Switch to using hvhdk.h everywhere in the kernel. This header
includes all the new Hyper-V headers in include/hyperv, which form a
superset of the definitions found in hyperv-tlfs.h.

This makes it easier to add new Hyper-V interfaces without being
restricted to those in the TLFS doc (reflected in hyperv-tlfs.h).

To be more consistent with the original Hyper-V code, the names of
some definitions are changed slightly. Update those where needed.

Update comments in mshyperv.h files to point to include/hyperv for
adding new definitions.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Easwar Hariharan <eahariha@linux.microsoft.com>
Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Easwar Hariharan <eahariha@linux.microsoft.com>
Link: https://lore.kernel.org/r/1732577084-2122-5-git-send-email-nunodasneves@linux.microsoft.com
Link: https://lore.kernel.org/r/20250108222138.1623703-3-romank@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

read_hv_sched_clock_tsc() assumes that the Hyper-V clock counter is
bigger than the variable hv_sched_clock_offset, which is cached during
early boot, but depending on the timing this assumption may be false
when a hibernated VM starts again (the clock counter starts from 0
again) and is resuming back (Note: hv_init_tsc_clocksource() is not
called during hibernation/resume); consequently,
read_hv_sched_clock_tsc() may return a negative integer (which is
interpreted as a huge positive integer since the return type is u64)
and new kernel messages are prefixed with huge timestamps before
read_hv_sched_clock_tsc() grows big enough (which typically takes
several seconds).

Fix the issue by saving the Hyper-V clock counter just before the
suspend, and using it to correct the hv_sched_clock_offset in
resume. This makes hv tsc page based sched_clock continuous and ensures
that post resume, it starts from where it left off during suspend.
Override x86_platform.save_sched_clock_state and
x86_platform.restore_sched_clock_state routines to correct this as soon
as possible.

Note: if Invariant TSC is available, the issue doesn't happen because
1) we don't register read_hv_sched_clock_tsc() for sched clock:
See commit e5313f1c5404 ("clocksource/drivers/hyper-v: Rework
clocksource and sched clock setup");
2) the common x86 code adjusts TSC similarly: see
__restore_processor_state() ->  tsc_verify_tsc_adjust(true) and
x86_platform.restore_sched_clock_state().

Cc: stable@vger.kernel.org
Fixes: 1349401ff1aa ("clocksource/drivers/hyper-v: Suspend/resume Hyper-V clocksource for hibernation")
Co-developed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240917053917.76787-1-namjain@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240917053917.76787-1-namjain@linux.microsoft.com>

Pull x86 timer updates from Thomas Gleixner:

 - Use the topology information of number of packages for making the
   decision about TSC trust instead of using the number of online nodes
   which is not reflecting the real topology.

 - Stop the PIT timer 0 when its not in use as to stop pointless
   emulation in the VMM.

 - Fix the PIT timer stop sequence for timer 0 so it truly stops both
   real hardware and buggy VMM emulations.

* tag 'x86-timers-2024-09-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tsc: Check for sockets instead of CPUs to make code match comment
  clockevents/drivers/i8253: Fix stop sequence for timer 0
  x86/i8253: Disable PIT timer 0 when not in use
  x86/tsc: Use topology_max_packages() to get package number

commit 9636be85cc5b ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when
CPUs go online/offline") introduces a new cpuhp state for hyperv
initialization.

cpuhp_setup_state() returns the state number if state is
CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN and 0 for all other states.
For the hyperv case, since a new cpuhp state was introduced it would
return 0. However, in hv_machine_shutdown(), the cpuhp_remove_state() call
is conditioned upon "hyperv_init_cpuhp > 0". This will never be true and
so hv_cpu_die() won't be called on all CPUs. This means the VP assist page
won't be reset. When the kexec kernel tries to setup the VP assist page
again, the hypervisor corrupts the memory region of the old VP assist page
causing a panic in case the kexec kernel is using that memory elsewhere.
This was originally fixed in commit dfe94d4086e4 ("x86/hyperv: Fix kexec
panic/hang issues").

Get rid of hyperv_init_cpuhp entirely since we are no longer using a
dynamic cpuhp state and use CPUHP_AP_HYPERV_ONLINE directly with
cpuhp_remove_state().

Cc: stable@vger.kernel.org
Fixes: 9636be85cc5b ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when CPUs go online/offline")
Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240828112158.3538342-1-anirudh@anirudhrb.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240828112158.3538342-1-anirudh@anirudhrb.com>

A Linux guest on Hyper-V gets the TSC frequency from a synthetic MSR, if
available. In this case, set X86_FEATURE_TSC_KNOWN_FREQ so that Linux
doesn't unnecessarily do refined TSC calibration when setting up the TSC
clocksource.

With this change, a message such as this is no longer output during boot
when the TSC is used as the clocksource:

[    1.115141] tsc: Refined TSC clocksource calibration: 2918.408 MHz

Furthermore, the guest and host will have exactly the same view of the
TSC frequency, which is important for features such as the TSC deadline
timer that are emulated by the Hyper-V host.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>
Link: https://lore.kernel.org/r/20240606025559.1631-1-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240606025559.1631-1-mhklinux@outlook.com>

According to the data sheet, writing the MODE register should stop the
counter (and thus the interrupts). This appears to work on real hardware,
at least modern Intel and AMD systems. It should also work on Hyper-V.

However, on some buggy virtual machines the mode change doesn't have any
effect until the counter is subsequently loaded (or perhaps when the IRQ
next fires).

So, set MODE 0 and then load the counter, to ensure that those buggy VMs
do the right thing and the interrupts stop. And then write MODE 0 *again*
to stop the counter on compliant implementations too.

Apparently, Hyper-V keeps firing the IRQ *repeatedly* even in mode zero
when it should only happen once, but the second MODE write stops that too.

Userspace test program (mostly written by tglx):
=====
 #include <stdio.h>
 #include <unistd.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <sys/io.h>

static __always_inline void __out##bwl(type value, uint16_t port)	\
{									\
	asm volatile("out" #bwl " %" #bw "0, %w1"			\
		     : : "a"(value), "Nd"(port));			\
}									\
									\
static __always_inline type __in##bwl(uint16_t port)			\
{									\
	type value;							\
	asm volatile("in" #bwl " %w1, %" #bw "0"			\
		     : "=a"(value) : "Nd"(port));			\
	return value;							\
}

BUILDIO(b, b, uint8_t)

 #define inb __inb
 #define outb __outb

 #define PIT_MODE	0x43
 #define PIT_CH0	0x40
 #define PIT_CH2	0x42

static int is8254;

static void dump_pit(void)
{
	if (is8254) {
		// Latch and output counter and status
		outb(0xC2, PIT_MODE);
		printf("%02x %02x %02x\n", inb(PIT_CH0), inb(PIT_CH0), inb(PIT_CH0));
	} else {
		// Latch and output counter
		outb(0x0, PIT_MODE);
		printf("%02x %02x\n", inb(PIT_CH0), inb(PIT_CH0));
	}
}

int main(int argc, char* argv[])
{
	int nr_counts = 2;

	if (argc > 1)
		nr_counts = atoi(argv[1]);

	if (argc > 2)
		is8254 = 1;

	if (ioperm(0x40, 4, 1) != 0)
		return 1;

	dump_pit();

	printf("Set oneshot\n");
	outb(0x38, PIT_MODE);
	outb(0x00, PIT_CH0);
	outb(0x0F, PIT_CH0);

	dump_pit();
	usleep(1000);
	dump_pit();

	printf("Set periodic\n");
	outb(0x34, PIT_MODE);
	outb(0x00, PIT_CH0);
	outb(0x0F, PIT_CH0);

	dump_pit();
	usleep(1000);
	dump_pit();
	dump_pit();
	usleep(100000);
	dump_pit();
	usleep(100000);
	dump_pit();

	printf("Set stop (%d counter writes)\n", nr_counts);
	outb(0x30, PIT_MODE);
	while (nr_counts--)
		outb(0xFF, PIT_CH0);

	dump_pit();
	usleep(100000);
	dump_pit();
	usleep(100000);
	dump_pit();

	printf("Set MODE 0\n");
	outb(0x30, PIT_MODE);

	dump_pit();
	usleep(100000);
	dump_pit();
	usleep(100000);
	dump_pit();

	return 0;
}
=====

Suggested-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhkelley@outlook.com>
Link: https://lore.kernel.org/all/20240802135555.564941-2-dwmw2@infradead.org

In a TDX VM without paravisor, currently the default timer is the Hyper-V
timer, which depends on the slow VM Reference Counter MSR: the Hyper-V TSC
page is not enabled in such a VM because the VM uses Invariant TSC as a
better clocksource and it's challenging to mark the Hyper-V TSC page shared
in very early boot.

Lower the rating of the Hyper-V timer so the local APIC timer becomes the
the default timer in such a VM, and print a warning in case Invariant TSC
is unavailable in such a VM. This change should cause no perceivable
performance difference.

Cc: stable@vger.kernel.org # 6.6+
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240621061614.8339-1-decui@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240621061614.8339-1-decui@microsoft.com>

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>

Rename HV_REGISTER_GUEST_OSID to HV_REGISTER_GUEST_OS_ID. This matches
the existing HV_X64_MSR_GUEST_OS_ID.

Rename HV_REGISTER_CRASH_* to HV_REGISTER_GUEST_CRASH_*. Including
GUEST_ is consistent with other #defines such as
HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE. The new names also match the TLFS
document more accurately, i.e. HvRegisterGuestCrash*.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Link: https://lore.kernel.org/r/1710285687-9160-1-git-send-email-nunodasneves@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1710285687-9160-1-git-send-email-nunodasneves@linux.microsoft.com>