Hi,
currently we go through the emulator every time a HVM guest does an I/O
port access (in/out). This is unnecessary most of the times, as both VMX
and SVM provide all the necessary information already in the VMCS/VMCB.
String instructions are not covered by this shortcut, but they are quite
rare and we would need to access the guest memory anyway.
This patch decodes the information from VMCB/VMCS and calls a simple
handle_mmio wrapper. In handle_mmio() itself the emulation part will
simply be skipped, this approach avoids code duplication.
Since the vendor specific part is quite trivial, I implemented both the
VMX and SVM part, please check the VMX part for sanity.
I boot-tested both versions and ran some simple benchmarks.
A micro benchmark (hammering an I/O port in a tight loop) shows a
significant performance improvement (down to 66% of the time needed to
handle the intercept on an AMD K8, measured in the guest with TSC).
Even with reading a 1GB file from an emulated IDE harddisk (Dom0 cached)
I could get a 4-5% improvement.
Some guest code (e.g. the TCP stack in some Windows version) exercises
the PM-Timer I/O port (0x1F48) very often (multiple 10,000 times per
second), these workloads also benefit with up to 5% improvement from
this patch.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Regards,
Andre.
--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448-3567-12
diff -r ebd84be3420a xen/arch/x86/hvm/emulate.c
--- a/xen/arch/x86/hvm/emulate.c Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/arch/x86/hvm/emulate.c Wed Mar 31 10:17:30 2010 +0200
@@ -48,7 +48,7 @@
trace_var(event, 0/*!cycles*/, size, buffer);
}
-static int hvmemul_do_io(
+int hvmemul_do_io(
int is_mmio, paddr_t addr, unsigned long *reps, int size,
paddr_t ram_gpa, int dir, int df, void *p_data)
{
diff -r ebd84be3420a xen/arch/x86/hvm/io.c
--- a/xen/arch/x86/hvm/io.c Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/arch/x86/hvm/io.c Wed Mar 31 10:17:30 2010 +0200
@@ -171,10 +171,22 @@
struct hvm_emulate_ctxt ctxt;
struct vcpu *curr = current;
int rc;
+ unsigned long data, reps = 1;
- hvm_emulate_prepare(&ctxt, guest_cpu_user_regs());
-
- rc = hvm_emulate_one(&ctxt);
+ if ( curr->arch.hvm_vcpu.io_size == 0 ) {
+ hvm_emulate_prepare(&ctxt, guest_cpu_user_regs());
+ rc = hvm_emulate_one(&ctxt);
+ } else {
+ if ( curr->arch.hvm_vcpu.io_dir == 0 )
+ data = guest_cpu_user_regs()->eax;
+ rc = hvmemul_do_io(0, curr->arch.hvm_vcpu.io_port, &reps,
+ curr->arch.hvm_vcpu.io_size, 0,
+ curr->arch.hvm_vcpu.io_dir, 0, &data);
+ if ( curr->arch.hvm_vcpu.io_dir == 1 && rc == X86EMUL_OKAY ) {
+ memcpy(&(guest_cpu_user_regs()->eax),
+ &data, curr->arch.hvm_vcpu.io_size);
+ }
+ }
if ( curr->arch.hvm_vcpu.io_state == HVMIO_awaiting_completion )
curr->arch.hvm_vcpu.io_state = HVMIO_handle_mmio_awaiting_completion;
@@ -184,14 +196,21 @@
switch ( rc )
{
case X86EMUL_UNHANDLEABLE:
- gdprintk(XENLOG_WARNING,
- "MMIO emulation failed @ %04x:%lx: "
- "%02x %02x %02x %02x %02x %02x\n",
- hvmemul_get_seg_reg(x86_seg_cs, &ctxt)->sel,
- ctxt.insn_buf_eip,
- ctxt.insn_buf[0], ctxt.insn_buf[1],
- ctxt.insn_buf[2], ctxt.insn_buf[3],
- ctxt.insn_buf[4], ctxt.insn_buf[5]);
+ if ( curr->arch.hvm_vcpu.io_size == 0 )
+ gdprintk(XENLOG_WARNING,
+ "MMIO emulation failed @ %04x:%lx: "
+ "%02x %02x %02x %02x %02x %02x\n",
+ hvmemul_get_seg_reg(x86_seg_cs, &ctxt)->sel,
+ ctxt.insn_buf_eip,
+ ctxt.insn_buf[0], ctxt.insn_buf[1],
+ ctxt.insn_buf[2], ctxt.insn_buf[3],
+ ctxt.insn_buf[4], ctxt.insn_buf[5]);
+ else
+ gdprintk(XENLOG_WARNING,
+ "I/O emulation failed: %s 0x%04x, %i bytes, data=%08lx\n",
+ curr->arch.hvm_vcpu.io_dir ? "in" : "out",
+ curr->arch.hvm_vcpu.io_port,
+ curr->arch.hvm_vcpu.io_size, data);
return 0;
case X86EMUL_EXCEPTION:
if ( ctxt.exn_pending )
@@ -201,9 +220,15 @@
break;
}
- hvm_emulate_writeback(&ctxt);
+ if ( curr->arch.hvm_vcpu.io_size == 0 )
+ hvm_emulate_writeback(&ctxt);
+ else
+ curr->arch.hvm_vcpu.io_size = 0;
- return 1;
+ if (rc == X86EMUL_RETRY)
+ return rc;
+ else
+ return 1;
}
int handle_mmio_with_translation(unsigned long gva, unsigned long gpfn)
@@ -213,6 +238,14 @@
return handle_mmio();
}
+int handle_mmio_decoded(uint16_t port, int size, int dir)
+{
+ current->arch.hvm_vcpu.io_port = port;
+ current->arch.hvm_vcpu.io_size = size;
+ current->arch.hvm_vcpu.io_dir = dir;
+ return handle_mmio();
+}
+
void hvm_io_assist(void)
{
struct vcpu *curr = current;
diff -r ebd84be3420a xen/arch/x86/hvm/svm/emulate.c
--- a/xen/arch/x86/hvm/svm/emulate.c Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/arch/x86/hvm/svm/emulate.c Wed Mar 31 10:17:30 2010 +0200
@@ -149,6 +149,9 @@
if ( (inst_len = svm_nextrip_insn_length(v)) != 0 )
return inst_len;
+ if ( vmcb->exitcode == VMEXIT_IOIO )
+ return vmcb->exitinfo2 - vmcb->rip;
+
/* Fetch up to the next page break; we'll fetch from the next page
* later if we have to. */
fetch_addr = svm_rip2pointer(v);
diff -r ebd84be3420a xen/arch/x86/hvm/svm/svm.c
--- a/xen/arch/x86/hvm/svm/svm.c Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/arch/x86/hvm/svm/svm.c Wed Mar 31 10:17:30 2010 +0200
@@ -42,6 +42,7 @@
#include <asm/hvm/hvm.h>
#include <asm/hvm/support.h>
#include <asm/hvm/io.h>
+#include <asm/hvm/emulate.h>
#include <asm/hvm/svm/asid.h>
#include <asm/hvm/svm/svm.h>
#include <asm/hvm/svm/vmcb.h>
@@ -1244,6 +1245,23 @@
__update_guest_eip(regs, inst_len);
}
+static int svm_vmexit_do_io(struct vmcb_struct *vmcb,
+ struct cpu_user_regs *regs)
+{
+ uint16_t port;
+ int bytes, dir;
+ int rc;
+
+ port = (vmcb->exitinfo1 >> 16) & 0xFFFF;
+ bytes = ((vmcb->exitinfo1 >> 4) & 0x07);
+ dir = (vmcb->exitinfo1 & 1) ? IOREQ_READ : IOREQ_WRITE;
+
+ rc = handle_mmio_decoded(port, bytes, dir);
+ if ( rc != X86EMUL_RETRY )
+ __update_guest_eip(regs, vmcb->exitinfo2 - vmcb->rip);
+ return rc;
+}
+
static void svm_invlpg_intercept(unsigned long vaddr)
{
struct vcpu *curr = current;
@@ -1450,11 +1468,17 @@
svm_vmexit_do_hlt(vmcb, regs);
break;
+ case VMEXIT_IOIO:
+ if ( ( vmcb->exitinfo1 & ( 1 << 2 ) ) == 0 ) {
+ if ( !svm_vmexit_do_io(vmcb, regs) )
+ hvm_inject_exception(TRAP_gp_fault, 0, 0);
+ break;
+ }
+ /* fallthrough to emulation if a string instruction */
case VMEXIT_CR0_READ ... VMEXIT_CR15_READ:
case VMEXIT_CR0_WRITE ... VMEXIT_CR15_WRITE:
case VMEXIT_INVLPG:
case VMEXIT_INVLPGA:
- case VMEXIT_IOIO:
if ( !handle_mmio() )
hvm_inject_exception(TRAP_gp_fault, 0, 0);
break;
diff -r ebd84be3420a xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/arch/x86/hvm/vmx/vmx.c Wed Mar 31 10:17:30 2010 +0200
@@ -1721,6 +1721,25 @@
return 1;
}
+static int vmx_io_intercept(unsigned long exit_qualification,
+ struct cpu_user_regs *regs)
+{
+ uint16_t port;
+ int bytes, dir;
+ int rc;
+ int inst_len;
+
+ port = (exit_qualification >> 16) & 0xFFFF;
+ bytes = (exit_qualification & 0x07) + 1;
+ dir = (exit_qualification & 0x08) ? IOREQ_READ : IOREQ_WRITE;
+
+ inst_len = __get_instruction_length();
+ rc = handle_mmio_decoded(port, bytes, dir);
+ if ( rc != X86EMUL_RETRY)
+ __update_guest_eip(inst_len);
+ return rc;
+}
+
static const struct lbr_info {
u32 base, count;
} p4_lbr[] = {
@@ -2589,8 +2608,14 @@
break;
case EXIT_REASON_IO_INSTRUCTION:
- if ( !handle_mmio() )
- vmx_inject_hw_exception(TRAP_gp_fault, 0);
+ exit_qualification = __vmread(EXIT_QUALIFICATION);
+ if (exit_qualification & 0x10) {
+ if ( !handle_mmio() )
+ vmx_inject_hw_exception(TRAP_gp_fault, 0);
+ } else {
+ if ( !vmx_io_intercept(exit_qualification, regs) )
+ vmx_inject_hw_exception(TRAP_gp_fault, 0);
+ }
break;
case EXIT_REASON_INVD:
diff -r ebd84be3420a xen/include/asm-x86/hvm/emulate.h
--- a/xen/include/asm-x86/hvm/emulate.h Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/include/asm-x86/hvm/emulate.h Wed Mar 31 10:17:30 2010 +0200
@@ -46,4 +46,8 @@
enum x86_segment seg,
struct hvm_emulate_ctxt *hvmemul_ctxt);
+int hvmemul_do_io(
+ int is_mmio, paddr_t addr, unsigned long *reps, int size,
+ paddr_t ram_gpa, int dir, int df, void *p_data);
+
#endif /* __ASM_X86_HVM_EMULATE_H__ */
diff -r ebd84be3420a xen/include/asm-x86/hvm/io.h
--- a/xen/include/asm-x86/hvm/io.h Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/include/asm-x86/hvm/io.h Wed Mar 31 10:17:30 2010 +0200
@@ -100,6 +100,7 @@
void send_invalidate_req(void);
int handle_mmio(void);
int handle_mmio_with_translation(unsigned long gva, unsigned long gpfn);
+int handle_mmio_decoded(uint16_t port, int size, int dir);
void hvm_interrupt_post(struct vcpu *v, int vector, int type);
void hvm_io_assist(void);
void hvm_dpci_eoi(struct domain *d, unsigned int guest_irq,
diff -r ebd84be3420a xen/include/asm-x86/hvm/vcpu.h
--- a/xen/include/asm-x86/hvm/vcpu.h Tue Mar 30 18:31:39 2010 +0100
+++ b/xen/include/asm-x86/hvm/vcpu.h Wed Mar 31 10:17:30 2010 +0200
@@ -103,6 +103,10 @@
*/
unsigned long mmio_gva;
unsigned long mmio_gpfn;
+ uint16_t io_port;
+ int io_size;
+ unsigned io_dir;
+
/* Callback into x86_emulate when emulating FPU/MMX/XMM instructions. */
void (*fpu_exception_callback)(void *, struct cpu_user_regs *);
void *fpu_exception_callback_arg;
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