Searched hist:"6 f390916c4fb359507d9ac4bf1b28a4f8abee5c0" (Results 1 – 2 of 2) sorted by relevance
| /openbmc/linux/arch/s390/kvm/ |
| H A D | kvm-s390.c | diff 6f390916c4fb359507d9ac4bf1b28a4f8abee5c0 Fri Oct 08 21:11:56 CDT 2021 Sean Christopherson <seanjc@google.com> KVM: s390: Ensure kvm_arch_no_poll() is read once when blocking vCPU
Wrap s390's halt_poll_max_steal with READ_ONCE and snapshot the result of
kvm_arch_no_poll() in kvm_vcpu_block() to avoid a mostly-theoretical,
largely benign bug on s390 where the result of kvm_arch_no_poll() could
change due to userspace modifying halt_poll_max_steal while the vCPU is
blocking. The bug is largely benign as it will either cause KVM to skip
updating halt-polling times (no_poll toggles false=>true) or to update
halt-polling times with a slightly flawed block_ns.
Note, READ_ONCE is unnecessary in the current code, add it in case the
arch hook is ever inlined, and to provide a hint that userspace can
change the param at will.
Fixes: 8b905d28ee17 ("KVM: s390: provide kvm_arch_no_poll function")
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
| /openbmc/linux/virt/kvm/ |
| H A D | kvm_main.c | diff 6f390916c4fb359507d9ac4bf1b28a4f8abee5c0 Fri Oct 08 21:11:56 CDT 2021 Sean Christopherson <seanjc@google.com> KVM: s390: Ensure kvm_arch_no_poll() is read once when blocking vCPU
Wrap s390's halt_poll_max_steal with READ_ONCE and snapshot the result of
kvm_arch_no_poll() in kvm_vcpu_block() to avoid a mostly-theoretical,
largely benign bug on s390 where the result of kvm_arch_no_poll() could
change due to userspace modifying halt_poll_max_steal while the vCPU is
blocking. The bug is largely benign as it will either cause KVM to skip
updating halt-polling times (no_poll toggles false=>true) or to update
halt-polling times with a slightly flawed block_ns.
Note, READ_ONCE is unnecessary in the current code, add it in case the
arch hook is ever inlined, and to provide a hint that userspace can
change the param at will.
Fixes: 8b905d28ee17 ("KVM: s390: provide kvm_arch_no_poll function")
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|