[lkml]   [2021]   [Oct]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 3/4] KVM: X86: Use smp_rmb() to pair with smp_wmb() in mmu_try_to_unsync_pages()
On 19/10/21 13:01, Lai Jiangshan wrote:
> From: Lai Jiangshan<>
> The commit 578e1c4db2213 ("kvm: x86: Avoid taking MMU lock in
> kvm_mmu_sync_roots if no sync is needed") added smp_wmb() in
> mmu_try_to_unsync_pages(), but the corresponding smp_load_acquire()
> isn't used on the load of SPTE.W which is impossible since the load of
> SPTE.W is performed in the CPU's pagetable walking.
> This patch changes to use smp_rmb() instead. This patch fixes nothing
> but just comments since smp_rmb() is NOP and compiler barrier() is not
> required since the load of SPTE.W is before VMEXIT.

I think that even implicit loads during pagetable walking obey read-read
ordering on x86, but this is clearer and it is necessary for patch 4.


 \ /
  Last update: 2021-10-21 19:45    [W:0.078 / U:1.504 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site