linux-stable.git/arch/x86/include, branch linux-5.11.y

KVM: VMX: Disable preemption when probing user return MSRs

2021-05-19T08:29:56+00:00

commit 5104d7ffcf24749939bea7fdb5378d186473f890 upstream.

Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
the MSR holds a different value per logical CPU, the WRMSR could corrupt
the host's value if KVM is preempted between the RDMSR and WRMSR, and
then rescheduled on a different CPU.

Opportunistically land the helper in common x86, SVM will use the helper
in a future commit.

Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation")
Cc: stable@vger.kernel.org
Cc: Xiaoyao Li 
Signed-off-by: Sean Christopherson 
Message-Id: <20210504171734.1434054-6-seanjc@google.com>
Reviewed-by: Jim Mattson 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

x86, sched: Fix the AMD CPPC maximum performance value on certain AMD Ryzen generations

2021-05-19T08:29:49+00:00

commit 3743d55b289c203d8f77b7cd47c24926b9d186ae upstream.

Some AMD Ryzen generations has different calculation method on maximum
performance. 255 is not for all ASICs, some specific generations should use 166
as the maximum performance. Otherwise, it will report incorrect frequency value
like below:

  ~ → lscpu | grep MHz
  CPU MHz:                         3400.000
  CPU max MHz:                     7228.3198
  CPU min MHz:                     2200.0000

[ mingo: Tidied up whitespace use. ]
[ Alexander Monakov : fix 225 -> 255 typo. ]

Fixes: 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems")
Fixes: 3c55e94c0ade ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
Reported-by: Jason Bagavatsingham 
Fixed-by: Alexander Monakov 
Reviewed-by: Rafael J. Wysocki 
Signed-off-by: Huang Rui 
Signed-off-by: Ingo Molnar 
Tested-by: Jason Bagavatsingham 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210425073451.2557394-1-ray.huang@amd.com
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211791
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

KVM/VMX: Invoke NMI non-IST entry instead of IST entry

2021-05-19T08:29:26+00:00

commit a217a6593cec8b315d4c2f344bae33660b39b703 upstream.

In VMX, the host NMI handler needs to be invoked after NMI VM-Exit.
Before commit 1a5488ef0dcf6 ("KVM: VMX: Invoke NMI handler via indirect
call instead of INTn"), this was done by INTn ("int $2"). But INTn
microcode is relatively expensive, so the commit reworked NMI VM-Exit
handling to invoke the kernel handler by function call.

But this missed a detail. The NMI entry point for direct invocation is
fetched from the IDT table and called on the kernel stack.  But on 64-bit
the NMI entry installed in the IDT expects to be invoked on the IST stack.
It relies on the "NMI executing" variable on the IST stack to work
correctly, which is at a fixed position in the IST stack.  When the entry
point is unexpectedly called on the kernel stack, the RSP-addressed "NMI
executing" variable is obviously also on the kernel stack and is
"uninitialized" and can cause the NMI entry code to run in the wrong way.

Provide a non-ist entry point for VMX which shares the C-function with
the regular NMI entry and invoke the new asm entry point instead.

On 32-bit this just maps to the regular NMI entry point as 32-bit has no
ISTs and is not affected.

[ tglx: Made it independent for backporting, massaged changelog ]

Fixes: 1a5488ef0dcf6 ("KVM: VMX: Invoke NMI handler via indirect call instead of INTn")
Signed-off-by: Lai Jiangshan 
Signed-off-by: Thomas Gleixner 
Tested-by: Lai Jiangshan 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87r1imi8i1.ffs@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman

KVM: x86/mmu: Remove the defunct update_pte() paging hook

2021-05-19T08:29:26+00:00

commit c5e2184d1544f9e56140791eff1a351bea2e63b9 upstream.

Remove the update_pte() shadow paging logic, which was obsoleted by
commit 4731d4c7a077 ("KVM: MMU: out of sync shadow core"), but never
removed.  As pointed out by Yu, KVM never write protects leaf page
tables for the purposes of shadow paging, and instead marks their
associated shadow page as unsync so that the guest can write PTEs at
will.

The update_pte() path, which predates the unsync logic, optimizes COW
scenarios by refreshing leaf SPTEs when they are written, as opposed to
zapping the SPTE, restarting the guest, and installing the new SPTE on
the subsequent fault.  Since KVM no longer write-protects leaf page
tables, update_pte() is unreachable and can be dropped.

Reported-by: Yu Zhang 
Signed-off-by: Sean Christopherson 
Message-Id: <20210115004051.4099250-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

2021-04-14T06:47:08+00:00

commit fa26d0c778b432d3d9814ea82552e813b33eeb5c upstream.

Commit 8cdddd182bd7 ("ACPI: processor: Fix CPU0 wakeup in
acpi_idle_play_dead()") tried to fix CPU0 hotplug breakage by copying
wakeup_cpu0() + start_cpu0() logic from hlt_play_dead()//mwait_play_dead()
into acpi_idle_play_dead(). The problem is that these functions are not
exported to modules so when CONFIG_ACPI_PROCESSOR=m build fails.

The issue could've been fixed by exporting both wakeup_cpu0()/start_cpu0()
(the later from assembly) but it seems putting the whole pattern into a
new function and exporting it instead is better.

Reported-by: kernel test robot 
Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()")
Cc:  # 5.10+
Signed-off-by: Vitaly Kuznetsov 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()

2021-04-07T13:02:30+00:00

commit 8cdddd182bd7befae6af49c5fd612893f55d6ccb upstream.

Commit 496121c02127 ("ACPI: processor: idle: Allow probing on platforms
with one ACPI C-state") broke CPU0 hotplug on certain systems, e.g.
I'm observing the following on AWS Nitro (e.g r5b.xlarge but other
instance types are affected as well):

 # echo 0 > /sys/devices/system/cpu/cpu0/online
 # echo 1 > /sys/devices/system/cpu/cpu0/online
 <10 seconds delay>
 -bash: echo: write error: Input/output error

In fact, the above mentioned commit only revealed the problem and did
not introduce it. On x86, to wakeup CPU an NMI is being used and
hlt_play_dead()/mwait_play_dead() loops are prepared to handle it:

	/*
	 * If NMI wants to wake up CPU0, start CPU0.
	 */
	if (wakeup_cpu0())
		start_cpu0();

cpuidle_play_dead() -> acpi_idle_play_dead() (which is now being called on
systems where it wasn't called before the above mentioned commit) serves
the same purpose but it doesn't have a path for CPU0. What happens now on
wakeup is:
 - NMI is sent to CPU0
 - wakeup_cpu0_nmi() works as expected
 - we get back to while (1) loop in acpi_idle_play_dead()
 - safe_halt() puts CPU0 to sleep again.

The straightforward/minimal fix is add the special handling for CPU0 on x86
and that's what the patch is doing.

Fixes: 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state")
Signed-off-by: Vitaly Kuznetsov 
Cc: 5.10+  # 5.10+
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

Revert "xen: fix p2m size in dom0 for disabled memory hotplug case"

2021-03-30T12:30:31+00:00

commit af44a387e743ab7aa39d3fb5e29c0a973cf91bdc upstream.

This partially reverts commit 882213990d32 ("xen: fix p2m size in dom0
for disabled memory hotplug case")

There's no need to special case XEN_UNPOPULATED_ALLOC anymore in order
to correctly size the p2m. The generic memory hotplug option has
already been tied together with the Xen hotplug limit, so enabling
memory hotplug should already trigger a properly sized p2m on Xen PV.

Note that XEN_UNPOPULATED_ALLOC depends on ZONE_DEVICE which pulls in
MEMORY_HOTPLUG.

Leave the check added to __set_phys_to_machine and the adjusted
comment about EXTRA_MEM_RATIO.

Signed-off-by: Roger Pau Monné 
Reviewed-by: Boris Ostrovsky 
Link: https://lore.kernel.org/r/20210324122424.58685-3-roger.pau@citrix.com
Signed-off-by: Greg Kroah-Hartman 

[boris: fixed formatting issues]
Signed-off-by: Boris Ostrovsky

KVM: x86: Protect userspace MSR filter with SRCU, and set atomically-ish

2021-03-30T12:30:12+00:00

[ Upstream commit b318e8decf6b9ef1bcf4ca06fae6d6a2cb5d5c5c ]

Fix a plethora of issues with MSR filtering by installing the resulting
filter as an atomic bundle instead of updating the live filter one range
at a time.  The KVM_X86_SET_MSR_FILTER ioctl() isn't truly atomic, as
the hardware MSR bitmaps won't be updated until the next VM-Enter, but
the relevant software struct is atomically updated, which is what KVM
really needs.

Similar to the approach used for modifying memslots, make arch.msr_filter
a SRCU-protected pointer, do all the work configuring the new filter
outside of kvm->lock, and then acquire kvm->lock only when the new filter
has been vetted and created.  That way vCPU readers either see the old
filter or the new filter in their entirety, not some half-baked state.

Yuan Yao pointed out a use-after-free in ksm_msr_allowed() due to a
TOCTOU bug, but that's just the tip of the iceberg...

  - Nothing is __rcu annotated, making it nigh impossible to audit the
    code for correctness.
  - kvm_add_msr_filter() has an unpaired smp_wmb().  Violation of kernel
    coding style aside, the lack of a smb_rmb() anywhere casts all code
    into doubt.
  - kvm_clear_msr_filter() has a double free TOCTOU bug, as it grabs
    count before taking the lock.
  - kvm_clear_msr_filter() also has memory leak due to the same TOCTOU bug.

The entire approach of updating the live filter is also flawed.  While
installing a new filter is inherently racy if vCPUs are running, fixing
the above issues also makes it trivial to ensure certain behavior is
deterministic, e.g. KVM can provide deterministic behavior for MSRs with
identical settings in the old and new filters.  An atomic update of the
filter also prevents KVM from getting into a half-baked state, e.g. if
installing a filter fails, the existing approach would leave the filter
in a half-baked state, having already committed whatever bits of the
filter were already processed.

[*] https://lkml.kernel.org/r/20210312083157.25403-1-yaoyuan0329os@gmail.com

Fixes: 1a155254ff93 ("KVM: x86: Introduce MSR filtering")
Cc: stable@vger.kernel.org
Cc: Alexander Graf 
Reported-by: Yuan Yao 
Signed-off-by: Sean Christopherson 
Message-Id: <20210316184436.2544875-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini 
Signed-off-by: Sasha Levin

static_call: Allow module use without exposing static_call_key

2021-03-30T12:30:12+00:00

[ Upstream commit 73f44fe19d359635a607e8e8daa0da4001c1cfc2 ]

When exporting static_call_key; with EXPORT_STATIC_CALL*(), the module
can use static_call_update() to change the function called.  This is
not desirable in general.

Not exporting static_call_key however also disallows usage of
static_call(), since objtool needs the key to construct the
static_call_site.

Solve this by allowing objtool to create the static_call_site using
the trampoline address when it builds a module and cannot find the
static_call_key symbol. The module loader will then try and map the
trampole back to a key before it constructs the normal sites list.

Doing this requires a trampoline -> key associsation, so add another
magic section that keeps those.

Originally-by: Peter Zijlstra (Intel) 
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Link: https://lkml.kernel.org/r/20210127231837.ifddpn7rhwdaepiu@treble
Signed-off-by: Sasha Levin

x86: Introduce TS_COMPAT_RESTART to fix get_nr_restart_syscall()

2021-03-24T10:54:16+00:00

commit 8c150ba2fb5995c84a7a43848250d444a3329a7d upstream.

The comment in get_nr_restart_syscall() says:

	 * The problem is that we can get here when ptrace pokes
	 * syscall-like values into regs even if we're not in a syscall
	 * at all.

Yes, but if not in a syscall then the

	status & (TS_COMPAT|TS_I386_REGS_POKED)

check below can't really help:

	- TS_COMPAT can't be set

	- TS_I386_REGS_POKED is only set if regs->orig_ax was changed by
	  32bit debugger; and even in this case get_nr_restart_syscall()
	  is only correct if the tracee is 32bit too.

Suppose that a 64bit debugger plays with a 32bit tracee and

	* Tracee calls sleep(2)	// TS_COMPAT is set
	* User interrupts the tracee by CTRL-C after 1 sec and does
	  "(gdb) call func()"
	* gdb saves the regs by PTRACE_GETREGS
	* does PTRACE_SETREGS to set %rip='func' and %orig_rax=-1
	* PTRACE_CONT		// TS_COMPAT is cleared
	* func() hits int3.
	* Debugger catches SIGTRAP.
	* Restore original regs by PTRACE_SETREGS.
	* PTRACE_CONT

get_nr_restart_syscall() wrongly returns __NR_restart_syscall==219, the
tracee calls ia32_sys_call_table[219] == sys_madvise.

Add the sticky TS_COMPAT_RESTART flag which survives after return to user
mode. It's going to be removed in the next step again by storing the
information in the restart block. As a further cleanup it might be possible
to remove also TS_I386_REGS_POKED with that.

Test-case:

  $ cvs -d :pserver:anoncvs:anoncvs@sourceware.org:/cvs/systemtap co ptrace-tests
  $ gcc -o erestartsys-trap-debuggee ptrace-tests/tests/erestartsys-trap-debuggee.c --m32
  $ gcc -o erestartsys-trap-debugger ptrace-tests/tests/erestartsys-trap-debugger.c -lutil
  $ ./erestartsys-trap-debugger
  Unexpected: retval 1, errno 22
  erestartsys-trap-debugger: ptrace-tests/tests/erestartsys-trap-debugger.c:421

Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code")
Reported-by: Jan Kratochvil 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210201174709.GA17895@redhat.com
Signed-off-by: Greg Kroah-Hartman