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    Subject[PATCH] KVM: VMX: fix tlb flush with invalid root
    Commit 341d9b535b6c simplify reload logic while entry guest mode, it
    can avoid unnecessary sync-root if KVM_REQ_MMU_RELOAD and
    KVM_REQ_MMU_SYNC both set.

    But, it cause a issue that when we handle 'KVM_REQ_TLB_FLUSH', the
    root is invalid, it is triggered during my test:

    Kernel BUG at ffffffffa00212b8 [verbose debug info unavailable]
    ......

    [<ffffffff810f5caf>] ? fget_light+0x111/0x28e
    [<ffffffff81103963>] sys_ioctl+0x47/0x6a
    [<ffffffff81002c1b>] system_call_fastpath+0x16/0x1b
    Code: f0 eb 21 f7 c2 00 00 00 04 74 22 48 8d 45 f0 48 c7 45 f0 00 00 00 00 48 c7 45 f8 00 00 00 00 b9 02 00 00 00 66 0f 38 80 08 77 02 <0f> 0b c9 c3 55 48 89 e5 0f 1f 44 00 00 ba 00 68 00 00 48 8b 8f
    RIP [<ffffffffa00212b8>] vmx_flush_tlb+0xdf/0xe3 [kvm_intel]
    RSP <ffff8800be269ca8>

    Fixed by directly return if the root is not ready.

    Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
    ---
    arch/x86/include/asm/kvm_host.h | 2 ++
    arch/x86/kvm/mmu.c | 2 --
    arch/x86/kvm/vmx.c | 5 ++++-
    3 files changed, 6 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index 2bda624..8f522ec 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -40,6 +40,8 @@
    0xFFFFFF0000000000ULL)

    #define INVALID_PAGE (~(hpa_t)0)
    +#define VALID_PAGE(x) ((x) != INVALID_PAGE)
    +
    #define UNMAPPED_GVA (~(gpa_t)0)

    /* KVM Hugepage definitions for x86 */
    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index a0c5c31..399ddb0 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -92,8 +92,6 @@ module_param(oos_shadow, bool, 0644);
    #define PT_FIRST_AVAIL_BITS_SHIFT 9
    #define PT64_SECOND_AVAIL_BITS_SHIFT 52

    -#define VALID_PAGE(x) ((x) != INVALID_PAGE)
    -
    #define PT64_LEVEL_BITS 9

    #define PT64_LEVEL_SHIFT(level) \
    diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    index 806ab12..ebaaeaf 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -1831,8 +1831,11 @@ static void exit_lmode(struct kvm_vcpu *vcpu)
    static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
    {
    vpid_sync_context(to_vmx(vcpu));
    - if (enable_ept)
    + if (enable_ept) {
    + if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
    + return;
    ept_sync_context(construct_eptp(vcpu->arch.mmu.root_hpa));
    + }
    }

    static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
    --
    1.6.1.2


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