# HG changeset patch
# User Keir Fraser <keir@xxxxxxxxxxxxx>
# Date 1178837344 -3600
# Node ID 60240a72e2b2676a6af652a869746dd6552eed2a
# Parent e19ddfa781c5f9c8c4e30b63baf12d3cdefc4e0e
svm: Rationalise register synchronisation to be similar to our vmx
handling.
1. Do not copy all VMCB register state in cpu_user_regs on every
vmexit.
2. Save/restore RAX inside asm stub (in particular, before STGI on
vmexit).
3. Simplify store/load_cpu_guest_regs() hook functions to synchronise
precisely the same state as VMX.
By my measurements this reduces the round-trip latency for a null
hypercall by around 150 cycles. This is about 3% of the ~5000-cycle
total on my AMD X2 system. Not a great win, but a nice extra on top of
the code rationalisation.
---
xen/arch/x86/hvm/svm/svm.c | 29 --------
xen/arch/x86/hvm/svm/x86_32/exits.S | 98 ++++++++--------------------
xen/arch/x86/hvm/svm/x86_64/exits.S | 123 ++++++++++++------------------------
3 files changed, 73 insertions(+), 177 deletions(-)
diff -r e19ddfa781c5 -r 60240a72e2b2 xen/arch/x86/hvm/svm/svm.c
--- a/xen/arch/x86/hvm/svm/svm.c Thu May 10 22:54:43 2007 +0100
+++ b/xen/arch/x86/hvm/svm/svm.c Thu May 10 23:49:04 2007 +0100
@@ -110,15 +110,11 @@ static void svm_store_cpu_guest_regs(
if ( regs != NULL )
{
- regs->eip = vmcb->rip;
+ regs->ss = vmcb->ss.sel;
regs->esp = vmcb->rsp;
regs->eflags = vmcb->rflags;
regs->cs = vmcb->cs.sel;
- regs->ds = vmcb->ds.sel;
- regs->es = vmcb->es.sel;
- regs->ss = vmcb->ss.sel;
- regs->gs = vmcb->gs.sel;
- regs->fs = vmcb->fs.sel;
+ regs->eip = vmcb->rip;
}
if ( crs != NULL )
@@ -752,28 +748,10 @@ static void svm_init_hypercall_page(stru
*(u16 *)(hypercall_page + (__HYPERVISOR_iret * 32)) = 0x0b0f; /* ud2 */
}
-static void save_svm_cpu_user_regs(struct vcpu *v, struct cpu_user_regs *ctxt)
-{
- struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
-
- ctxt->eax = vmcb->rax;
- ctxt->ss = vmcb->ss.sel;
- ctxt->esp = vmcb->rsp;
- ctxt->eflags = vmcb->rflags;
- ctxt->cs = vmcb->cs.sel;
- ctxt->eip = vmcb->rip;
-
- ctxt->gs = vmcb->gs.sel;
- ctxt->fs = vmcb->fs.sel;
- ctxt->es = vmcb->es.sel;
- ctxt->ds = vmcb->ds.sel;
-}
-
static void svm_load_cpu_guest_regs(struct vcpu *v, struct cpu_user_regs *regs)
{
struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
-
- vmcb->rax = regs->eax;
+
vmcb->ss.sel = regs->ss;
vmcb->rsp = regs->esp;
vmcb->rflags = regs->eflags | 2UL;
@@ -2242,7 +2220,6 @@ asmlinkage void svm_vmexit_handler(struc
int inst_len, rc;
exit_reason = vmcb->exitcode;
- save_svm_cpu_user_regs(v, regs);
HVMTRACE_2D(VMEXIT, v, vmcb->rip, exit_reason);
diff -r e19ddfa781c5 -r 60240a72e2b2 xen/arch/x86/hvm/svm/x86_32/exits.S
--- a/xen/arch/x86/hvm/svm/x86_32/exits.S Thu May 10 22:54:43 2007 +0100
+++ b/xen/arch/x86/hvm/svm/x86_32/exits.S Thu May 10 23:49:04 2007 +0100
@@ -16,6 +16,7 @@
* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*/
+
#include <xen/config.h>
#include <xen/errno.h>
#include <xen/softirq.h>
@@ -25,60 +26,23 @@
#include <public/xen.h>
#define GET_CURRENT(reg) \
- movl $STACK_SIZE-4, reg; \
- orl %esp, reg; \
+ movl $STACK_SIZE-4,reg; \
+ orl %esp,reg; \
andl $~3,reg; \
movl (reg),reg;
-/*
- * At VMExit time the processor saves the guest selectors, esp, eip,
- * and eflags. Therefore we don't save them, but simply decrement
- * the kernel stack pointer to make it consistent with the stack frame
- * at usual interruption time. The eflags of the host is not saved by AMD-V,
- * and we set it to the fixed value.
- *
- * We also need the room, especially because orig_eax field is used
- * by do_IRQ(). Compared the cpu_user_regs, we skip pushing for the following:
- * (10) u32 gs;
- * (9) u32 fs;
- * (8) u32 ds;
- * (7) u32 es;
- * <- get_stack_bottom() (= HOST_ESP)
- * (6) u32 ss;
- * (5) u32 esp;
- * (4) u32 eflags;
- * (3) u32 cs;
- * (2) u32 eip;
- * (2/1) u16 entry_vector;
- * (1/1) u16 error_code;
- * However, get_stack_bottom() actually returns 20 bytes before the real
- * bottom of the stack to allow space for:
- * domain pointer, DS, ES, FS, GS. Therefore, we effectively skip 6 registers.
- */
-
#define HVM_MONITOR_EFLAGS 0x202 /* IF on */
-#define NR_SKIPPED_REGS 6 /* See the above explanation */
-#define HVM_SAVE_ALL_NOSEGREGS \
- pushl $HVM_MONITOR_EFLAGS; \
- popf; \
- subl $(NR_SKIPPED_REGS*4), %esp; \
- pushl %eax; \
- pushl %ebp; \
- pushl %edi; \
- pushl %esi; \
- pushl %edx; \
- pushl %ecx; \
+#define NR_SKIPPED_REGS 7 /* Skip SS thru EAX */
+#define HVM_SAVE_ALL_NOSEGREGS \
+ pushl $HVM_MONITOR_EFLAGS; \
+ popf; \
+ subl $(NR_SKIPPED_REGS*4),%esp; \
+ pushl %ebp; \
+ pushl %edi; \
+ pushl %esi; \
+ pushl %edx; \
+ pushl %ecx; \
pushl %ebx;
-
-#define HVM_RESTORE_ALL_NOSEGREGS \
- popl %ebx; \
- popl %ecx; \
- popl %edx; \
- popl %esi; \
- popl %edi; \
- popl %ebp; \
- popl %eax; \
- addl $(NR_SKIPPED_REGS*4), %esp
#define VMRUN .byte 0x0F,0x01,0xD8
#define VMLOAD .byte 0x0F,0x01,0xDA
@@ -88,12 +52,10 @@
ENTRY(svm_asm_do_resume)
GET_CURRENT(%ebx)
- xorl %ecx,%ecx
- notl %ecx
cli # tests must not race interrupts
movl VCPU_processor(%ebx),%eax
shl $IRQSTAT_shift,%eax
- test %ecx,irq_stat(%eax,1)
+ testl $~0,irq_stat(%eax,1)
jnz svm_process_softirqs
call svm_intr_assist
call svm_load_cr2
@@ -101,39 +63,35 @@ ENTRY(svm_asm_do_resume)
CLGI
sti
GET_CURRENT(%ebx)
- movl VCPU_svm_vmcb(%ebx), %ecx
- movl 24(%esp), %eax
- movl %eax, VMCB_rax(%ecx)
- movl VCPU_processor(%ebx), %eax
- movl root_vmcb_pa(,%eax,8), %eax
+ movl VCPU_svm_vmcb(%ebx),%ecx
+ movl UREGS_eax(%esp),%eax
+ movl %eax,VMCB_rax(%ecx)
+ movl VCPU_processor(%ebx),%eax
+ movl root_vmcb_pa(,%eax,8),%eax
VMSAVE
- movl VCPU_svm_vmcb_pa(%ebx), %eax
+ movl VCPU_svm_vmcb_pa(%ebx),%eax
popl %ebx
popl %ecx
popl %edx
popl %esi
popl %edi
popl %ebp
-
- /*
- * Skip %eax, we need to have vmcb address in there.
- * Don't worry, EAX is restored through the VMRUN instruction.
- */
- addl $4, %esp
- addl $(NR_SKIPPED_REGS*4), %esp
+ addl $(NR_SKIPPED_REGS*4),%esp
VMLOAD
VMRUN
VMSAVE
- /* eax is the only register we're allowed to touch here... */
- GET_CURRENT(%eax)
+ HVM_SAVE_ALL_NOSEGREGS
- movl VCPU_processor(%eax), %eax
- movl root_vmcb_pa(,%eax,8), %eax
+ GET_CURRENT(%ebx)
+ movl VCPU_svm_vmcb(%ebx),%ecx
+ movl VMCB_rax(%ecx),%eax
+ movl %eax,UREGS_eax(%esp)
+ movl VCPU_processor(%ebx),%eax
+ movl root_vmcb_pa(,%eax,8),%eax
VMLOAD
- HVM_SAVE_ALL_NOSEGREGS
STGI
.globl svm_stgi_label;
svm_stgi_label:
diff -r e19ddfa781c5 -r 60240a72e2b2 xen/arch/x86/hvm/svm/x86_64/exits.S
--- a/xen/arch/x86/hvm/svm/x86_64/exits.S Thu May 10 22:54:43 2007 +0100
+++ b/xen/arch/x86/hvm/svm/x86_64/exits.S Thu May 10 23:49:04 2007 +0100
@@ -16,6 +16,7 @@
* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*/
+
#include <xen/config.h>
#include <xen/errno.h>
#include <xen/softirq.h>
@@ -25,72 +26,32 @@
#include <public/xen.h>
#define GET_CURRENT(reg) \
- movq $STACK_SIZE-8, reg; \
- orq %rsp, reg; \
+ movq $STACK_SIZE-8,reg; \
+ orq %rsp,reg; \
andq $~7,reg; \
movq (reg),reg;
-/*
- * At VMExit time the processor saves the guest selectors, rsp, rip,
- * and rflags. Therefore we don't save them, but simply decrement
- * the kernel stack pointer to make it consistent with the stack frame
- * at usual interruption time. The rflags of the host is not saved by AMD-V,
- * and we set it to the fixed value.
- *
- * We also need the room, especially because orig_eax field is used
- * by do_IRQ(). Compared the cpu_user_regs, we skip pushing for the following:
- * (10) u64 gs;
- * (9) u64 fs;
- * (8) u64 ds;
- * (7) u64 es;
- * <- get_stack_bottom() (= HOST_ESP)
- * (6) u64 ss;
- * (5) u64 rsp;
- * (4) u64 rflags;
- * (3) u64 cs;
- * (2) u64 rip;
- * (2/1) u32 entry_vector;
- * (1/1) u32 error_code;
- */
#define HVM_MONITOR_RFLAGS 0x202 /* IF on */
-#define NR_SKIPPED_REGS 6 /* See the above explanation */
-#define HVM_SAVE_ALL_NOSEGREGS \
- pushq $HVM_MONITOR_RFLAGS; \
- popfq; \
- subq $(NR_SKIPPED_REGS*8), %rsp; \
- pushq %rdi; \
- pushq %rsi; \
- pushq %rdx; \
- pushq %rcx; \
- pushq %rax; \
- pushq %r8; \
- pushq %r9; \
- pushq %r10; \
- pushq %r11; \
- pushq %rbx; \
- pushq %rbp; \
- pushq %r12; \
- pushq %r13; \
- pushq %r14; \
- pushq %r15; \
-
-#define HVM_RESTORE_ALL_NOSEGREGS \
- popq %r15; \
- popq %r14; \
- popq %r13; \
- popq %r12; \
- popq %rbp; \
- popq %rbx; \
- popq %r11; \
- popq %r10; \
- popq %r9; \
- popq %r8; \
- popq %rax; \
- popq %rcx; \
- popq %rdx; \
- popq %rsi; \
- popq %rdi; \
- addq $(NR_SKIPPED_REGS*8), %rsp; \
+#define NR_SKIPPED_REGS 6 /* Skip SS thru error_code */
+#define HVM_SAVE_ALL_NOSEGREGS \
+ pushq $HVM_MONITOR_RFLAGS; \
+ popfq; \
+ subq $(NR_SKIPPED_REGS*8),%rsp; \
+ pushq %rdi; \
+ pushq %rsi; \
+ pushq %rdx; \
+ pushq %rcx; \
+ pushq %rax; \
+ pushq %r8; \
+ pushq %r9; \
+ pushq %r10; \
+ pushq %r11; \
+ pushq %rbx; \
+ pushq %rbp; \
+ pushq %r12; \
+ pushq %r13; \
+ pushq %r14; \
+ pushq %r15;
#define VMRUN .byte 0x0F,0x01,0xD8
#define VMLOAD .byte 0x0F,0x01,0xDA
@@ -102,9 +63,9 @@ ENTRY(svm_asm_do_resume)
GET_CURRENT(%rbx)
cli # tests must not race interrupts
movl VCPU_processor(%rbx),%eax
- shl $IRQSTAT_shift, %rax
- leaq irq_stat(%rip), %rdx
- testl $~0, (%rdx, %rax, 1)
+ shl $IRQSTAT_shift,%rax
+ leaq irq_stat(%rip),%rdx
+ testl $~0,(%rdx,%rax,1)
jnz svm_process_softirqs
call svm_intr_assist
call svm_load_cr2
@@ -112,15 +73,15 @@ ENTRY(svm_asm_do_resume)
CLGI
sti
GET_CURRENT(%rbx)
- movq VCPU_svm_vmcb(%rbx), %rcx
- movq UREGS_rax(%rsp), %rax
- movq %rax, VMCB_rax(%rcx)
- leaq root_vmcb_pa(%rip), %rax
- movl VCPU_processor(%rbx), %ecx
- movq (%rax,%rcx,8), %rax
+ movq VCPU_svm_vmcb(%rbx),%rcx
+ movq UREGS_rax(%rsp),%rax
+ movq %rax,VMCB_rax(%rcx)
+ leaq root_vmcb_pa(%rip),%rax
+ movl VCPU_processor(%rbx),%ecx
+ movq (%rax,%rcx,8),%rax
VMSAVE
- movq VCPU_svm_vmcb_pa(%rbx), %rax
+ movq VCPU_svm_vmcb_pa(%rbx),%rax
popq %r15
popq %r14
popq %r13
@@ -131,26 +92,26 @@ ENTRY(svm_asm_do_resume)
popq %r10
popq %r9
popq %r8
- /*
- * Skip %rax, we need to have vmcb address in there.
- * Don't worry, RAX is restored through the VMRUN instruction.
- */
- addq $8, %rsp
+ addq $8,%rsp /* Skip %rax: restored by VMRUN. */
popq %rcx
popq %rdx
popq %rsi
popq %rdi
- addq $(NR_SKIPPED_REGS*8), %rsp
+ addq $(NR_SKIPPED_REGS*8),%rsp
VMLOAD
VMRUN
VMSAVE
+
HVM_SAVE_ALL_NOSEGREGS
GET_CURRENT(%rbx)
- leaq root_vmcb_pa(%rip), %rax
- movl VCPU_processor(%rbx), %ecx
- movq (%rax,%rcx,8), %rax
+ movq VCPU_svm_vmcb(%rbx),%rcx
+ movq VMCB_rax(%rcx),%rax
+ movq %rax,UREGS_rax(%rsp)
+ leaq root_vmcb_pa(%rip),%rax
+ movl VCPU_processor(%rbx),%ecx
+ movq (%rax,%rcx,8),%rax
VMLOAD
STGI
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