lkml.org 
[lkml]   [2019]   [Nov]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: x86/iopl] x86/tss: Fix and move VMX BUILD_BUG_ON()
The following commit has been merged into the x86/iopl branch of tip:

Commit-ID: 4dee588dc12914966faf902932238cb09a493d1c
Gitweb: https://git.kernel.org/tip/4dee588dc12914966faf902932238cb09a493d1c
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 13 Nov 2019 21:42:44 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:00 +01:00

x86/tss: Fix and move VMX BUILD_BUG_ON()

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>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.097140143@linutronix.de


---
arch/x86/kvm/vmx/vmx.c | 8 --------
arch/x86/mm/cpu_entry_area.c | 8 ++++++++
2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5d21a4a..311fd48 100644
--- 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 *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 */

diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 752ad11..2c1d422 100644
--- 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(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);

\
 
 \ /
  Last update: 2019-11-15 22:13    [W:0.911 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site