Re: [patch] KVM: add MSR based hypercall API

Ingo Molnar
2007-01-09T14:38:32Z

* Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:

> > so i'd vote for the 64-bit natural register order: return value in
> > rax, parameters in: rdi, rsi, rdx, rcx, r8, r9. On 32-bit that would
> > be edi, esi, edx, ecx, ebx, ebp - the last two shuffled into
> > VCPU_REGS_R8/R9. That's 6 parameters already - should be enough -
> > that's what Linux has itself. Whatever else must be passed in should
> > come pointer-passed.
>
> Agreed, let's make it so. When you say "pointer-passed" you mean
> physical address passed, right? ;-)

yeah ;)

/me whistles

below is the current snapshot (ontop of tarball).

Ingo

Index: linux/arch/i386/kernel/paravirt.c
===================================================================
--- linux.orig/arch/i386/kernel/paravirt.c
+++ linux/arch/i386/kernel/paravirt.c
@@ -888,29 +888,40 @@ asm (
" ret \n"
);

-extern unsigned char hypercall_addr[4];
+extern unsigned char hypercall_addr[6];

-
-static inline int
-kvm_hypercall(void *param1, void *param2, void *param3, void *param4)
-{
- int ret = -1;
-
- asm (" call hypercall_addr\n"
- : "=g" (ret)
- : "eax" (param1),
- "ecx" (param2),
- "edx" (param3),
- "ebp" (param4));
-
- return ret;
-}
+#define hypercall0(nr) \
+({ \
+ int __ret; \
+ \
+ asm (" call hypercall_addr\n" \
+ : "=a" (__ret) \
+ : "a" (nr) \
+ ); \
+ __ret; \
+})
+
+#define hypercall1(nr, p1) \
+({ \
+ int __ret; \
+ \
+ asm (" call hypercall_addr\n" \
+ : "=a" (__ret) \
+ : "a" (nr), \
+ "D" (p1) \
+ ); \
+ __ret; \
+})

void test_hypercall(void)
{
- int ret = kvm_hypercall((void *)1, (void *)2, (void *)3, (void *)4);
+ int ret;
+
+ ret = hypercall0(__NR_hypercall_load_cr3);
+ printk(KERN_DEBUG "hypercall test #1, ret: %d\n", ret);

- printk(KERN_DEBUG "hypercall test, ret: %d\n", ret);
+ ret = hypercall1(0xbad, 0xbad);
+ printk(KERN_DEBUG "hypercall test #2, ret: %d\n", ret);
}

int kvm_guest_register_para(int cpu)
Index: linux/drivers/kvm/kvm.h
===================================================================
--- linux.orig/drivers/kvm/kvm.h
+++ linux/drivers/kvm/kvm.h
@@ -639,4 +639,6 @@ static inline u32 get_rdx_init_val(void)
#define TSS_REDIRECTION_SIZE (256 / 8)
#define RMODE_TSS_SIZE (TSS_BASE_SIZE + TSS_REDIRECTION_SIZE + TSS_IOPB_SIZE + 1)

+extern int kvm_handle_hypercall(struct kvm_vcpu *vcpu);
+
#endif
Index: linux/drivers/kvm/kvm_main.c
===================================================================
--- linux.orig/drivers/kvm/kvm_main.c
+++ linux/drivers/kvm/kvm_main.c
@@ -1138,6 +1138,32 @@ int emulate_instruction(struct kvm_vcpu
}
EXPORT_SYMBOL_GPL(emulate_instruction);

+int hypercall_load_cr3(struct kvm_vcpu *vcpu, unsigned long new_cr3)
+{
+ printk("not yet\n");
+
+ return -ENOSYS;
+}
+
+int kvm_handle_hypercall(struct kvm_vcpu *vcpu)
+{
+ int nr = vcpu->regs[VCPU_REGS_RAX];
+ int ret = -EINVAL;
+
+ switch (nr) {
+ case __NR_hypercall_load_cr3:
+
+ ret = hypercall_load_cr3(vcpu, vcpu->regs[VCPU_REGS_RDI]);
+ break;
+ default:
+ printk(KERN_DEBUG "invalid hypercall %d\n", nr);
+ }
+ vcpu->regs[VCPU_REGS_RAX] = ret;
+
+ return 1;
+}
+EXPORT_SYMBOL_GPL(kvm_handle_hypercall);
+
static u64 mk_cr_64(u64 curr_cr, u32 new_val)
{
return (curr_cr & ~((1ULL << 32) - 1)) | new_val;
Index: linux/drivers/kvm/vmx.c
===================================================================
--- linux.orig/drivers/kvm/vmx.c
+++ linux/drivers/kvm/vmx.c
@@ -1032,7 +1032,7 @@ static int vmcs_setup_cr3_cache(struct k
cr3_target_values = (msr_val >> 16) & ((1 << 10) - 1);
printk(KERN_DEBUG " cr3 target values: %d\n", cr3_target_values);
if (cr3_target_values > KVM_CR3_CACHE_SIZE) {
- printk(KERN_WARN "KVM: limiting cr3 cache size from %d to %d\n",
+ printk(KERN_WARNING "KVM: limiting cr3 cache size from %d to %d\n",
cr3_target_values, KVM_CR3_CACHE_SIZE);
cr3_target_values = KVM_CR3_CACHE_SIZE;
}
@@ -1726,16 +1726,12 @@ static int handle_halt(struct kvm_vcpu *
static int handle_vmcall(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
kvm_run->exit_reason = KVM_EXIT_DEBUG;
- printk(KERN_DEBUG "got vmcall at RIP %08lx\n", vmcs_readl(GUEST_RIP));
- printk(KERN_DEBUG "vmcall params: %08lx, %08lx, %08lx, %08lx\n",
- vcpu->regs[VCPU_REGS_RAX],
- vcpu->regs[VCPU_REGS_RCX],
- vcpu->regs[VCPU_REGS_RDX],
- vcpu->regs[VCPU_REGS_RBP]);
- vcpu->regs[VCPU_REGS_RAX] = 0;
+ kvm_handle_hypercall(vcpu);
vmcs_writel(GUEST_RIP, vmcs_readl(GUEST_RIP)+3);
+
return 1;
}
+
/*
* The exit handlers return 1 if the exit was handled fully and guest execution
* may resume. Otherwise they set the kvm_run parameter to indicate what needs
Index: linux/include/linux/kvm_para.h
===================================================================
--- linux.orig/include/linux/kvm_para.h
+++ linux/include/linux/kvm_para.h
@@ -72,4 +72,19 @@ struct kvm_vcpu_para_state {

#define KVM_EINVAL EINVAL

+/*
+ * Hypercall calling convention:
+ *
+ * RAX is the hypercall index, goes from 0 to __NR_hypercalls-1
+ *
+ * Each hypercall may have 0-6 parameters.
+ *
+ * parameters 1-6 are in the standard gcc x86_64 calling convention
+ * order: RDI, RSI, RDX, RCX, R8, R9.
+ *
+ * 32-bit parameters are: EDI, ESI, EDX, ECX, EBX, EBP
+ */
+#define __NR_hypercall_load_cr3 0
+#define __NR_hypercalls 1
+
#endif