On 2017/12/07 02:19, Jim Mattson wrote:
On Wed, Dec 6, 2017 at 3:17 AM, Quan Xu <quan.xu0@xxxxxxxxx> wrote:
On 2017/12/06 05:26, Radim Krčmář wrote:
2017-12-01 10:21-0800, Jim Mattson:
Since we no longer allow any I/O ports to be passed through to the guest,
we can use the same page for I/O bitmap A and I/O bitmap B.
I think we can disable the feature and save the second page as well:
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e25c55ea2eb7..80859a7cdf6d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3624,7 +3624,7 @@ static __init int setup_vmcs_config(struct
vmcs_config *vmcs_conf)
#endif
CPU_BASED_CR3_LOAD_EXITING |
CPU_BASED_CR3_STORE_EXITING |
- CPU_BASED_USE_IO_BITMAPS |
+ CPU_BASED_UNCOND_IO_EXITING |
CPU_BASED_MOV_DR_EXITING |
CPU_BASED_USE_TSC_OFFSETING |
CPU_BASED_INVLPG_EXITING |
Jim / Radim,
As a logical processor uses these bitmaps if and only if the “use I/O
bitmaps” control is 1.
Since we drop 'CPU_BASED_USE_IOBITMAPS' in vmcs configuration.. We could
also drop
'IO_BITMAP_A'/'IO_BITMAP_B'/'vmx_io_bitmap_a'/'vmx_io_bitmap_b' for a
furthermore
cleanup as below:
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 04b4dbc..3e4f760 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -771,8 +771,6 @@ static struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu
*vcpu)
FIELD(HOST_FS_SELECTOR, host_fs_selector),
FIELD(HOST_GS_SELECTOR, host_gs_selector),
FIELD(HOST_TR_SELECTOR, host_tr_selector),
- FIELD64(IO_BITMAP_A, io_bitmap_a),
- FIELD64(IO_BITMAP_B, io_bitmap_b),
Stet.
FIELD64(MSR_BITMAP, msr_bitmap),
FIELD64(VM_EXIT_MSR_STORE_ADDR, vm_exit_msr_store_addr),
FIELD64(VM_EXIT_MSR_LOAD_ADDR, vm_exit_msr_load_addr),
@@ -943,8 +941,6 @@ static bool nested_vmx_is_page_fault_vmexit(struct
vmcs12 *vmcs12,
static DEFINE_PER_CPU(spinlock_t, blocked_vcpu_on_cpu_lock);
enum {
- VMX_IO_BITMAP_A,
- VMX_IO_BITMAP_B,
VMX_MSR_BITMAP_LEGACY,
VMX_MSR_BITMAP_LONGMODE,
VMX_MSR_BITMAP_LEGACY_X2APIC_APICV,
@@ -958,8 +954,6 @@ 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_msr_bitmap_legacy (vmx_bitmap[VMX_MSR_BITMAP_LEGACY])
#define vmx_msr_bitmap_longmode (vmx_bitmap[VMX_MSR_BITMAP_LONGMODE])
#define vmx_msr_bitmap_legacy_x2apic_apicv
(vmx_bitmap[VMX_MSR_BITMAP_LEGACY_X2APIC_APICV])
@@ -3632,7 +3626,7 @@ static __init int setup_vmcs_config(struct vmcs_config
*vmcs_conf)
#endif
CPU_BASED_CR3_LOAD_EXITING |
CPU_BASED_CR3_STORE_EXITING |
- CPU_BASED_USE_IO_BITMAPS |
+ CPU_BASED_UNCOND_IO_EXITING |
Is it safe to assume that all CPUs (both physical and virtual)
currently running kvm will support this control bit?
Jim, I don't see some conditions to "Use I/O bitmaps" or "Unconditional
I/O exiting" in Intel SDM.
and in prepare_vmcs02(),
...
/*
* 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;
...
So I think it is safe for cpu and vcpu.
as sdm said, """ "Unconditional I/O exiting" -- This control determines
whether executions of I/O
instructions (IN, INS/INSB/INSW/INSD, OUT, and OUTS/OUTSB/OUTSW/OUTSD)
cause VM exits.
"Use I/O bitmaps" -- For this control, “0” means “do not use I/O
bitmaps” and “1” means
“use I/O bitmaps.” """"
I think it is safe for all CPU, if we clear the "Use I/O bitmaps". It
doesn't matter whether
the "Unconditional I/O exiting" is set or clear.. Of Course both bits
are clear, which may
make host/guest to the incorrect field.
is it? Radim, could you help me double check it?
Quan
Alibaba Cloud
CPU_BASED_MOV_DR_EXITING |
CPU_BASED_USE_TSC_OFFSETING |
CPU_BASED_INVLPG_EXITING |
@@ -5445,10 +5439,6 @@ 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));
@@ -6751,13 +6741,9 @@ static __init int hardware_setup(void)
goto out;
}
- vmx_io_bitmap_b = (unsigned long *)__get_free_page(GFP_KERNEL);
memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);
- memset(vmx_io_bitmap_a, 0xff, PAGE_SIZE);
- memset(vmx_io_bitmap_b, 0xff, PAGE_SIZE);
-
memset(vmx_msr_bitmap_legacy, 0xff, PAGE_SIZE);
memset(vmx_msr_bitmap_longmode, 0xff, PAGE_SIZE);
Quan
Alibaba Cloud
