linux.git/arch/x86/kernel/cpu, branch v6.6

x86/cpu: Fix AMD erratum #1485 on Zen4-based CPUs

2023-10-11T09:00:11+00:00

Fix erratum #1485 on Zen4 parts where running with STIBP disabled can
cause an #UD exception. The performance impact of the fix is negligible.

Reported-by: René Rebe 
Signed-off-by: Borislav Petkov (AMD) 
Tested-by: René Rebe 
Cc: 
Link: https://lore.kernel.org/r/D99589F4-BC5D-430B-87B2-72C20370CF57@exactcode.com

x86/resctrl: Fix kernel-doc warnings

2023-10-08T09:45:16+00:00

The kernel test robot reported kernel-doc warnings here:

  monitor.c:34: warning: Cannot understand  * @rmid_free_lru    A least recently used list of free RMIDs on line 34 - I thought it was a doc line
  monitor.c:41: warning: Cannot understand  * @rmid_limbo_count     count of currently unused but (potentially) on line 41 - I thought it was a doc line
  monitor.c:50: warning: Cannot understand  * @rmid_entry - The entry in the limbo and free lists.  on line 50 - I thought it was a doc line

We don't have a syntax for documenting individual data items via
kernel-doc, so remove the "/**" kernel-doc markers and add a hyphen
for consistency.

Fixes: 6a445edce657 ("x86/intel_rdt/cqm: Add RDT monitoring initialization")
Fixes: 24247aeeabe9 ("x86/intel_rdt/cqm: Improve limbo list processing")
Reported-by: kernel test robot 
Signed-off-by: Randy Dunlap 
Signed-off-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20231006235132.16227-1-rdunlap@infradead.org

x86/sgx: Resolves SECS reclaim vs. page fault for EAUG race

2023-09-28T23:16:40+00:00

The SGX EPC reclaimer (ksgxd) may reclaim the SECS EPC page for an
enclave and set secs.epc_page to NULL. The SECS page is used for EAUG
and ELDU in the SGX page fault handler. However, the NULL check for
secs.epc_page is only done for ELDU, not EAUG before being used.

Fix this by doing the same NULL check and reloading of the SECS page as
needed for both EAUG and ELDU.

The SECS page holds global enclave metadata. It can only be reclaimed
when there are no other enclave pages remaining. At that point,
virtually nothing can be done with the enclave until the SECS page is
paged back in.

An enclave can not run nor generate page faults without a resident SECS
page. But it is still possible for a #PF for a non-SECS page to race
with paging out the SECS page: when the last resident non-SECS page A
triggers a #PF in a non-resident page B, and then page A and the SECS
both are paged out before the #PF on B is handled.

Hitting this bug requires that race triggered with a #PF for EAUG.
Following is a trace when it happens.

BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:sgx_encl_eaug_page+0xc7/0x210
Call Trace:
 ? __kmem_cache_alloc_node+0x16a/0x440
 ? xa_load+0x6e/0xa0
 sgx_vma_fault+0x119/0x230
 __do_fault+0x36/0x140
 do_fault+0x12f/0x400
 __handle_mm_fault+0x728/0x1110
 handle_mm_fault+0x105/0x310
 do_user_addr_fault+0x1ee/0x750
 ? __this_cpu_preempt_check+0x13/0x20
 exc_page_fault+0x76/0x180
 asm_exc_page_fault+0x27/0x30

Fixes: 5a90d2c3f5ef ("x86/sgx: Support adding of pages to an initialized enclave")
Signed-off-by: Haitao Huang 
Signed-off-by: Dave Hansen 
Reviewed-by: Jarkko Sakkinen 
Reviewed-by: Kai Huang 
Acked-by: Reinette Chatre 
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20230728051024.33063-1-haitao.huang%40linux.intel.com

x86/srso: Add SRSO mitigation for Hygon processors

2023-09-28T07:57:07+00:00

Add mitigation for the speculative return stack overflow vulnerability
which exists on Hygon processors too.

Signed-off-by: Pu Wen 
Signed-off-by: Ingo Molnar 
Acked-by: Borislav Petkov (AMD) 
Cc: 
Link: https://lore.kernel.org/r/tencent_4A14812842F104E93AA722EC939483CEFF05@qq.com

x86/srso: Fix SBPB enablement for spec_rstack_overflow=off

2023-09-19T08:54:39+00:00

If the user has requested no SRSO mitigation, other mitigations can use
the lighter-weight SBPB instead of IBPB.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Ingo Molnar 
Signed-off-by: Borislav Petkov (AMD) 
Acked-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/r/b20820c3cfd1003171135ec8d762a0b957348497.1693889988.git.jpoimboe@kernel.org

x86/srso: Don't probe microcode in a guest

2023-09-19T08:54:23+00:00

To support live migration, the hypervisor sets the "lowest common
denominator" of features.  Probing the microcode isn't allowed because
any detected features might go away after a migration.

As Andy Cooper states:

  "Linux must not probe microcode when virtualised.  What it may see
  instantaneously on boot (owing to MSR_PRED_CMD being fully passed
  through) is not accurate for the lifetime of the VM."

Rely on the hypervisor to set the needed IBPB_BRTYPE and SBPB bits.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Suggested-by: Andrew Cooper 
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Ingo Molnar 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Andrew Cooper 
Acked-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/r/3938a7209606c045a3f50305d201d840e8c834c7.1693889988.git.jpoimboe@kernel.org

x86/srso: Set CPUID feature bits independently of bug or mitigation status

2023-09-19T08:54:07+00:00

Booting with mitigations=off incorrectly prevents the
X86_FEATURE_{IBPB_BRTYPE,SBPB} CPUID bits from getting set.

Also, future CPUs without X86_BUG_SRSO might still have IBPB with branch
type prediction flushing, in which case SBPB should be used instead of
IBPB.  The current code doesn't allow for that.

Also, cpu_has_ibpb_brtype_microcode() has some surprising side effects
and the setting of these feature bits really doesn't belong in the
mitigation code anyway.  Move it to earlier.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Ingo Molnar 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Nikolay Borisov 
Reviewed-by: Borislav Petkov (AMD) 
Acked-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/r/869a1709abfe13b673bdd10c2f4332ca253a40bc.1693889988.git.jpoimboe@kernel.org

x86/srso: Fix srso_show_state() side effect

2023-09-19T08:53:34+00:00

Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary
MSR write, and possibly even a (handled) exception if the microcode
hasn't been updated.

Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which
gets set by srso_select_mitigation() if the updated microcode exists.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Ingo Molnar 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Nikolay Borisov 
Acked-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@kernel.org

Merge tag 'x86-urgent-2023-09-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-09-10T17:39:31+00:00

Pull x86 fixes from Ingo Molnar:
 "Fix preemption delays in the SGX code, remove unnecessarily
  UAPI-exported code, fix a ld.lld linker (in)compatibility quirk and
  make the x86 SMP init code a bit more conservative to fix kexec()
  lockups"

* tag 'x86-urgent-2023-09-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sgx: Break up long non-preemptible delays in sgx_vepc_release()
  x86: Remove the arch_calc_vm_prot_bits() macro from the UAPI
  x86/build: Fix linker fill bytes quirk/incompatibility for ld.lld
  x86/smp: Don't send INIT to non-present and non-booted CPUs

x86/sgx: Break up long non-preemptible delays in sgx_vepc_release()

2023-09-06T21:55:09+00:00

On large enclaves we hit the softlockup warning with following call trace:

	xa_erase()
	sgx_vepc_release()
	__fput()
	task_work_run()
	do_exit()

The latency issue is similar to the one fixed in:

  8795359e35bc ("x86/sgx: Silence softlockup detection when releasing large enclaves")

The test system has 64GB of enclave memory, and all is assigned to a single VM.
Release of 'vepc' takes a longer time and causes long latencies, which triggers
the softlockup warning.

Add cond_resched() to give other tasks a chance to run and reduce
latencies, which also avoids the softlockup detector.

[ mingo: Rewrote the changelog. ]

Fixes: 540745ddbc70 ("x86/sgx: Introduce virtual EPC for use by KVM guests")
Reported-by: Yu Zhang 
Signed-off-by: Jack Wang 
Signed-off-by: Ingo Molnar 
Tested-by: Yu Zhang 
Reviewed-by: Jarkko Sakkinen 
Reviewed-by: Kai Huang 
Acked-by: Haitao Huang 
Cc: stable@vger.kernel.org