From: Tim Shearer <tshearer@xxxxxxxxxxxxxxx>
This reverts commit 8eb73e2d410f00d383023fe41c0c25c6195b7389.
This reverts commit d59d51f088014f25c2562de59b9abff4f42a7468.
Reintroducing the I/O port 0x80 bypass, the removal of which incurred a significant performance penalty for NFV guests due to excessive and time-consuming VMEXITs.
Signed-off-by: Tim Shearer <tshearer@xxxxxxxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 051dab74e4e9..a2194fe02f2a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -928,6 +928,8 @@ static DEFINE_PER_CPU(struct list_head, blocked_vcpu_on_cpu);
static DEFINE_PER_CPU(spinlock_t, blocked_vcpu_on_cpu_lock);
enum {
+ VMX_IO_BITMAP_A,
+ VMX_IO_BITMAP_B,
VMX_VMREAD_BITMAP,
VMX_VMWRITE_BITMAP,
VMX_BITMAP_NR
@@ -935,6 +937,8 @@ enum {
static unsigned long *vmx_bitmap[VMX_BITMAP_NR];
+#define vmx_io_bitmap_a (vmx_bitmap[VMX_IO_BITMAP_A])
+#define vmx_io_bitmap_b (vmx_bitmap[VMX_IO_BITMAP_B])
#define vmx_vmread_bitmap (vmx_bitmap[VMX_VMREAD_BITMAP])
#define vmx_vmwrite_bitmap (vmx_bitmap[VMX_VMWRITE_BITMAP])
@@ -3701,7 +3705,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
#endif
CPU_BASED_CR3_LOAD_EXITING |
CPU_BASED_CR3_STORE_EXITING |
- CPU_BASED_UNCOND_IO_EXITING |
+ CPU_BASED_USE_IO_BITMAPS |
CPU_BASED_MOV_DR_EXITING |
CPU_BASED_USE_TSC_OFFSETING |
CPU_BASED_INVLPG_EXITING |
@@ -5657,6 +5661,10 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
#endif
int i;
+ /* I/O */
+ vmcs_write64(IO_BITMAP_A, __pa(vmx_io_bitmap_a));
+ vmcs_write64(IO_BITMAP_B, __pa(vmx_io_bitmap_b));
+
if (enable_shadow_vmcs) {
vmcs_write64(VMREAD_BITMAP, __pa(vmx_vmread_bitmap));
vmcs_write64(VMWRITE_BITMAP, __pa(vmx_vmwrite_bitmap));
@@ -6985,6 +6993,15 @@ static __init int hardware_setup(void)
memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);
+ /*
+ * Allow direct access to the PC debug port (it is often used for I/O
+ * delays, but the vmexits simply slow things down).
+ */
+ memset(vmx_io_bitmap_a, 0xff, PAGE_SIZE);
+ clear_bit(0x80, vmx_io_bitmap_a);
+
+ memset(vmx_io_bitmap_b, 0xff, PAGE_SIZE);
+
if (setup_vmcs_config(&vmcs_config) < 0) {
r = -EIO;
goto out;
@@ -10830,8 +10847,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
}
/*
- * A vmexit (to either L1 hypervisor or L0 userspace) is always needed
- * for I/O port accesses.
+ * Merging of IO bitmap not currently supported.
+ * Rather, exit every time.
*/
exec_control &= ~CPU_BASED_USE_IO_BITMAPS;
exec_control |= CPU_BASED_UNCOND_IO_EXITING;
--
2.11.0
