated with the VMs, and with the latest hyperv-next, the issue is
fixed!! Appreciate your help and guidance; thank you, Easwar, Michael,
Nuno, Stanislav, Tianyu and Wei for the suggestions that have let make
this patchset so much better :)
Borislav, I apologize for sending the patchset versions too often. I'm
sorry for causing you trouble due to that. I have read up the kernel
documentation, and will be a better citizen of the LKML.
>
> Wei.
--
Thank you,
Roman
On 1/9/2025 12:18 PM, Wei Liu wrote: > On Wed, Jan 08, 2025 at 02:21:33PM -0800, Roman Kisel wrote: > [...] >> Roman Kisel (5): >> hyperv: Define struct hv_output_get_vp_registers >> hyperv: Fix pointer type in get_vtl(void) >> hyperv: Enable the hypercall output page for the VTL mode >> hyperv: Do not overlap the hvcall IO areas in get_vtl() >> hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id() > > The patches have been pushed to hyperv-next. Roman and Nuno, please > check the tree for correctness. > > Thanks, > Wei. I checked, looks like the first two patches of the series are missing? Nuno
On 1/9/2025 12:28 PM, Nuno Das Neves wrote: > On 1/9/2025 12:18 PM, Wei Liu wrote: >> On Wed, Jan 08, 2025 at 02:21:33PM -0800, Roman Kisel wrote: >> [...] >>> Roman Kisel (5): >>> hyperv: Define struct hv_output_get_vp_registers >>> hyperv: Fix pointer type in get_vtl(void) >>> hyperv: Enable the hypercall output page for the VTL mode >>> hyperv: Do not overlap the hvcall IO areas in get_vtl() >>> hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id() >> >> The patches have been pushed to hyperv-next. Roman and Nuno, please >> check the tree for correctness. >> >> Thanks, >> Wei. > > I checked, looks like the first two patches of the series are missing? IIUC, they were to be rolled up into your earlier patches > > Nuno -- Thank you, Roman
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