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| author | Nadav Amit <nadav.amit@gmail.com> | 2016-05-11 08:04:29 -0700 |
|---|---|---|
| committer | Radim Krčmář <rkrcmar@redhat.com> | 2016-06-02 17:38:50 +0200 |
| commit | b19ee2ff3b287fea48a2896a381e31319394fe58 (patch) | |
| tree | f1678e5632fa80ba384d77546a26fd2b6a963725 | |
| parent | 13e98fd1efc7f65cab1bba6cfab7859840f9aa66 (diff) | |
| download | linux-b19ee2ff3b287fea48a2896a381e31319394fe58.tar.gz linux-b19ee2ff3b287fea48a2896a381e31319394fe58.tar.bz2 linux-b19ee2ff3b287fea48a2896a381e31319394fe58.zip | |
KVM: x86: avoid write-tearing of TDP
In theory, nothing prevents the compiler from write-tearing PTEs, or
split PTE writes. These partially-modified PTEs can be fetched by other
cores and cause mayhem. I have not really encountered such case in
real-life, but it does seem possible.
For example, the compiler may try to do something creative for
kvm_set_pte_rmapp() and perform multiple writes to the PTE.
Signed-off-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
| -rw-r--r-- | arch/x86/kvm/mmu.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 24e800116ab4..def97b3a392b 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -336,12 +336,12 @@ static gfn_t pse36_gfn_delta(u32 gpte) #ifdef CONFIG_X86_64 static void __set_spte(u64 *sptep, u64 spte) { - *sptep = spte; + WRITE_ONCE(*sptep, spte); } static void __update_clear_spte_fast(u64 *sptep, u64 spte) { - *sptep = spte; + WRITE_ONCE(*sptep, spte); } static u64 __update_clear_spte_slow(u64 *sptep, u64 spte) @@ -390,7 +390,7 @@ static void __set_spte(u64 *sptep, u64 spte) */ smp_wmb(); - ssptep->spte_low = sspte.spte_low; + WRITE_ONCE(ssptep->spte_low, sspte.spte_low); } static void __update_clear_spte_fast(u64 *sptep, u64 spte) @@ -400,7 +400,7 @@ static void __update_clear_spte_fast(u64 *sptep, u64 spte) ssptep = (union split_spte *)sptep; sspte = (union split_spte)spte; - ssptep->spte_low = sspte.spte_low; + WRITE_ONCE(ssptep->spte_low, sspte.spte_low); /* * If we map the spte from present to nonpresent, we should clear |