Re: [PATCH] KVM: x86/mmu: Remove KVM MMU write lock when accessing indirect_shadow_pages

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 6/5/23 19:17, Ben Gardon wrote:
-               if (indirect_shadow_pages)
+               if (READ_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
I don't understand the need for READ_ONCE() here. That implies that
there is something tricky going on, and I don't think that's the case.
Agree this doesn't need a READ_ONCE. Just a read is fine.
kvm_mmu_unprotect_page starts by acquiring the MMU lock, so there's
not much room to reorder anything anyway.

I agree that "there's not much room to reorder anything", but it's not a particularly formal/reassuring statement :) and READ_ONCE/WRITE_ONCE have documentation value too.

Or maybe it's because I've become used to the C11 memory model. Either way, I like the idea to use READ_ONCE/WRITE_ONCE more explicitly whenever there can be concurrent accesses (which would be data races in the C11 model), and I think Linux is moving in that direction too.

Paolo




[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux