Fix a bug in where kvm_make_request_and_kick() won't actually wait if the
kick races without another non-waiting kick. The issue is that all of the
conditional kvm_arch_vcpu_should_kick() implementations are missing this code:
if (req & KVM_REQUEST_WAIT)
return mode != OUTSIDE_GUEST_MODE;
Thankfully, kvm_request_needs_ipi() does the right thing, so this doesn't
affect kvm_make_all_cpus_request() or kvm_make_vcpus_request_mask(), i.e. it's
limited to x86 SNP's used of kvm_make_request_and_kick().
To fix, address this TODO:
/* TODO: merge with kvm_arch_vcpu_should_kick */
and purge kvm_arch_vcpu_should_kick(). As usual, PPC makes that difficult
because it has wonky code that is poorly documented. For reasons unknown,
kvm_vcpu_kick() unconditionally returns true on (most flavors of) PPC. To
preserve that behavior, add a compatibility wrapper in PPC, along with a
@force param to __kvm_vcpu_kick().
This series would ideally go into 7.4, even though it's obviously not small,
as guest_memfd in-place conversion massively widens the window where a missed
kick+wait can lead to the host trying to reclaim an in-use VMSA page, which
is generally fatal to the host.
Sean Christopherson (7):
KVM: s390: Drop unused and unreachable kvm_arch_vcpu_should_kick()
KVM: Add a @force param to __kvm_vcpu_kick() for PPC backwards
compatibility
KVM: PPC: Explicitly force IPIs when directly kicking vCPUs
KVM: MIPS: Rework kvm_arch_vcpu_should_kick() to use standard
implementation
KVM: Move kvm_arch_vcpu_should_kick() to common code as
kvm_vcpu_should_kick()
KVM: Plumb the full request into __kvm_vcpu_kick()
KVM: Drop kvm_vcpu_should_kick() and use kvm_request_needs_ipi()
arch/arm64/kvm/arm.c | 5 -----
arch/loongarch/kvm/vcpu.c | 5 -----
arch/mips/kvm/mips.c | 5 -----
arch/powerpc/include/asm/kvm_ppc.h | 13 ++++++++++++-
arch/powerpc/kvm/book3s.c | 4 ++--
arch/powerpc/kvm/book3s_pr.c | 2 +-
arch/powerpc/kvm/booke.c | 6 +++---
arch/powerpc/kvm/e500_emulate.c | 2 +-
arch/powerpc/kvm/powerpc.c | 7 +------
arch/riscv/kvm/vcpu.c | 5 -----
arch/s390/kvm/s390/s390.c | 7 -------
arch/x86/kvm/x86.c | 5 -----
include/linux/kvm_host.h | 7 +++----
virt/kvm/kvm_main.c | 28 ++++++++++++++++------------
14 files changed, 39 insertions(+), 62 deletions(-)
base-commit: 7e60162b16f9da0d2fa83da5c1723b6853a0ac1d
--
2.56.0.313.g2479322e68-goog
