#ifndef __ASSEMBLY__
#include <asm/hw_irq.h>
+#include <asm/kvm_para.h>
/*G:031 But first, how does our Guest contact the Host to ask for privileged
* operations? There are two ways: the direct way is to make a "hypercall",
* to make requests of the Host Itself.
*
- * Our hypercall mechanism uses the highest unused trap code (traps 32 and
- * above are used by real hardware interrupts). Fifteen hypercalls are
+ * We use the KVM hypercall mechanism. Eighteen hypercalls are
* available: the hypercall number is put in the %eax register, and the
- * arguments (when required) are placed in %edx, %ebx and %ecx. If a return
+ * arguments (when required) are placed in %ebx, %ecx and %edx. If a return
* value makes sense, it's returned in %eax.
*
* Grossly invalid calls result in Sudden Death at the hands of the vengeful
* Host, rather than returning failure. This reflects Winston Churchill's
* definition of a gentleman: "someone who is only rude intentionally". */
-static inline unsigned long
-hcall(unsigned long call,
- unsigned long arg1, unsigned long arg2, unsigned long arg3)
-{
- /* "int" is the Intel instruction to trigger a trap. */
- asm volatile("int $" __stringify(LGUEST_TRAP_ENTRY)
- /* The call in %eax (aka "a") might be overwritten */
- : "=a"(call)
- /* The arguments are in %eax, %edx, %ebx & %ecx */
- : "a"(call), "d"(arg1), "b"(arg2), "c"(arg3)
- /* "memory" means this might write somewhere in memory.
- * This isn't true for all calls, but it's safe to tell
- * gcc that it might happen so it doesn't get clever. */
- : "memory");
- return call;
-}
/*:*/
/* Can't use our min() macro here: needs to be a constant */
#define LHCALL_RING_SIZE 64
struct hcall_args {
/* These map directly onto eax, ebx, ecx, edx in struct lguest_regs */
- unsigned long arg0, arg2, arg3, arg1;
+ unsigned long arg0, arg1, arg2, arg3;
};
#endif /* !__ASSEMBLY__ */
local_irq_save(flags);
if (lguest_data.hcall_status[next_call] != 0xFF) {
/* Table full, so do normal hcall which will flush table. */
- hcall(call, arg1, arg2, arg3);
+ kvm_hypercall3(call, arg1, arg2, arg3);
} else {
lguest_data.hcalls[next_call].arg0 = call;
lguest_data.hcalls[next_call].arg1 = arg1;
*
* So, when we're in lazy mode, we call async_hcall() to store the call for
* future processing: */
-static void lazy_hcall(unsigned long call,
+static void lazy_hcall1(unsigned long call,
+ unsigned long arg1)
+{
+ if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE)
+ kvm_hypercall1(call, arg1);
+ else
+ async_hcall(call, arg1, 0, 0);
+}
+
+static void lazy_hcall2(unsigned long call,
+ unsigned long arg1,
+ unsigned long arg2)
+{
+ if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE)
+ kvm_hypercall2(call, arg1, arg2);
+ else
+ async_hcall(call, arg1, arg2, 0);
+}
+
+static void lazy_hcall3(unsigned long call,
unsigned long arg1,
unsigned long arg2,
unsigned long arg3)
{
if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE)
- hcall(call, arg1, arg2, arg3);
+ kvm_hypercall3(call, arg1, arg2, arg3);
else
async_hcall(call, arg1, arg2, arg3);
}
static void lguest_leave_lazy_mode(void)
{
paravirt_leave_lazy(paravirt_get_lazy_mode());
- hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
+ kvm_hypercall0(LHCALL_FLUSH_ASYNC);
}
/*G:033
/* Keep the local copy up to date. */
native_write_idt_entry(dt, entrynum, g);
/* Tell Host about this new entry. */
- hcall(LHCALL_LOAD_IDT_ENTRY, entrynum, desc[0], desc[1]);
+ kvm_hypercall3(LHCALL_LOAD_IDT_ENTRY, entrynum, desc[0], desc[1]);
}
/* Changing to a different IDT is very rare: we keep the IDT up-to-date every
struct desc_struct *idt = (void *)desc->address;
for (i = 0; i < (desc->size+1)/8; i++)
- hcall(LHCALL_LOAD_IDT_ENTRY, i, idt[i].a, idt[i].b);
+ kvm_hypercall3(LHCALL_LOAD_IDT_ENTRY, i, idt[i].a, idt[i].b);
}
/*
*/
static void lguest_load_gdt(const struct desc_ptr *desc)
{
- BUG_ON((desc->size+1)/8 != GDT_ENTRIES);
- hcall(LHCALL_LOAD_GDT, __pa(desc->address), GDT_ENTRIES, 0);
+ BUG_ON((desc->size + 1) / 8 != GDT_ENTRIES);
+ kvm_hypercall2(LHCALL_LOAD_GDT, __pa(desc->address), GDT_ENTRIES);
}
/* For a single GDT entry which changes, we do the lazy thing: alter our GDT,
const void *desc, int type)
{
native_write_gdt_entry(dt, entrynum, desc, type);
- hcall(LHCALL_LOAD_GDT, __pa(dt), GDT_ENTRIES, 0);
+ kvm_hypercall2(LHCALL_LOAD_GDT, __pa(dt), GDT_ENTRIES);
}
/* OK, I lied. There are three "thread local storage" GDT entries which change
* can't handle us removing entries we're currently using. So we clear
* the GS register here: if it's needed it'll be reloaded anyway. */
lazy_load_gs(0);
- lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0);
+ lazy_hcall2(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu);
}
/*G:038 That's enough excitement for now, back to ploughing through each of
static unsigned long current_cr0;
static void lguest_write_cr0(unsigned long val)
{
- lazy_hcall(LHCALL_TS, val & X86_CR0_TS, 0, 0);
+ lazy_hcall1(LHCALL_TS, val & X86_CR0_TS);
current_cr0 = val;
}
* the vowels have been optimized out. */
static void lguest_clts(void)
{
- lazy_hcall(LHCALL_TS, 0, 0, 0);
+ lazy_hcall1(LHCALL_TS, 0);
current_cr0 &= ~X86_CR0_TS;
}
static void lguest_write_cr3(unsigned long cr3)
{
lguest_data.pgdir = cr3;
- lazy_hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0);
+ lazy_hcall1(LHCALL_NEW_PGTABLE, cr3);
cr3_changed = true;
}
static void lguest_pte_update(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
- lazy_hcall(LHCALL_SET_PTE, __pa(mm->pgd), addr, ptep->pte_low);
+ lazy_hcall3(LHCALL_SET_PTE, __pa(mm->pgd), addr, ptep->pte_low);
}
static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr,
static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
{
*pmdp = pmdval;
- lazy_hcall(LHCALL_SET_PMD, __pa(pmdp)&PAGE_MASK,
- (__pa(pmdp)&(PAGE_SIZE-1))/4, 0);
+ lazy_hcall2(LHCALL_SET_PMD, __pa(pmdp) & PAGE_MASK,
+ (__pa(pmdp) & (PAGE_SIZE - 1)) / 4);
}
/* There are a couple of legacy places where the kernel sets a PTE, but we
{
*ptep = pteval;
if (cr3_changed)
- lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
+ lazy_hcall1(LHCALL_FLUSH_TLB, 1);
}
/* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
static void lguest_flush_tlb_single(unsigned long addr)
{
/* Simply set it to zero: if it was not, it will fault back in. */
- lazy_hcall(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
+ lazy_hcall3(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
}
/* This is what happens after the Guest has removed a large number of entries.
* have changed, ie. virtual addresses below PAGE_OFFSET. */
static void lguest_flush_tlb_user(void)
{
- lazy_hcall(LHCALL_FLUSH_TLB, 0, 0, 0);
+ lazy_hcall1(LHCALL_FLUSH_TLB, 0);
}
/* This is called when the kernel page tables have changed. That's not very
* slow), so it's worth separating this from the user flushing above. */
static void lguest_flush_tlb_kernel(void)
{
- lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
+ lazy_hcall1(LHCALL_FLUSH_TLB, 1);
}
/*
}
/* Please wake us this far in the future. */
- hcall(LHCALL_SET_CLOCKEVENT, delta, 0, 0);
+ kvm_hypercall1(LHCALL_SET_CLOCKEVENT, delta);
return 0;
}
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
/* A 0 argument shuts the clock down. */
- hcall(LHCALL_SET_CLOCKEVENT, 0, 0, 0);
+ kvm_hypercall0(LHCALL_SET_CLOCKEVENT);
break;
case CLOCK_EVT_MODE_ONESHOT:
/* This is what we expect. */
static void lguest_load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
{
- lazy_hcall(LHCALL_SET_STACK, __KERNEL_DS|0x1, thread->sp0,
- THREAD_SIZE/PAGE_SIZE);
+ lazy_hcall3(LHCALL_SET_STACK, __KERNEL_DS | 0x1, thread->sp0,
+ THREAD_SIZE / PAGE_SIZE);
}
/* Let's just say, I wouldn't do debugging under a Guest. */
/* STOP! Until an interrupt comes in. */
static void lguest_safe_halt(void)
{
- hcall(LHCALL_HALT, 0, 0, 0);
+ kvm_hypercall0(LHCALL_HALT);
}
/* The SHUTDOWN hypercall takes a string to describe what's happening, and
* rather than virtual addresses, so we use __pa() here. */
static void lguest_power_off(void)
{
- hcall(LHCALL_SHUTDOWN, __pa("Power down"), LGUEST_SHUTDOWN_POWEROFF, 0);
+ kvm_hypercall2(LHCALL_SHUTDOWN, __pa("Power down"),
+ LGUEST_SHUTDOWN_POWEROFF);
}
/*
*/
static int lguest_panic(struct notifier_block *nb, unsigned long l, void *p)
{
- hcall(LHCALL_SHUTDOWN, __pa(p), LGUEST_SHUTDOWN_POWEROFF, 0);
+ kvm_hypercall2(LHCALL_SHUTDOWN, __pa(p), LGUEST_SHUTDOWN_POWEROFF);
/* The hcall won't return, but to keep gcc happy, we're "done". */
return NOTIFY_DONE;
}
len = sizeof(scratch) - 1;
scratch[len] = '\0';
memcpy(scratch, buf, len);
- hcall(LHCALL_NOTIFY, __pa(scratch), 0, 0);
+ kvm_hypercall1(LHCALL_NOTIFY, __pa(scratch));
/* This routine returns the number of bytes actually written. */
return len;
* Launcher to reboot us. */
static void lguest_restart(char *reason)
{
- hcall(LHCALL_SHUTDOWN, __pa(reason), LGUEST_SHUTDOWN_RESTART, 0);
+ kvm_hypercall2(LHCALL_SHUTDOWN, __pa(reason), LGUEST_SHUTDOWN_RESTART);
}
/*G:050
return 1;
}
+/* Our hypercalls mechanism used to be based on direct software interrupts.
+ * After Anthony's "Refactor hypercall infrastructure" kvm patch, we decided to
+ * change over to using kvm hypercalls.
+ *
+ * KVM_HYPERCALL is actually a "vmcall" instruction, which generates an invalid
+ * opcode fault (fault 6) on non-VT cpus, so the easiest solution seemed to be
+ * an *emulation approach*: if the fault was really produced by an hypercall
+ * (is_hypercall() does exactly this check), we can just call the corresponding
+ * hypercall host implementation function.
+ *
+ * But these invalid opcode faults are notably slower than software interrupts.
+ * So we implemented the *patching (or rewriting) approach*: every time we hit
+ * the KVM_HYPERCALL opcode in Guest code, we patch it to the old "int 0x1f"
+ * opcode, so next time the Guest calls this hypercall it will use the
+ * faster trap mechanism.
+ *
+ * Matias even benchmarked it to convince you: this shows the average cycle
+ * cost of a hypercall. For each alternative solution mentioned above we've
+ * made 5 runs of the benchmark:
+ *
+ * 1) direct software interrupt: 2915, 2789, 2764, 2721, 2898
+ * 2) emulation technique: 3410, 3681, 3466, 3392, 3780
+ * 3) patching (rewrite) technique: 2977, 2975, 2891, 2637, 2884
+ *
+ * One two-line function is worth a 20% hypercall speed boost!
+ */
+static void rewrite_hypercall(struct lg_cpu *cpu)
+{
+ /* This are the opcodes we use to patch the Guest. The opcode for "int
+ * $0x1f" is "0xcd 0x1f" but vmcall instruction is 3 bytes long, so we
+ * complete the sequence with a NOP (0x90). */
+ u8 insn[3] = {0xcd, 0x1f, 0x90};
+
+ __lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn));
+}
+
+static bool is_hypercall(struct lg_cpu *cpu)
+{
+ u8 insn[3];
+
+ /* This must be the Guest kernel trying to do something.
+ * The bottom two bits of the CS segment register are the privilege
+ * level. */
+ if ((cpu->regs->cs & 3) != GUEST_PL)
+ return false;
+
+ /* Is it a vmcall? */
+ __lgread(cpu, insn, guest_pa(cpu, cpu->regs->eip), sizeof(insn));
+ return insn[0] == 0x0f && insn[1] == 0x01 && insn[2] == 0xc1;
+}
+
/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */
void lguest_arch_handle_trap(struct lg_cpu *cpu)
{
break;
case 32 ... 255:
/* These values mean a real interrupt occurred, in which case
- * the Host handler has already been run. We just do a
+ * the Host handler has already been run. We just do a
* friendly check if another process should now be run, then
* return to run the Guest again */
cond_resched();
* up the pointer now to indicate a hypercall is pending. */
cpu->hcall = (struct hcall_args *)cpu->regs;
return;
+ case 6:
+ /* kvm hypercalls trigger an invalid opcode fault (6).
+ * We need to check if ring == GUEST_PL and
+ * faulting instruction == vmcall. */
+ if (is_hypercall(cpu)) {
+ rewrite_hypercall(cpu);
+ return;
+ }
+ break;
}
/* We didn't handle the trap, so it needs to go to the Guest. */
projects / platform / kernel / linux-rpi.git / commitdiff