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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH][RFC] Emulating real mode with x86_emulate
Howdy,Attached is a patch that begins to lay down the infrastructure for emulating real mode with x86_emulate(). With a little more refactoring, I think it could also replace the SVM emulator. The patch introduces an HVMOP hypercall to set a flag in the hvm vcpu struct to signal that real mode should be emulated with x86_emulate instead of using vm86. This is to make development a little bit easier since x86_emulate is not quite there yet wrt 16 bit emulation. It can be enabled by passing -emulate-16bit to qemu-dm (I use a wrapper script similar to qemu-dm.debug). The VT code keeps track of the whether it's in the emulator and loops on the do_resume path in x86_emulate. I think this code probably should be refactored into the common HVM code although this would require changing some of the HVM ops. This would allow SVM to use the x86_emulate to handle individual instructions. There are some issues to work out. Namely, x86_emulate appears to want blocking PIO calls which isn't conducive to the wait PIO works today in HVM. This is only a problem for instructions at the moment. I'm also a bit confused about how to properly loop in the emulator. schedule_tail is not meant to return so perhaps we should loop on emulating == 1 instead of hypercall_preempt_check? I didn't think the hypervisor was preemptable though. The current code doesn't handle non-flat segments as I don't think hvm_copy_from/to_guest handles it (which I assume it would need to). However, it is enough to start running instructions in x86_emulate so it's enough to start working on enhancing that. Regards, Anthony Liguori diff -r 3fd9b0c71b8c tools/firmware/hvmloader/hvmloader.c
--- a/tools/firmware/hvmloader/hvmloader.c Tue Mar 20 17:36:18 2007 +0000
+++ b/tools/firmware/hvmloader/hvmloader.c Sun Mar 25 13:14:43 2007 -0500
@@ -349,6 +349,14 @@ static void cmos_write_memory_size(void)
cmos_outb(0x35, (uint8_t)( alt_mem >> 8));
}
+#define DOMID_SELF (0x7FF0U)
+
+#define HVMOP_emulate_realmode 6
+struct xen_hvm_op_emulate_realmode
+{
+ uint16_t domid;
+};
+
int main(void)
{
int acpi_sz;
@@ -401,15 +409,23 @@ int main(void)
if ( !check_amd() )
{
- printf("Loading VMXAssist ...\n");
- memcpy((void *)VMXASSIST_PHYSICAL_ADDRESS,
- vmxassist, sizeof(vmxassist));
-
- printf("VMX go ...\n");
- __asm__ __volatile__(
- "jmp *%%eax"
- : : "a" (VMXASSIST_PHYSICAL_ADDRESS), "d" (0)
- );
+ printf("Loading VMXAssist ... %x\n", inl(0x595));
+ if (inl(0x595) == 0xdeadbeef) {
+ struct xen_hvm_op_emulate_realmode op;
+
+ printf("foo\n");
+ op.domid = DOMID_SELF;
+ hypercall_hvm_op(HVMOP_emulate_realmode, &op);
+ } else {
+ memcpy((void *)VMXASSIST_PHYSICAL_ADDRESS,
+ vmxassist, sizeof(vmxassist));
+
+ printf("VMX go ...\n");
+ __asm__ __volatile__(
+ "jmp *%%eax"
+ : : "a" (VMXASSIST_PHYSICAL_ADDRESS), "d" (0)
+ );
+ }
}
printf("Invoking ROMBIOS ...\n");
diff -r 3fd9b0c71b8c tools/ioemu/hw/pc.c
--- a/tools/ioemu/hw/pc.c Tue Mar 20 17:36:18 2007 +0000
+++ b/tools/ioemu/hw/pc.c Fri Mar 23 11:32:33 2007 -0500
@@ -316,6 +316,13 @@ static uint32_t ioport92_read(void *opaq
return ioport_get_a20() << 1;
}
+static uint32_t emulate_16bit_read(void *opaque, uint32_t addr)
+{
+ if (emulate_16bit)
+ return 0xdeadbeef;
+ return 0;
+}
+
/***********************************************************/
/* Bochs BIOS debug ports */
@@ -728,6 +735,8 @@ static void pc_init1(uint64_t ram_size,
bochs_bios_init();
+ register_ioport_read(0x595, 1, 4, emulate_16bit_read, NULL);
+
#ifndef CONFIG_DM
if (linux_boot) {
uint8_t bootsect[512];
diff -r 3fd9b0c71b8c tools/ioemu/vl.c
--- a/tools/ioemu/vl.c Tue Mar 20 17:36:18 2007 +0000
+++ b/tools/ioemu/vl.c Fri Mar 23 11:32:33 2007 -0500
@@ -161,6 +161,7 @@ int vnc_display = -1;
#endif
int acpi_enabled = 0;
int fd_bootchk = 1;
+int emulate_16bit;
extern int vcpus;
@@ -5535,6 +5536,7 @@ enum {
QEMU_OPTION_vncviewer,
QEMU_OPTION_vncunused,
QEMU_OPTION_vnclisten,
+ QEMU_OPTION_emulate_16bit,
};
typedef struct QEMUOption {
@@ -5614,6 +5616,7 @@ const QEMUOption qemu_options[] = {
{ "vncviewer", 0, QEMU_OPTION_vncviewer },
{ "vncunused", 0, QEMU_OPTION_vncunused },
{ "vnclisten", HAS_ARG, QEMU_OPTION_vnclisten },
+ { "emulate-16bit", 0, QEMU_OPTION_emulate_16bit },
/* temporary options */
{ "usb", 0, QEMU_OPTION_usb },
@@ -6522,6 +6525,9 @@ int main(int argc, char **argv)
case QEMU_OPTION_vnclisten:
parse_host(&vnclisten_addr, optarg);
break;
+ case QEMU_OPTION_emulate_16bit:
+ emulate_16bit = 1;
+ break;
}
}
}
diff -r 3fd9b0c71b8c tools/ioemu/vl.h
--- a/tools/ioemu/vl.h Tue Mar 20 17:36:18 2007 +0000
+++ b/tools/ioemu/vl.h Fri Mar 23 11:32:33 2007 -0500
@@ -156,6 +156,7 @@ extern void *shared_vram;
extern FILE *logfile;
+int emulate_16bit;
#if defined(__i386__) || defined(__x86_64__)
diff -r 3fd9b0c71b8c xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c Tue Mar 20 17:36:18 2007 +0000
+++ b/xen/arch/x86/hvm/hvm.c Fri Mar 23 12:16:25 2007 -0500
@@ -185,6 +185,41 @@ static int hvmop_drain_io(
out:
rcu_unlock_domain(d);
+ return rc;
+}
+
+static int hvmop_emulate_realmode(
+ XEN_GUEST_HANDLE(xen_hvm_emulate_realmode_t) uop)
+{
+ struct xen_hvm_emulate_realmode op;
+ struct domain *d;
+ struct vcpu *v;
+ int rc;
+
+ printk("hvmop_emulate_realmode\n");
+
+ if ( copy_from_guest(&op, uop, 1) )
+ return -EFAULT;
+
+ if ( op.domid != DOMID_SELF )
+ return -EPERM;
+
+ d = rcu_lock_current_domain();
+ if ( d == NULL )
+ return -ESRCH;
+
+ printk("guest requests real mode emulation\n");
+
+ for_each_vcpu(d, v)
+ {
+ v->arch.hvm_vcpu.emulate_realmode = 1;
+ }
+
+ rc = 0;
+
+ rcu_unlock_domain(d);
+ printk("foo %d\n", __LINE__);
+
return rc;
}
@@ -963,6 +998,10 @@ long do_hvm_op(unsigned long op, XEN_GUE
guest_handle_cast(arg, xen_hvm_drain_io_t));
break;
+ case HVMOP_emulate_realmode:
+ rc = hvmop_emulate_realmode(
+ guest_handle_cast(arg, xen_hvm_emulate_realmode_t));
+ break;
default:
{
diff -r 3fd9b0c71b8c xen/arch/x86/hvm/vmx/vmcs.c
--- a/xen/arch/x86/hvm/vmx/vmcs.c Tue Mar 20 17:36:18 2007 +0000
+++ b/xen/arch/x86/hvm/vmx/vmcs.c Sun Mar 25 13:02:08 2007 -0500
@@ -493,6 +493,142 @@ void vm_resume_fail(unsigned long eflags
domain_crash_synchronous();
}
+static int vmx_em_read(enum x86_segment seg,
+ unsigned long offset,
+ unsigned long *val,
+ unsigned int bytes,
+ struct x86_emulate_ctxt *ctxt)
+{
+ /* FIXME deal with non-flat segments */
+ if ( hvm_copy_from_guest_virt(val, offset, bytes) )
+ return -1;
+ return 0;
+}
+
+static int vmx_em_fetch(enum x86_segment seg,
+ unsigned long offset,
+ unsigned long *val,
+ unsigned int bytes,
+ struct x86_emulate_ctxt *ctxt)
+{
+ /* FIXME deal with non-flat segments */
+ if ( hvm_copy_from_guest_virt(val, offset, bytes) )
+ return -1;
+ return 0;
+}
+
+static int vmx_em_write(enum x86_segment seg,
+ unsigned long offset,
+ unsigned long val,
+ unsigned int bytes,
+ struct x86_emulate_ctxt *ctxt)
+{
+ /* FIXME deal with non-flat segments */
+ if ( hvm_copy_to_guest_virt(offset, &val, bytes) )
+ return -1;
+ return 0;
+}
+
+static int vmx_em_read_io(unsigned int port,
+ unsigned int bytes,
+ unsigned long *val,
+ struct x86_emulate_ctxt *ctxt)
+{
+ /* FIXME we need a smarter interface in x86_emulate since we cannot block
+ here */
+ return -1;
+}
+
+static int vmx_em_write_io(unsigned int port,
+ unsigned int bytes,
+ unsigned long val,
+ struct x86_emulate_ctxt *ctxt)
+{
+ send_pio_req(port, 1, bytes, val, IOREQ_WRITE, 0, 0);
+ return 0;
+}
+
+static int vmx_em_read_cr(unsigned int ret,
+ unsigned long *val,
+ struct x86_emulate_ctxt *ctxt)
+{
+ struct vcpu *v = current;
+
+ switch (ret) {
+ case 0:
+ *val = v->arch.hvm_vmx.cpu_shadow_cr0;
+ break;
+ case 2:
+ *val = v->arch.hvm_vmx.cpu_cr2;
+ break;
+ case 3:
+ *val = v->arch.hvm_vmx.cpu_cr3;
+ break;
+ case 4:
+ *val = v->arch.hvm_vmx.cpu_shadow_cr4;
+ break;
+ default:
+ return -1;
+ }
+ return 0;
+}
+
+static int vmx_em_write_cr(unsigned int ret,
+ unsigned long val,
+ struct x86_emulate_ctxt *ctxt)
+{
+ extern int vmx_set_cr0(unsigned long value);
+
+ if (ret != 0)
+ return -1;
+
+ return vmx_set_cr0(val);
+}
+
+static int vmx_em_write_rflags(unsigned long val,
+ struct x86_emulate_ctxt *ctxt)
+{
+ ctxt->regs->eflags = val;
+ return 0;
+}
+
+struct x86_emulate_ops em_ops = {
+ .read = vmx_em_read,
+ .write = vmx_em_write,
+ .insn_fetch = vmx_em_fetch,
+ .read_io = vmx_em_read_io,
+ .write_io = vmx_em_write_io,
+ .read_cr = vmx_em_read_cr,
+ .write_cr = vmx_em_write_cr,
+ .write_rflags = vmx_em_write_rflags,
+};
+
+static void vmx_do_emulate(struct vcpu *v)
+{
+ struct x86_emulate_ctxt ctxt;
+ struct cpu_user_regs *regs = &v->arch.guest_context.user_regs;
+
+ hvm_store_cpu_guest_regs(v, regs, NULL);
+ ctxt.regs = regs;
+
+ /* FIXME determine this dynamically */
+ ctxt.addr_size = 16;
+ ctxt.sp_size = 16;
+
+ while (!hypercall_preempt_check()) {
+ if (x86_emulate(&ctxt, &em_ops)) {
+ unsigned long eip;
+
+ eip = __vmread(GUEST_RIP);
+ printk("failed to emulate instruction at %%eip = 0x%lx\n", eip);
+ domain_crash_synchronous();
+ }
+ }
+ hvm_load_cpu_guest_regs(v, regs);
+ /* FIXME how can we ensure we loop here without taking all CPU? */
+ domain_crash_synchronous();
+}
+
void arch_vmx_do_resume(struct vcpu *v)
{
if ( v->arch.hvm_vmx.active_cpu == smp_processor_id() )
@@ -508,7 +644,11 @@ void arch_vmx_do_resume(struct vcpu *v)
}
hvm_do_resume(v);
- reset_stack_and_jump(vmx_asm_do_vmentry);
+
+ if (v->arch.hvm_vmx.emulating)
+ vmx_do_emulate(v);
+ else
+ reset_stack_and_jump(vmx_asm_do_vmentry);
}
/* Dump a section of VMCS */
diff -r 3fd9b0c71b8c xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c Tue Mar 20 17:36:18 2007 +0000
+++ b/xen/arch/x86/hvm/vmx/vmx.c Sun Mar 25 12:10:46 2007 -0500
@@ -1865,7 +1865,7 @@ static int vmx_assist(struct vcpu *v, in
return 0;
}
-static int vmx_set_cr0(unsigned long value)
+int vmx_set_cr0(unsigned long value)
{
struct vcpu *v = current;
unsigned long mfn;
@@ -1982,13 +1982,29 @@ static int vmx_set_cr0(unsigned long val
}
}
- if ( vmx_assist(v, VMX_ASSIST_INVOKE) )
+ if ( v->arch.hvm_vcpu.emulate_realmode )
+ {
+ eip = __vmread(GUEST_RIP);
+ HVM_DBG_LOG(DBG_LEVEL_1,
+ "Transfering control to x86_emulate %%eip 0x%lx\n",
eip);
+ v->arch.hvm_vmx.emulating = 1;
+ return 1;
+ }
+ else if ( vmx_assist(v, VMX_ASSIST_INVOKE) )
{
eip = __vmread(GUEST_RIP);
HVM_DBG_LOG(DBG_LEVEL_1,
"Transfering control to vmxassist %%eip 0x%lx\n", eip);
return 0; /* do not update eip! */
}
+ }
+ else if ( v->arch.hvm_vmx.emulating )
+ {
+ eip = __vmread(GUEST_RIP);
+ HVM_DBG_LOG(DBG_LEVEL_1,
+ "Enabling CR0.PE at %%eip 0x%lx\n", eip);
+ v->arch.hvm_vmx.emulating = 0;
+ return 1;
}
else if ( v->arch.hvm_vmx.vmxassist_enabled )
{
diff -r 3fd9b0c71b8c xen/include/asm-x86/hvm/vcpu.h
--- a/xen/include/asm-x86/hvm/vcpu.h Tue Mar 20 17:36:18 2007 +0000
+++ b/xen/include/asm-x86/hvm/vcpu.h Fri Mar 23 11:32:33 2007 -0500
@@ -44,6 +44,7 @@ struct hvm_vcpu {
/* Flags */
int flag_dr_dirty;
+ unsigned long emulate_realmode;
union {
struct arch_vmx_struct vmx;
diff -r 3fd9b0c71b8c xen/include/asm-x86/hvm/vmx/vmcs.h
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h Tue Mar 20 17:36:18 2007 +0000
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h Sun Mar 25 11:52:28 2007 -0500
@@ -77,6 +77,7 @@ struct arch_vmx_struct {
unsigned long cpu_cr2; /* save CR2 */
unsigned long cpu_cr3;
struct vmx_msr_state msr_state;
+ unsigned long emulating;
unsigned long vmxassist_enabled:1;
};
diff -r 3fd9b0c71b8c xen/include/public/hvm/hvm_op.h
--- a/xen/include/public/hvm/hvm_op.h Tue Mar 20 17:36:18 2007 +0000
+++ b/xen/include/public/hvm/hvm_op.h Fri Mar 23 11:32:33 2007 -0500
@@ -78,4 +78,13 @@ typedef struct xen_hvm_drain_io xen_hvm_
typedef struct xen_hvm_drain_io xen_hvm_drain_io_t;
DEFINE_XEN_GUEST_HANDLE(xen_hvm_drain_io_t);
+/* Enter into 16 bit emulation */
+#define HVMOP_emulate_realmode 6
+struct xen_hvm_emulate_realmode {
+ /* Should be DOMID_SELF */
+ domid_t domid;
+};
+typedef struct xen_hvm_emulate_realmode xen_hvm_emulate_realmode_t;
+DEFINE_XEN_GUEST_HANDLE(xen_hvm_emulate_realmode_t);
+
#endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */
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