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x86/tss: Fix and move VMX BUILD_BUG_ON()

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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>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
This commit is contained in:
Thomas Gleixner 2019-11-11 23:03:18 +01:00
parent 505b789996
commit 6b546e1c9a
2 changed files with 8 additions and 8 deletions
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8
arch/x86/kvm/vmx/vmx.c
View File

@ -1338,14 +1338,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu)
(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 */

8
arch/x86/mm/cpu_entry_area.c
View File

@ -161,6 +161,14 @@ static void __init setup_cpu_entry_area(unsigned int cpu)
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);