linux-stable.git/arch/x86, branch linux-4.4.y Linux kernel stable tree KVM: x86: Fix misplaced backport of "work around leak of uninitialized stack contents" 2022-02-03T08:27:54+00:00 Guillaume Bertholon guillaume.bertholon@ens.fr 2022-02-01T17:17:51+00:00 52060aa13c85ef1acb53f0498bfcdf22e129ef51 The upstream commit 541ab2aeb282 ("KVM: x86: work around leak of uninitialized stack contents") resets `exception` in the function `kvm_write_guest_virt_system`. However, its backported version in stable (commit ba7f1c934f2e ("KVM: x86: work around leak of uninitialized stack contents")) applied the change in `emulator_write_std` instead. This patch moves the memset instruction back to `kvm_write_guest_virt_system`. Fixes: ba7f1c934f2e ("KVM: x86: work around leak of uninitialized stack contents") Signed-off-by: Guillaume Bertholon <guillaume.bertholon@ens.fr> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
The upstream commit 541ab2aeb282 ("KVM: x86: work around leak of
uninitialized stack contents") resets `exception` in the function
`kvm_write_guest_virt_system`.
However, its backported version in stable (commit ba7f1c934f2e
("KVM: x86: work around leak of uninitialized stack contents")) applied
the change in `emulator_write_std` instead.

This patch moves the memset instruction back to
`kvm_write_guest_virt_system`.

Fixes: ba7f1c934f2e ("KVM: x86: work around leak of uninitialized stack contents")
Signed-off-by: Guillaume Bertholon <guillaume.bertholon@ens.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
um: registers: Rename function names to avoid conflicts and build problems 2022-01-27T07:46:17+00:00 Randy Dunlap rdunlap@infradead.org 2021-09-13T06:12:52+00:00 d1c57f0f26d1d473eaed0768a3d147cee265e301 [ Upstream commit 077b7320942b64b0da182aefd83c374462a65535 ] The function names init_registers() and restore_registers() are used in several net/ethernet/ and gpu/drm/ drivers for other purposes (not calls to UML functions), so rename them. This fixes multiple build errors. Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jeff Dike <jdike@addtoit.com> Cc: Richard Weinberger <richard@nod.at> Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com> Cc: linux-um@lists.infradead.org Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 077b7320942b64b0da182aefd83c374462a65535 ]

The function names init_registers() and restore_registers() are used
in several net/ethernet/ and gpu/drm/ drivers for other purposes (not
calls to UML functions), so rename them.

This fixes multiple build errors.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: linux-um@lists.infradead.org
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
x86: Increase exception stack sizes 2021-11-26T10:58:37+00:00 Peter Zijlstra peterz@infradead.org 2021-09-15T14:19:46+00:00 17514127ee9f13fcdfe5a680172e2536550f7333 [ Upstream commit 7fae4c24a2b84a66c7be399727aca11e7a888462 ] It turns out that a single page of stack is trivial to overflow with all the tracing gunk enabled. Raise the exception stacks to 2 pages, which is still half the interrupt stacks, which are at 4 pages. Reported-by: Michael Wang <yun.wang@linux.alibaba.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/YUIO9Ye98S5Eb68w@hirez.programming.kicks-ass.net Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 7fae4c24a2b84a66c7be399727aca11e7a888462 ]

It turns out that a single page of stack is trivial to overflow with
all the tracing gunk enabled. Raise the exception stacks to 2 pages,
which is still half the interrupt stacks, which are at 4 pages.

Reported-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YUIO9Ye98S5Eb68w@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
x86/irq: Ensure PI wakeup handler is unregistered before module unload 2021-11-26T10:58:34+00:00 Sean Christopherson seanjc@google.com 2021-10-09T00:11:04+00:00 99a1f9341a43b1e25038dbb70d605107873b395c commit 6ff53f6a438f72998f56e82e76694a1df9d1ea2c upstream. Add a synchronize_rcu() after clearing the posted interrupt wakeup handler to ensure all readers, i.e. in-flight IRQ handlers, see the new handler before returning to the caller. If the caller is an exiting module and is unregistering its handler, failure to wait could result in the IRQ handler jumping into an unloaded module. The registration path doesn't require synchronization, as it's the caller's responsibility to not generate interrupts it cares about until after its handler is registered. Fixes: f6b3c72c2366 ("x86/irq: Define a global vector for VT-d Posted-Interrupts") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20211009001107.3936588-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6ff53f6a438f72998f56e82e76694a1df9d1ea2c upstream.

Add a synchronize_rcu() after clearing the posted interrupt wakeup handler
to ensure all readers, i.e. in-flight IRQ handlers, see the new handler
before returning to the caller.  If the caller is an exiting module and
is unregistering its handler, failure to wait could result in the IRQ
handler jumping into an unloaded module.

The registration path doesn't require synchronization, as it's the
caller's responsibility to not generate interrupts it cares about until
after its handler is registered.

Fixes: f6b3c72c2366 ("x86/irq: Define a global vector for VT-d Posted-Interrupts")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009001107.3936588-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
perf/x86: Reset destroy callback on event init failure 2021-10-17T08:04:44+00:00 Anand K Mistry amistry@google.com 2021-09-29T07:04:21+00:00 5ee326b8c3535ac93a3761fdf57a15ae48a80aef [ Upstream commit 02d029a41dc986e2d5a77ecca45803857b346829 ] perf_init_event tries multiple init callbacks and does not reset the event state between tries. When x86_pmu_event_init runs, it unconditionally sets the destroy callback to hw_perf_event_destroy. On the next init attempt after x86_pmu_event_init, in perf_try_init_event, if the pmu's capabilities includes PERF_PMU_CAP_NO_EXCLUDE, the destroy callback will be run. However, if the next init didn't set the destroy callback, hw_perf_event_destroy will be run (since the callback wasn't reset). Looking at other pmu init functions, the common pattern is to only set the destroy callback on a successful init. Resetting the callback on failure tries to replicate that pattern. This was discovered after commit f11dd0d80555 ("perf/x86/amd/ibs: Extend PERF_PMU_CAP_NO_EXCLUDE to IBS Op") when the second (and only second) run of the perf tool after a reboot results in 0 samples being generated. The extra run of hw_perf_event_destroy results in active_events having an extra decrement on each perf run. The second run has active_events == 0 and every subsequent run has active_events < 0. When active_events == 0, the NMI handler will early-out and not record any samples. Signed-off-by: Anand K Mistry <amistry@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210929170405.1.I078b98ee7727f9ae9d6df8262bad7e325e40faf0@changeid Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 02d029a41dc986e2d5a77ecca45803857b346829 ]

perf_init_event tries multiple init callbacks and does not reset the
event state between tries. When x86_pmu_event_init runs, it
unconditionally sets the destroy callback to hw_perf_event_destroy. On
the next init attempt after x86_pmu_event_init, in perf_try_init_event,
if the pmu's capabilities includes PERF_PMU_CAP_NO_EXCLUDE, the destroy
callback will be run. However, if the next init didn't set the destroy
callback, hw_perf_event_destroy will be run (since the callback wasn't
reset).

Looking at other pmu init functions, the common pattern is to only set
the destroy callback on a successful init. Resetting the callback on
failure tries to replicate that pattern.

This was discovered after commit f11dd0d80555 ("perf/x86/amd/ibs: Extend
PERF_PMU_CAP_NO_EXCLUDE to IBS Op") when the second (and only second)
run of the perf tool after a reboot results in 0 samples being
generated. The extra run of hw_perf_event_destroy results in
active_events having an extra decrement on each perf run. The second run
has active_events == 0 and every subsequent run has active_events < 0.
When active_events == 0, the NMI handler will early-out and not record
any samples.

Signed-off-by: Anand K Mistry <amistry@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210929170405.1.I078b98ee7727f9ae9d6df8262bad7e325e40faf0@changeid
Signed-off-by: Sasha Levin <sashal@kernel.org>
xen/x86: fix PV trap handling on secondary processors 2021-10-06T08:22:23+00:00 Jan Beulich jbeulich@suse.com 2021-09-20T16:15:11+00:00 fda79676ed9a4ca142e60f91234a5e349b3206e5 commit 0594c58161b6e0f3da8efa9c6e3d4ba52b652717 upstream. The initial observation was that in PV mode under Xen 32-bit user space didn't work anymore. Attempts of system calls ended in #GP(0x402). All of the sudden the vector 0x80 handler was not in place anymore. As it turns out up to 5.13 redundant initialization did occur: Once from cpu_initialize_context() (through its VCPUOP_initialise hypercall) and a 2nd time while each CPU was brought fully up. This 2nd initialization is now gone, uncovering that the 1st one was flawed: Unlike for the set_trap_table hypercall, a full virtual IDT needs to be specified here; the "vector" fields of the individual entries are of no interest. With many (kernel) IDT entries still(?) (i.e. at that point at least) empty, the syscall vector 0x80 ended up in slot 0x20 of the virtual IDT, thus becoming the domain's handler for vector 0x20. Make xen_convert_trap_info() fit for either purpose, leveraging the fact that on the xen_copy_trap_info() path the table starts out zero-filled. This includes moving out the writing of the sentinel, which would also have lead to a buffer overrun in the xen_copy_trap_info() case if all (kernel) IDT entries were populated. Convert the writing of the sentinel to clearing of the entire table entry rather than just the address field. (I didn't bother trying to identify the commit which uncovered the issue in 5.14; the commit named below is the one which actually introduced the bad code.) Fixes: f87e4cac4f4e ("xen: SMP guest support") Cc: stable@vger.kernel.org Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lore.kernel.org/r/7a266932-092e-b68f-f2bb-1473b61adc6e@suse.com Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 0594c58161b6e0f3da8efa9c6e3d4ba52b652717 upstream.

The initial observation was that in PV mode under Xen 32-bit user space
didn't work anymore. Attempts of system calls ended in #GP(0x402). All
of the sudden the vector 0x80 handler was not in place anymore. As it
turns out up to 5.13 redundant initialization did occur: Once from
cpu_initialize_context() (through its VCPUOP_initialise hypercall) and a
2nd time while each CPU was brought fully up. This 2nd initialization is
now gone, uncovering that the 1st one was flawed: Unlike for the
set_trap_table hypercall, a full virtual IDT needs to be specified here;
the "vector" fields of the individual entries are of no interest. With
many (kernel) IDT entries still(?) (i.e. at that point at least) empty,
the syscall vector 0x80 ended up in slot 0x20 of the virtual IDT, thus
becoming the domain's handler for vector 0x20.

Make xen_convert_trap_info() fit for either purpose, leveraging the fact
that on the xen_copy_trap_info() path the table starts out zero-filled.
This includes moving out the writing of the sentinel, which would also
have lead to a buffer overrun in the xen_copy_trap_info() case if all
(kernel) IDT entries were populated. Convert the writing of the sentinel
to clearing of the entire table entry rather than just the address
field.

(I didn't bother trying to identify the commit which uncovered the issue
in 5.14; the commit named below is the one which actually introduced the
bad code.)

Fixes: f87e4cac4f4e ("xen: SMP guest support")
Cc: stable@vger.kernel.org
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/7a266932-092e-b68f-f2bb-1473b61adc6e@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
x86/mm: Fix kern_addr_valid() to cope with existing but not present entries 2021-09-22T09:41:27+00:00 Mike Rapoport rppt@linux.ibm.com 2021-08-19T13:27:17+00:00 f1d5a6288cc13ac823439e298c29dabc7db516c2 commit 34b1999da935a33be6239226bfa6cd4f704c5c88 upstream. Jiri Olsa reported a fault when running: # cat /proc/kallsyms | grep ksys_read ffffffff8136d580 T ksys_read # objdump -d --start-address=0xffffffff8136d580 --stop-address=0xffffffff8136d590 /proc/kcore /proc/kcore: file format elf64-x86-64 Segmentation fault general protection fault, probably for non-canonical address 0xf887ffcbff000: 0000 [#1] SMP PTI CPU: 12 PID: 1079 Comm: objdump Not tainted 5.14.0-rc5qemu+ #508 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-4.fc34 04/01/2014 RIP: 0010:kern_addr_valid Call Trace: read_kcore ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? trace_hardirqs_on ? rcu_read_lock_sched_held ? lock_acquire ? lock_acquire ? rcu_read_lock_sched_held ? lock_acquire ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? lock_release ? _raw_spin_unlock ? __handle_mm_fault ? rcu_read_lock_sched_held ? lock_acquire ? rcu_read_lock_sched_held ? lock_release proc_reg_read ? vfs_read vfs_read ksys_read do_syscall_64 entry_SYSCALL_64_after_hwframe The fault happens because kern_addr_valid() dereferences existent but not present PMD in the high kernel mappings. Such PMDs are created when free_kernel_image_pages() frees regions larger than 2Mb. In this case, a part of the freed memory is mapped with PMDs and the set_memory_np_noalias() -> ... -> __change_page_attr() sequence will mark the PMD as not present rather than wipe it completely. Have kern_addr_valid() check whether higher level page table entries are present before trying to dereference them to fix this issue and to avoid similar issues in the future. Stable backporting note: ------------------------ Note that the stable marking is for all active stable branches because there could be cases where pagetable entries exist but are not valid - see 9a14aefc1d28 ("x86: cpa, fix lookup_address"), for example. So make sure to be on the safe side here and use pXY_present() accessors rather than pXY_none() which could #GP when accessing pages in the direct map. Also see: c40a56a7818c ("x86/mm/init: Remove freed kernel image areas from alias mapping") for more info. Reported-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Dave Hansen <dave.hansen@intel.com> Tested-by: Jiri Olsa <jolsa@redhat.com> Cc: <stable@vger.kernel.org> # 4.4+ Link: https://lkml.kernel.org/r/20210819132717.19358-1-rppt@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 34b1999da935a33be6239226bfa6cd4f704c5c88 upstream.

Jiri Olsa reported a fault when running:

  # cat /proc/kallsyms | grep ksys_read
  ffffffff8136d580 T ksys_read
  # objdump -d --start-address=0xffffffff8136d580 --stop-address=0xffffffff8136d590 /proc/kcore

  /proc/kcore:     file format elf64-x86-64

  Segmentation fault

  general protection fault, probably for non-canonical address 0xf887ffcbff000: 0000 [#1] SMP PTI
  CPU: 12 PID: 1079 Comm: objdump Not tainted 5.14.0-rc5qemu+ #508
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-4.fc34 04/01/2014
  RIP: 0010:kern_addr_valid
  Call Trace:
   read_kcore
   ? rcu_read_lock_sched_held
   ? rcu_read_lock_sched_held
   ? rcu_read_lock_sched_held
   ? trace_hardirqs_on
   ? rcu_read_lock_sched_held
   ? lock_acquire
   ? lock_acquire
   ? rcu_read_lock_sched_held
   ? lock_acquire
   ? rcu_read_lock_sched_held
   ? rcu_read_lock_sched_held
   ? rcu_read_lock_sched_held
   ? lock_release
   ? _raw_spin_unlock
   ? __handle_mm_fault
   ? rcu_read_lock_sched_held
   ? lock_acquire
   ? rcu_read_lock_sched_held
   ? lock_release
   proc_reg_read
   ? vfs_read
   vfs_read
   ksys_read
   do_syscall_64
   entry_SYSCALL_64_after_hwframe

The fault happens because kern_addr_valid() dereferences existent but not
present PMD in the high kernel mappings.

Such PMDs are created when free_kernel_image_pages() frees regions larger
than 2Mb. In this case, a part of the freed memory is mapped with PMDs and
the set_memory_np_noalias() -> ... -> __change_page_attr() sequence will
mark the PMD as not present rather than wipe it completely.

Have kern_addr_valid() check whether higher level page table entries are
present before trying to dereference them to fix this issue and to avoid
similar issues in the future.

Stable backporting note:
------------------------

Note that the stable marking is for all active stable branches because
there could be cases where pagetable entries exist but are not valid -
see 9a14aefc1d28 ("x86: cpa, fix lookup_address"), for example. So make
sure to be on the safe side here and use pXY_present() accessors rather
than pXY_none() which could #GP when accessing pages in the direct map.

Also see:

  c40a56a7818c ("x86/mm/init: Remove freed kernel image areas from alias mapping")

for more info.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Cc: <stable@vger.kernel.org>	# 4.4+
Link: https://lkml.kernel.org/r/20210819132717.19358-1-rppt@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
xen: fix setting of max_pfn in shared_info 2021-09-22T09:41:22+00:00 Juergen Gross jgross@suse.com 2021-07-30T09:26:21+00:00 36a260bfe7b6153b75d0869f4f56d2b679c8a565 commit 4b511d5bfa74b1926daefd1694205c7f1bcf677f upstream. Xen PV guests are specifying the highest used PFN via the max_pfn field in shared_info. This value is used by the Xen tools when saving or migrating the guest. Unfortunately this field is misnamed, as in reality it is specifying the number of pages (including any memory holes) of the guest, so it is the highest used PFN + 1. Renaming isn't possible, as this is a public Xen hypervisor interface which needs to be kept stable. The kernel will set the value correctly initially at boot time, but when adding more pages (e.g. due to memory hotplug or ballooning) a real PFN number is stored in max_pfn. This is done when expanding the p2m array, and the PFN stored there is even possibly wrong, as it should be the last possible PFN of the just added P2M frame, and not one which led to the P2M expansion. Fix that by setting shared_info->max_pfn to the last possible PFN + 1. Fixes: 98dd166ea3a3c3 ("x86/xen/p2m: hint at the last populated P2M entry") Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Link: https://lore.kernel.org/r/20210730092622.9973-2-jgross@suse.com Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 4b511d5bfa74b1926daefd1694205c7f1bcf677f upstream.

Xen PV guests are specifying the highest used PFN via the max_pfn
field in shared_info. This value is used by the Xen tools when saving
or migrating the guest.

Unfortunately this field is misnamed, as in reality it is specifying
the number of pages (including any memory holes) of the guest, so it
is the highest used PFN + 1. Renaming isn't possible, as this is a
public Xen hypervisor interface which needs to be kept stable.

The kernel will set the value correctly initially at boot time, but
when adding more pages (e.g. due to memory hotplug or ballooning) a
real PFN number is stored in max_pfn. This is done when expanding the
p2m array, and the PFN stored there is even possibly wrong, as it
should be the last possible PFN of the just added P2M frame, and not
one which led to the P2M expansion.

Fix that by setting shared_info->max_pfn to the last possible PFN + 1.

Fixes: 98dd166ea3a3c3 ("x86/xen/p2m: hint at the last populated P2M entry")
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20210730092622.9973-2-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
KVM: x86: Update vCPU's hv_clock before back to guest when tsc_offset is adjusted 2021-09-22T09:41:22+00:00 Zelin Deng zelin.deng@linux.alibaba.com 2021-04-28T02:22:01+00:00 8eccf9266c173d398dbe4dbfe469d542fe498a2b commit d9130a2dfdd4b21736c91b818f87dbc0ccd1e757 upstream. When MSR_IA32_TSC_ADJUST is written by guest due to TSC ADJUST feature especially there's a big tsc warp (like a new vCPU is hot-added into VM which has been up for a long time), tsc_offset is added by a large value then go back to guest. This causes system time jump as tsc_timestamp is not adjusted in the meantime and pvclock monotonic character. To fix this, just notify kvm to update vCPU's guest time before back to guest. Cc: stable@vger.kernel.org Signed-off-by: Zelin Deng <zelin.deng@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1619576521-81399-2-git-send-email-zelin.deng@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit d9130a2dfdd4b21736c91b818f87dbc0ccd1e757 upstream.

When MSR_IA32_TSC_ADJUST is written by guest due to TSC ADJUST feature
especially there's a big tsc warp (like a new vCPU is hot-added into VM
which has been up for a long time), tsc_offset is added by a large value
then go back to guest. This causes system time jump as tsc_timestamp is
not adjusted in the meantime and pvclock monotonic character.
To fix this, just notify kvm to update vCPU's guest time before back to
guest.

Cc: stable@vger.kernel.org
Signed-off-by: Zelin Deng <zelin.deng@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1619576521-81399-2-git-send-email-zelin.deng@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
x86/reboot: Limit Dell Optiplex 990 quirk to early BIOS versions 2021-09-22T09:41:18+00:00 Paul Gortmaker paul.gortmaker@windriver.com 2021-05-30T16:24:47+00:00 c0c3b0b810777726c0ce88c94f845be0b4ff6683 commit a729691b541f6e63043beae72e635635abe5dc09 upstream. When this platform was relatively new in November 2011, with early BIOS revisions, a reboot quirk was added in commit 6be30bb7d750 ("x86/reboot: Blacklist Dell OptiPlex 990 known to require PCI reboot") However, this quirk (and several others) are open-ended to all BIOS versions and left no automatic expiry if/when the system BIOS fixed the issue, meaning that nobody is likely to come along and re-test. What is really problematic with using PCI reboot as this quirk does, is that it causes this platform to do a full power down, wait one second, and then power back on. This is less than ideal if one is using it for boot testing and/or bisecting kernels when legacy rotating hard disks are installed. It was only by chance that the quirk was noticed in dmesg - and when disabled it turned out that it wasn't required anymore (BIOS A24), and a default reboot would work fine without the "harshness" of power cycling the machine (and disks) down and up like the PCI reboot does. Doing a bit more research, it seems that the "newest" BIOS for which the issue was reported[1] was version A06, however Dell[2] seemed to suggest only up to and including version A05, with the A06 having a large number of fixes[3] listed. As is typical with a new platform, the initial BIOS updates come frequently and then taper off (and in this case, with a revival for CPU CVEs); a search for O990-A<ver>.exe reveals the following dates: A02 16 Mar 2011 A03 11 May 2011 A06 14 Sep 2011 A07 24 Oct 2011 A10 08 Dec 2011 A14 06 Sep 2012 A16 15 Oct 2012 A18 30 Sep 2013 A19 23 Sep 2015 A20 02 Jun 2017 A23 07 Mar 2018 A24 21 Aug 2018 While it's overkill to flash and test each of the above, it would seem likely that the issue was contained within A0x BIOS versions, given the dates above and the dates of issue reports[4] from distros. So rather than just throw out the quirk entirely, limit the scope to just those early BIOS versions, in case people are still running systems from 2011 with the original as-shipped early A0x BIOS versions. [1] https://lore.kernel.org/lkml/1320373471-3942-1-git-send-email-trenn@suse.de/ [2] https://www.dell.com/support/kbdoc/en-ca/000131908/linux-based-operating-systems-stall-upon-reboot-on-optiplex-390-790-990-systems [3] https://www.dell.com/support/home/en-ca/drivers/driversdetails?driverid=85j10 [4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/768039 Fixes: 6be30bb7d750 ("x86/reboot: Blacklist Dell OptiPlex 990 known to require PCI reboot") Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210530162447.996461-4-paul.gortmaker@windriver.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a729691b541f6e63043beae72e635635abe5dc09 upstream.

When this platform was relatively new in November 2011, with early BIOS
revisions, a reboot quirk was added in commit 6be30bb7d750 ("x86/reboot:
Blacklist Dell OptiPlex 990 known to require PCI reboot")

However, this quirk (and several others) are open-ended to all BIOS
versions and left no automatic expiry if/when the system BIOS fixed the
issue, meaning that nobody is likely to come along and re-test.

What is really problematic with using PCI reboot as this quirk does, is
that it causes this platform to do a full power down, wait one second,
and then power back on.  This is less than ideal if one is using it for
boot testing and/or bisecting kernels when legacy rotating hard disks
are installed.

It was only by chance that the quirk was noticed in dmesg - and when
disabled it turned out that it wasn't required anymore (BIOS A24), and a
default reboot would work fine without the "harshness" of power cycling the
machine (and disks) down and up like the PCI reboot does.

Doing a bit more research, it seems that the "newest" BIOS for which the
issue was reported[1] was version A06, however Dell[2] seemed to suggest
only up to and including version A05, with the A06 having a large number of
fixes[3] listed.

As is typical with a new platform, the initial BIOS updates come frequently
and then taper off (and in this case, with a revival for CPU CVEs); a
search for O990-A<ver>.exe reveals the following dates:

        A02     16 Mar 2011
        A03     11 May 2011
        A06     14 Sep 2011
        A07     24 Oct 2011
        A10     08 Dec 2011
        A14     06 Sep 2012
        A16     15 Oct 2012
        A18     30 Sep 2013
        A19     23 Sep 2015
        A20     02 Jun 2017
        A23     07 Mar 2018
        A24     21 Aug 2018

While it's overkill to flash and test each of the above, it would seem
likely that the issue was contained within A0x BIOS versions, given the
dates above and the dates of issue reports[4] from distros.  So rather than
just throw out the quirk entirely, limit the scope to just those early BIOS
versions, in case people are still running systems from 2011 with the
original as-shipped early A0x BIOS versions.

[1] https://lore.kernel.org/lkml/1320373471-3942-1-git-send-email-trenn@suse.de/
[2] https://www.dell.com/support/kbdoc/en-ca/000131908/linux-based-operating-systems-stall-upon-reboot-on-optiplex-390-790-990-systems
[3] https://www.dell.com/support/home/en-ca/drivers/driversdetails?driverid=85j10
[4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/768039

Fixes: 6be30bb7d750 ("x86/reboot: Blacklist Dell OptiPlex 990 known to require PCI reboot")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210530162447.996461-4-paul.gortmaker@windriver.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>