85f4ff2b06
[ Upstream commit ed5e484b79e8a9b8be714bd85b6fc70bd6dc99a7 ]
In some functions the TDP iter risks not making forward progress if two
threads livelock yielding to one another. This is possible if two threads
are trying to execute wrprot_gfn_range. Each could write protect an entry
and then yield. This would reset the tdp_iter's walk over the paging
structure and the loop would end up repeating the same entry over and
over, preventing either thread from making forward progress.
Fix this issue by only yielding if the loop has made forward progress
since the last yield.
Fixes: a6a0b05da9 ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-14-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#ifndef __KVM_X86_MMU_TDP_ITER_H
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#define __KVM_X86_MMU_TDP_ITER_H
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#include <linux/kvm_host.h>
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#include "mmu.h"
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/*
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* A TDP iterator performs a pre-order walk over a TDP paging structure.
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*/
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struct tdp_iter {
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/*
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* The iterator will traverse the paging structure towards the mapping
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* for this GFN.
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*/
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gfn_t next_last_level_gfn;
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/*
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* The next_last_level_gfn at the time when the thread last
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* yielded. Only yielding when the next_last_level_gfn !=
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* yielded_gfn helps ensure forward progress.
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*/
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gfn_t yielded_gfn;
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/* Pointers to the page tables traversed to reach the current SPTE */
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u64 *pt_path[PT64_ROOT_MAX_LEVEL];
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/* A pointer to the current SPTE */
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u64 *sptep;
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/* The lowest GFN mapped by the current SPTE */
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gfn_t gfn;
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/* The level of the root page given to the iterator */
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int root_level;
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/* The lowest level the iterator should traverse to */
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int min_level;
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/* The iterator's current level within the paging structure */
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int level;
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/* A snapshot of the value at sptep */
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u64 old_spte;
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/*
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* Whether the iterator has a valid state. This will be false if the
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* iterator walks off the end of the paging structure.
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*/
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bool valid;
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};
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/*
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* Iterates over every SPTE mapping the GFN range [start, end) in a
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* preorder traversal.
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*/
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#define for_each_tdp_pte_min_level(iter, root, root_level, min_level, start, end) \
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for (tdp_iter_start(&iter, root, root_level, min_level, start); \
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iter.valid && iter.gfn < end; \
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tdp_iter_next(&iter))
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#define for_each_tdp_pte(iter, root, root_level, start, end) \
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for_each_tdp_pte_min_level(iter, root, root_level, PG_LEVEL_4K, start, end)
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u64 *spte_to_child_pt(u64 pte, int level);
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void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
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int min_level, gfn_t next_last_level_gfn);
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void tdp_iter_next(struct tdp_iter *iter);
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u64 *tdp_iter_root_pt(struct tdp_iter *iter);
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#endif /* __KVM_X86_MMU_TDP_ITER_H */
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