Pull hyperv updates from Wei Liu:

 - Use Hyper-V entropy to seed guest random number generator (Michael
   Kelley)

 - Convert to platform remove callback returning void for vmbus (Uwe
   Kleine-König)

 - Introduce hv_get_hypervisor_version function (Nuno Das Neves)

 - Rename some HV_REGISTER_* defines for consistency (Nuno Das Neves)

 - Change prefix of generic HV_REGISTER_* MSRs to HV_MSR_* (Nuno Das
   Neves)

 - Cosmetic changes for hv_spinlock.c (Purna Pavan Chandra Aekkaladevi)

 - Use per cpu initial stack for vtl context (Saurabh Sengar)

* tag 'hyperv-next-signed-20240320' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux:
  x86/hyperv: Use Hyper-V entropy to seed guest random number generator
  x86/hyperv: Cosmetic changes for hv_spinlock.c
  hyperv-tlfs: Rename some HV_REGISTER_* defines for consistency
  hv: vmbus: Convert to platform remove callback returning void
  mshyperv: Introduce hv_get_hypervisor_version function
  x86/hyperv: Use per cpu initial stack for vtl context
  hyperv-tlfs: Change prefix of generic HV_REGISTER_* MSRs to HV_MSR_*

A Hyper-V host provides its guest VMs with entropy in a custom ACPI
table named "OEM0".  The entropy bits are updated each time Hyper-V
boots the VM, and are suitable for seeding the Linux guest random
number generator (rng). See a brief description of OEM0 in [1].

Generation 2 VMs on Hyper-V use UEFI to boot. Existing EFI code in
Linux seeds the rng with entropy bits from the EFI_RNG_PROTOCOL.
Via this path, the rng is seeded very early during boot with good
entropy. The ACPI OEM0 table provided in such VMs is an additional
source of entropy.

Generation 1 VMs on Hyper-V boot from BIOS. For these VMs, Linux
doesn't currently get any entropy from the Hyper-V host. While this
is not fundamentally broken because Linux can generate its own entropy,
using the Hyper-V host provided entropy would get the rng off to a
better start and would do so earlier in the boot process.

Improve the rng seeding for Generation 1 VMs by having Hyper-V specific
code in Linux take advantage of the OEM0 table to seed the rng. For
Generation 2 VMs, use the OEM0 table to provide additional entropy
beyond the EFI_RNG_PROTOCOL. Because the OEM0 table is custom to
Hyper-V, parse it directly in the Hyper-V code in the Linux kernel
and use add_bootloader_randomness() to add it to the rng. Once the
entropy bits are read from OEM0, zero them out in the table so
they don't appear in /sys/firmware/acpi/tables/OEM0 in the running
VM. The zero'ing is done out of an abundance of caution to avoid
potential security risks to the rng. Also set the OEM0 data length
to zero so a kexec or other subsequent use of the table won't try
to use the zero'ed bits.

[1] https://download.microsoft.com/download/1/c/9/1c9813b8-089c-4fef-b2ad-ad80e79403ba/Whitepaper%20-%20The%20Windows%2010%20random%20number%20generation%20infrastructure.pdf

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20240318155408.216851-1-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240318155408.216851-1-mhklinux@outlook.com>

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.

To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/920230729ddbeb9f3c4ff8282a18b0c0e1a37969.1709886922.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <920230729ddbeb9f3c4ff8282a18b0c0e1a37969.1709886922.git.u.kleine-koenig@pengutronix.de>

Introduce x86_64 and arm64 functions to get the hypervisor version
information and store it in a structure for simpler parsing.

Use the new function to get and parse the version at boot time. While at
it, move the printing code to hv_common_init() so it is not duplicated.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/1709852618-29110-1-git-send-email-nunodasneves@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1709852618-29110-1-git-send-email-nunodasneves@linux.microsoft.com>

Currently, the secondary CPUs in Hyper-V VTL context lack support for
parallel startup. Therefore, relying on the single initial_stack fetched
from the current task structure suffices for all vCPUs.

However, common initial_stack risks stack corruption when parallel startup
is enabled. In order to facilitate parallel startup, use the initial_stack
from the per CPU idle thread instead of the current task.

Fixes: 3be1bc2fe9d2 ("x86/hyperv: VTL support for Hyper-V")
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/1709452896-13342-1-git-send-email-ssengar@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1709452896-13342-1-git-send-email-ssengar@linux.microsoft.com>

The HV_REGISTER_ are used as arguments to hv_set/get_register(), which
delegate to arch-specific mechanisms for getting/setting synthetic
Hyper-V MSRs.

On arm64, HV_REGISTER_ defines are synthetic VP registers accessed via
the get/set vp registers hypercalls. The naming matches the TLFS
document, although these register names are not specific to arm64.

However, on x86 the prefix HV_REGISTER_ indicates Hyper-V MSRs accessed
via rdmsrl()/wrmsrl(). This is not consistent with the TLFS doc, where
HV_REGISTER_ is *only* used for used for VP register names used by
the get/set register hypercalls.

To fix this inconsistency and prevent future confusion, change the
arch-generic aliases used by callers of hv_set/get_register() to have
the prefix HV_MSR_ instead of HV_REGISTER_.

Use the prefix HV_X64_MSR_ for the x86-only Hyper-V MSRs. On x86, the
generic HV_MSR_'s point to the corresponding HV_X64_MSR_.

Move the arm64 HV_REGISTER_* defines to the asm-generic hyperv-tlfs.h,
since these are not specific to arm64. On arm64, the generic HV_MSR_'s
point to the corresponding HV_REGISTER_.

While at it, rename hv_get/set_registers() and related functions to
hv_get/set_msr(), hv_get/set_nested_msr(), etc. These are only used for
Hyper-V MSRs and this naming makes that clear.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/1708440933-27125-1-git-send-email-nunodasneves@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1708440933-27125-1-git-send-email-nunodasneves@linux.microsoft.com>

Now that the driver core can properly handle constant struct bus_type,
move the hv_bus variable to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240204-bus_cleanup-hv-v1-1-521bd4140673@marliere.net
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240204-bus_cleanup-hv-v1-1-521bd4140673@marliere.net>

A previous commit left the indentation in create_gpadl_header()
unchanged for ease of review. Update the indentation and remove
line wrap in two places where it is no longer necessary.

No functional change.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240111165451.269418-2-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240111165451.269418-2-mhklinux@outlook.com>

create_gpadl_header() creates a message header, and one or more message
bodies if the number of GPADL entries exceeds what fits in the
header. Currently the code for creating the message header is
duplicated in the two halves of the main "if" statement governing
whether message bodies are created.

Eliminate the duplication by making minor tweaks to the logic and
associated comments. While here, simplify the handling of memory
allocation errors, and use umin() instead of open coding it.

For ease of review, the indentation of sizable chunks of code is
*not* changed.  A follow-on patch updates only the indentation.

No functional change.

Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240111165451.269418-1-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240111165451.269418-1-mhklinux@outlook.com>

Hyper-V hosts can omit the _SYNC flag to due a bug on resume from modern
suspend. In such a case, the guest may fail to update its time-of-day to
account for the period when it was suspended, and could proceed with a
significantly wrong time-of-day. In such a case when the guest is
significantly behind, fix it by treating a _SAMPLE the same as if _SYNC
was received so that the guest time-of-day is updated.

This is hidden behind param hv_utils.timesync_implicit.

Signed-off-by: Peter Martincic <pmartincic@microsoft.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20231127213524.52783-1-pmartincic@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20231127213524.52783-1-pmartincic@linux.microsoft.com>