diff options
| -rw-r--r-- | arch/x86/include/asm/lguest_hcall.h | 24 | ||||
| -rw-r--r-- | arch/x86/lguest/boot.c | 78 | ||||
| -rw-r--r-- | arch/x86/lguest/i386_head.S | 4 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 7 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 4 | ||||
| -rw-r--r-- | drivers/lguest/x86/core.c | 62 |
6 files changed, 122 insertions, 57 deletions
diff --git a/arch/x86/include/asm/lguest_hcall.h b/arch/x86/include/asm/lguest_hcall.h index 4389442..0f4ee71 100644 --- a/arch/x86/include/asm/lguest_hcall.h +++ b/arch/x86/include/asm/lguest_hcall.h @@ -26,36 +26,20 @@ #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 */ @@ -64,7 +48,7 @@ hcall(unsigned long call, #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__ */ diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 7822d29..5be9293 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -107,7 +107,7 @@ static void async_hcall(unsigned long call, unsigned long arg1, 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; @@ -134,13 +134,32 @@ static void async_hcall(unsigned long call, unsigned long 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); } @@ -150,7 +169,7 @@ static void lazy_hcall(unsigned long call, 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 @@ -229,7 +248,7 @@ static void lguest_write_idt_entry(gate_desc *dt, /* 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 @@ -241,7 +260,7 @@ static void lguest_load_idt(const struct desc_ptr *desc) 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); } /* @@ -261,8 +280,8 @@ static void lguest_load_idt(const struct desc_ptr *desc) */ 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, @@ -272,7 +291,7 @@ static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum, 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 @@ -284,7 +303,7 @@ static void lguest_load_tls(struct thread_struct *t, unsigned int cpu) * 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 @@ -382,7 +401,7 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx, 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; } @@ -396,7 +415,7 @@ static unsigned long lguest_read_cr0(void) * 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; } @@ -418,7 +437,7 @@ static bool cr3_changed = false; 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; } @@ -493,7 +512,7 @@ static void lguest_write_cr4(unsigned long val) 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, @@ -509,8 +528,8 @@ 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 @@ -526,7 +545,7 @@ static void lguest_set_pte(pte_t *ptep, pte_t pteval) { *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 @@ -542,7 +561,7 @@ static void lguest_set_pte(pte_t *ptep, pte_t pteval) 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. @@ -550,7 +569,7 @@ static void lguest_flush_tlb_single(unsigned long addr) * 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 @@ -558,7 +577,7 @@ static void lguest_flush_tlb_user(void) * 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); } /* @@ -695,7 +714,7 @@ static int lguest_clockevent_set_next_event(unsigned long delta, } /* Please wake us this far in the future. */ - hcall(LHCALL_SET_CLOCKEVENT, delta, 0, 0); + kvm_hypercall1(LHCALL_SET_CLOCKEVENT, delta); return 0; } @@ -706,7 +725,7 @@ static void lguest_clockevent_set_mode(enum clock_event_mode mode, 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. */ @@ -781,8 +800,8 @@ static void lguest_time_init(void) 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. */ @@ -855,7 +874,7 @@ static void set_lguest_basic_apic_ops(void) /* 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 @@ -865,7 +884,8 @@ static void lguest_safe_halt(void) * 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); } /* @@ -875,7 +895,7 @@ static void lguest_power_off(void) */ 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; } @@ -916,7 +936,7 @@ static __init int early_put_chars(u32 vtermno, const char *buf, int count) 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; @@ -926,7 +946,7 @@ static __init int early_put_chars(u32 vtermno, const char *buf, int count) * 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 diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S index 10b9bd3..f795419 100644 --- a/arch/x86/lguest/i386_head.S +++ b/arch/x86/lguest/i386_head.S @@ -27,8 +27,8 @@ ENTRY(lguest_entry) /* We make the "initialization" hypercall now to tell the Host about * us, and also find out where it put our page tables. */ movl $LHCALL_LGUEST_INIT, %eax - movl $lguest_data - __PAGE_OFFSET, %edx - int $LGUEST_TRAP_ENTRY + movl $lguest_data - __PAGE_OFFSET, %ebx + .byte 0x0f,0x01,0xc1 /* KVM_HYPERCALL */ /* Set up the initial stack so we can run C code. */ movl $(init_thread_union+THREAD_SIZE),%esp diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 415fab0..504091d 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -288,9 +288,10 @@ static int direct_trap(unsigned int num) /* The Host needs to see page faults (for shadow paging and to save the * fault address), general protection faults (in/out emulation) and - * device not available (TS handling), and of course, the hypercall - * trap. */ - return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY; + * device not available (TS handling), invalid opcode fault (kvm hcall), + * and of course, the hypercall trap. */ + return num != 14 && num != 13 && num != 7 && + num != 6 && num != LGUEST_TRAP_ENTRY; } /*:*/ diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c index 8132533..df44d96 100644 --- a/drivers/lguest/lguest_device.c +++ b/drivers/lguest/lguest_device.c @@ -161,7 +161,7 @@ static void set_status(struct virtio_device *vdev, u8 status) /* We set the status. */ to_lgdev(vdev)->desc->status = status; - hcall(LHCALL_NOTIFY, (max_pfn<<PAGE_SHIFT) + offset, 0, 0); + kvm_hypercall1(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset); } static void lg_set_status(struct virtio_device *vdev, u8 status) @@ -209,7 +209,7 @@ static void lg_notify(struct virtqueue *vq) * virtqueue structure. */ struct lguest_vq_info *lvq = vq->priv; - hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0); + kvm_hypercall1(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT); } /* An extern declaration inside a C file is bad form. Don't do it. */ diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index bf79423..a6b7176 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -290,6 +290,57 @@ static int emulate_insn(struct lg_cpu *cpu) 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) { @@ -337,7 +388,7 @@ 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(); @@ -347,6 +398,15 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu) * 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. */ |
