KVM: x86/mmu: Ensure forward progress when yielding in TDP MMU iter

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[ Upstream commit ed5e484b79 ]

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>

...

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Ben Gardon 2021-04-10 11:12:24 -04:00 • committed by Greg Kroah-Hartman

parent 1cd17c5c9b

commit 85f4ff2b06

3 changed files with 23 additions and 23 deletions

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18

arch/x86/kvm/mmu/tdp_iter.c

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7

arch/x86/kvm/mmu/tdp_iter.h

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21

arch/x86/kvm/mmu/tdp_mmu.c

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