On Mon, Feb 18, 2013 at 10:17:14AM +0100, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
>
> This prevents trapping L2 I/O exits if L1 has neither unconditional nor
> bitmap-based exiting enabled. Furthermore, it implements I/O bitmap
> handling. We still exit unconditionally in case the CPU does not provide
> information for ins/outs.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
>
> Changes in v5:
> - still exit unconditionally if CPU refuses to provide exit
> information on ins/outs
>
> arch/x86/kvm/vmx.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 6667042..ccc7c17 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -651,6 +651,7 @@ static struct vmcs_config {
> int size;
> int order;
> u32 revision_id;
> + u32 vmx_basic_high;
> u32 pin_based_exec_ctrl;
> u32 cpu_based_exec_ctrl;
> u32 cpu_based_2nd_exec_ctrl;
> @@ -752,6 +753,11 @@ static inline bool vm_need_tpr_shadow(struct kvm *kvm)
> return (cpu_has_vmx_tpr_shadow()) && (irqchip_in_kernel(kvm));
> }
>
> +static inline bool cpu_has_stringio_exit_info(void)
> +{
> + return vmcs_config.vmx_basic_high & (VMX_BASIC_INOUT >> 32);
> +}
> +
> static inline bool cpu_has_secondary_exec_ctrls(void)
> {
> return vmcs_config.cpu_based_exec_ctrl &
> @@ -2635,6 +2641,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
> vmcs_conf->size = vmx_msr_high & 0x1fff;
> vmcs_conf->order = get_order(vmcs_config.size);
> vmcs_conf->revision_id = vmx_msr_low;
> + vmcs_conf->vmx_basic_high = vmx_msr_high;
>
> vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
> vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
> @@ -5908,6 +5915,54 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
> static const int kvm_vmx_max_exit_handlers =
> ARRAY_SIZE(kvm_vmx_exit_handlers);
>
> +static bool nested_vmx_exit_handled_io(struct kvm_vcpu *vcpu,
> + struct vmcs12 *vmcs12)
> +{
> + unsigned long exit_qualification;
> + gpa_t bitmap, last_bitmap;
> + u16 port;
> + int size;
> + u8 b;
> +
> + if (nested_cpu_has(vmcs12, CPU_BASED_UNCOND_IO_EXITING))
> + return 1;
> +
> + if (!nested_cpu_has(vmcs12, CPU_BASED_USE_IO_BITMAPS))
> + return 0;
> +
> + /* TODO: for older CPUs, derive access width from instruction */
> + if (!cpu_has_stringio_exit_info())
> + return 1;
> +
Sigh, actually I am stupid :( The information that is not available
on older cpus is address size in "VM-exit instruction information",
not operand size on exit qualification, so your v4 is correct. Except
handling of port wrap around:
If the “use I/O bitmaps” VM-execution control is 1, the instruction
causes a VM exit if it attempts to access an I/O port corresponding to a
bit set to 1 in the appropriate I/O bitmap (see Section 24.6.4). If an
I/O operation “wraps around” the 16-bit I/O-port space (accesses
ports FFFFH and 0000H), the I/O instruction causes a VM exit (the
“unconditional I/O exiting” VM-execution control is ignored if the
“use I/O bitmaps” VM-execution control is 1).
> + exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
> +
> + port = exit_qualification >> 16;
> + size = (exit_qualification & 7) + 1;
> +
> + last_bitmap = (gpa_t)-1;
> + b = -1;
> +
> + while (size > 0) {
> + if (port < 0x8000)
> + bitmap = vmcs12->io_bitmap_a;
> + else
> + bitmap = vmcs12->io_bitmap_b;
> + bitmap += (port & 0x7fff) / 8;
> +
> + if (last_bitmap != bitmap)
> + if (kvm_read_guest(vcpu->kvm, bitmap, &b, 1))
> + return 1;
> + if (b & (1 << (port & 7)))
> + return 1;
> +
> + port++;
> + size--;
> + last_bitmap = bitmap;
> + }
> +
> + return 0;
> +}
> +
> /*
> * Return 1 if we should exit from L2 to L1 to handle an MSR access access,
> * rather than handle it ourselves in L0. I.e., check whether L1 expressed
> @@ -6097,8 +6152,7 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
> case EXIT_REASON_DR_ACCESS:
> return nested_cpu_has(vmcs12, CPU_BASED_MOV_DR_EXITING);
> case EXIT_REASON_IO_INSTRUCTION:
> - /* TODO: support IO bitmaps */
> - return 1;
> + return nested_vmx_exit_handled_io(vcpu, vmcs12);
> case EXIT_REASON_MSR_READ:
> case EXIT_REASON_MSR_WRITE:
> return nested_vmx_exit_handled_msr(vcpu, vmcs12, exit_reason);
> --
> 1.7.3.4
--
Gleb.
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