17fae1294a
An interesting thing happened when a guest Linux instance took a machine
check. The VMM unmapped the bad page from guest physical space and
passed the machine check to the guest.
Linux took all the normal actions to offline the page from the process
that was using it. But then guest Linux crashed because it said there
was a second machine check inside the kernel with this stack trace:
do_memory_failure
set_mce_nospec
set_memory_uc
_set_memory_uc
change_page_attr_set_clr
cpa_flush
clflush_cache_range_opt
This was odd, because a CLFLUSH instruction shouldn't raise a machine
check (it isn't consuming the data). Further investigation showed that
the VMM had passed in another machine check because is appeared that the
guest was accessing the bad page.
Fix is to check the scope of the poison by checking the MCi_MISC register.
If the entire page is affected, then unmap the page. If only part of the
page is affected, then mark the page as uncacheable.
This assumes that VMMs will do the logical thing and pass in the "whole
page scope" via the MCi_MISC register (since they unmapped the entire
page).
[ bp: Adjust to x86/entry changes. ]
Fixes: 284ce4011b ("x86/memory_failure: Introduce {set, clear}_mce_nospec()")
Reported-by: Jue Wang <juew@google.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jue Wang <juew@google.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200520163546.GA7977@agluck-desk2.amr.corp.intel.com
55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright 2017, Michael Ellerman, IBM Corporation.
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*/
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#ifndef _LINUX_SET_MEMORY_H_
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#define _LINUX_SET_MEMORY_H_
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#ifdef CONFIG_ARCH_HAS_SET_MEMORY
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#include <asm/set_memory.h>
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#else
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static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; }
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static inline int set_memory_rw(unsigned long addr, int numpages) { return 0; }
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static inline int set_memory_x(unsigned long addr, int numpages) { return 0; }
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static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
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#endif
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#ifndef CONFIG_ARCH_HAS_SET_DIRECT_MAP
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static inline int set_direct_map_invalid_noflush(struct page *page)
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{
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return 0;
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}
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static inline int set_direct_map_default_noflush(struct page *page)
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{
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return 0;
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}
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#endif
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#ifndef set_mce_nospec
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static inline int set_mce_nospec(unsigned long pfn, bool unmap)
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{
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return 0;
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}
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#endif
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#ifndef clear_mce_nospec
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static inline int clear_mce_nospec(unsigned long pfn)
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{
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return 0;
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}
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#endif
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#ifndef CONFIG_ARCH_HAS_MEM_ENCRYPT
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static inline int set_memory_encrypted(unsigned long addr, int numpages)
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{
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return 0;
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}
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static inline int set_memory_decrypted(unsigned long addr, int numpages)
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{
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return 0;
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}
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#endif /* CONFIG_ARCH_HAS_MEM_ENCRYPT */
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#endif /* _LINUX_SET_MEMORY_H_ */
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