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    SubjectRe: [PATCH v5 0/8] KVM: Various fixes and improvements around kicking vCPUs
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    On 03/09/21 09:51, Vitaly Kuznetsov wrote:
    > Changes since v4 (Sean):
    > - Add Reviewed-by: tag to PATCHes 3 and 5.
    > - Drop unneeded 'vcpu' initialization from PATCH4.
    > - Return -ENOMEM from kvm_init() when cpumask allocation fails and drop
    > unnecessary braces (PATCH 7).
    > - Drop cpumask_available() check from kvm_kick_many_cpus() and convert
    > kvm_make_vcpu_request()'s parameter from 'cpumask_var_t' to
    > 'struct cpumask *' (PATCH 8)
    >
    > This series is a continuation to Sean's "[PATCH 0/2] VM: Fix a benign race
    > in kicking vCPUs" work and v2 for my "KVM: Optimize
    > kvm_make_vcpus_request_mask() a bit"/"KVM: x86: Fix stack-out-of-bounds
    > memory access from ioapic_write_indirect()" patchset.

    Now queued 3-4-5-7-8 as well, thanks.

    Paolo

    > From Sean:
    >
    > "Fix benign races when kicking vCPUs where the task doing the kicking can
    > consume a stale vcpu->cpu. The races are benign because of the
    > impliciations of task migration with respect to interrupts and being in
    > guest mode, but IMO they're worth fixing if only as an excuse to
    > document the flows.
    >
    > Patch 2 is a tangentially related cleanup to prevent future me from
    > trying to get rid of the NULL check on the cpumask parameters, which
    > _looks_ like it can't ever be NULL, but has a subtle edge case due to the
    > way CONFIG_CPUMASK_OFFSTACK=y handles cpumasks."
    >
    > Patch3 is a preparation to untangling kvm_make_all_cpus_request_except()
    > and kvm_make_vcpus_request_mask().
    >
    > Patch4 is a minor optimization for kvm_make_vcpus_request_mask() for big
    > guests.
    >
    > Patch5 is a minor cleanup.
    >
    > Patch6 fixes a real problem with ioapic_write_indirect() KVM does
    > out-of-bounds access to stack memory.
    >
    > Patches7 and 8 get rid of dynamic cpumask allocation for kicking vCPUs.
    >
    > Sean Christopherson (2):
    > KVM: Clean up benign vcpu->cpu data races when kicking vCPUs
    > KVM: KVM: Use cpumask_available() to check for NULL cpumask when
    > kicking vCPUs
    >
    > Vitaly Kuznetsov (6):
    > KVM: x86: hyper-v: Avoid calling kvm_make_vcpus_request_mask() with
    > vcpu_mask==NULL
    > KVM: Optimize kvm_make_vcpus_request_mask() a bit
    > KVM: Drop 'except' parameter from kvm_make_vcpus_request_mask()
    > KVM: x86: Fix stack-out-of-bounds memory access from
    > ioapic_write_indirect()
    > KVM: Pre-allocate cpumasks for kvm_make_all_cpus_request_except()
    > KVM: Make kvm_make_vcpus_request_mask() use pre-allocated
    > cpu_kick_mask
    >
    > arch/x86/include/asm/kvm_host.h | 1 -
    > arch/x86/kvm/hyperv.c | 18 ++---
    > arch/x86/kvm/ioapic.c | 10 +--
    > arch/x86/kvm/x86.c | 8 +--
    > include/linux/kvm_host.h | 3 +-
    > virt/kvm/kvm_main.c | 115 +++++++++++++++++++++++---------
    > 6 files changed, 101 insertions(+), 54 deletions(-)
    >

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