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    SubjectRe: [PATCH] KVM: vmx: fix VPID is 0000H in non-root operation
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    On 2015-09-16 13:31, Wanpeng Li wrote:
    > Reference SDM 28.1:
    >
    > The current VPID is 0000H in the following situations:
    > — Outside VMX operation. (This includes operation in system-management
    > mode under the default treatment of SMIs and SMM with VMX operation;
    > see Section 34.14.)
    > — In VMX root operation.
    > — In VMX non-root operation when the “enable VPID” VM-execution control
    > is 0.
    >
    > The VPID should never be 0000H in non-root operation when "enable VPID"
    > VM-execution control is 1. However, commit (34a1cd60: 'kvm: x86: vmx:
    > move some vmx setting from vmx_init() to hardware_setup()') remove the
    > codes which reserve 0000H for VMX root operation.
    >
    > This patch fix it by reintroducing reserve 0000H for VMX root operation.
    >
    > Reported-by: Wincy Van <fanwenyi0529@gmail.com>
    > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
    > ---
    > arch/x86/kvm/vmx.c | 2 ++
    > 1 file changed, 2 insertions(+)
    >
    > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    > index 9ff6a3f..a63b9ca 100644
    > --- a/arch/x86/kvm/vmx.c
    > +++ b/arch/x86/kvm/vmx.c
    > @@ -6056,6 +6056,8 @@ static __init int hardware_setup(void)
    > memcpy(vmx_msr_bitmap_longmode_x2apic,
    > vmx_msr_bitmap_longmode, PAGE_SIZE);
    >
    > + set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */
    > +
    > if (enable_apicv) {
    > for (msr = 0x800; msr <= 0x8ff; msr++)
    > vmx_disable_intercept_msr_read_x2apic(msr);
    >

    Good point.

    BTW, what will happen if allocate_vpid runs out of free slots and
    returns 0? Will we always fail then...?

    Jan

    --
    Siemens AG, Corporate Technology, CT RTC ITP SES-DE
    Corporate Competence Center Embedded Linux


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