Commit b19ee2ff authored by Nadav Amit's avatar Nadav Amit Committed by Radim Krčmář

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: default avatarNadav Amit <nadav.amit@gmail.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent 13e98fd1
......@@ -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
......
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