Messages in this thread | | | Subject | Re: [patch V2 04/16] x86/tss: Fix and move VMX BUILD_BUG_ON() | From | Paolo Bonzini <> | Date | Mon, 11 Nov 2019 23:44:19 +0100 |
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On 11/11/19 23:03, Thomas Gleixner wrote: > The BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 == 0x67) in the VMX code is bogus in > two aspects: > > 1) This wants to be in generic x86 code simply to catch issues even when > VMX is disabled in Kconfig. > > 2) The IO_BITMAP_OFFSET is not the right thing to check because it makes > asssumptions about the layout of tss_struct. Nothing requires that the > I/O bitmap is placed right after x86_tss, which is the hardware mandated > tss structure. It pointlessly makes restrictions on the struct > tss_struct layout. > > The proper thing to check is: > > - Offset of x86_tss in tss_struct is 0 > - Size of x86_tss == 0x68 > > Move it to the other build time TSS checks and make it do the right thing. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Cc: Paolo Bonzini <pbonzini@redhat.com> > --- > V2: New patch > --- > arch/x86/kvm/vmx/vmx.c | 8 -------- > arch/x86/mm/cpu_entry_area.c | 8 ++++++++ > 2 files changed, 8 insertions(+), 8 deletions(-) > > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -1338,14 +1338,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu > (unsigned long)&get_cpu_entry_area(cpu)->tss.x86_tss); > vmcs_writel(HOST_GDTR_BASE, (unsigned long)gdt); /* 22.2.4 */ > > - /* > - * VM exits change the host TR limit to 0x67 after a VM > - * exit. This is okay, since 0x67 covers everything except > - * the IO bitmap and have have code to handle the IO bitmap > - * being lost after a VM exit. > - */ > - BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 != 0x67); > - > rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp); > vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */ > > --- a/arch/x86/mm/cpu_entry_area.c > +++ b/arch/x86/mm/cpu_entry_area.c > @@ -161,6 +161,14 @@ static void __init setup_cpu_entry_area( > BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^ > offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK); > BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0); > + /* > + * VMX changes the host TR limit to 0x67 after a VM exit. This is > + * okay, since 0x67 covers the size of struct x86_hw_tss. Make sure > + * that this is correct. > + */ > + BUILD_BUG_ON(offsetof(struct tss_struct, x86_tss) != 0); > + BUILD_BUG_ON(sizeof(struct x86_hw_tss) != 0x68); > + > cea_map_percpu_pages(&cea->tss, &per_cpu(cpu_tss_rw, cpu), > sizeof(struct tss_struct) / PAGE_SIZE, tss_prot); > > >
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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