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linux/arch/mips/kvm/mmu.c
James Hogan 9078210ef4 KVM: MIPS: Fix lazy user ASID regenerate for SMP 
kvm_mips_check_asids() runs before entering the guest and performs lazy
regeneration of host ASID for guest usermode, using last_user_gasid to
track the last guest ASID in the VCPU that was used by guest usermode on
any host CPU.

last_user_gasid is reset after performing the lazy ASID regeneration on
the current CPU, and by kvm_arch_vcpu_load() if the host ASID for guest
usermode is regenerated due to staleness (to cancel outstanding lazy
ASID regenerations). Unfortunately neither case handles SMP hosts
correctly:

 - When the lazy ASID regeneration is performed it should apply to all
   CPUs (as last_user_gasid does), so reset the ASID on other CPUs to
   zero to trigger regeneration when the VCPU is next loaded on those
   CPUs.

 - When the ASID is found to be stale on the current CPU, we should not
   cancel lazy ASID regenerations globally, so drop the reset of
   last_user_gasid altogether here.

Both cases would require a guest ASID change and two host CPU migrations
(and in the latter case one of the CPUs to start a new ASID cycle)
before guest usermode could potentially access stale user pages from a
previously running ASID in the same VCPU.

Fixes: 25b08c7fb0 ("KVM: MIPS: Invalidate TLB by regenerating ASIDs")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-10-26 13:43:41 +02:00

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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* KVM/MIPS MMU handling in the KVM module.
*
* Copyright (C) 2012 MIPS Technologies, Inc. All rights reserved.
* Authors: Sanjay Lal <sanjayl@kymasys.com>
*/
#include <linux/highmem.h>
#include <linux/kvm_host.h>
#include <asm/mmu_context.h>
static u32 kvm_mips_get_kernel_asid(struct kvm_vcpu *vcpu)
{
int cpu = smp_processor_id();
return vcpu->arch.guest_kernel_asid[cpu] &
cpu_asid_mask(&cpu_data[cpu]);
}
static u32 kvm_mips_get_user_asid(struct kvm_vcpu *vcpu)
{
int cpu = smp_processor_id();
return vcpu->arch.guest_user_asid[cpu] &
cpu_asid_mask(&cpu_data[cpu]);
}
static int kvm_mips_map_page(struct kvm *kvm, gfn_t gfn)
{
int srcu_idx, err = 0;
kvm_pfn_t pfn;
if (kvm->arch.guest_pmap[gfn] != KVM_INVALID_PAGE)
return 0;
srcu_idx = srcu_read_lock(&kvm->srcu);
pfn = gfn_to_pfn(kvm, gfn);
if (is_error_noslot_pfn(pfn)) {
kvm_err("Couldn't get pfn for gfn %#llx!\n", gfn);
err = -EFAULT;
goto out;
}
kvm->arch.guest_pmap[gfn] = pfn;
out:
srcu_read_unlock(&kvm->srcu, srcu_idx);
return err;
}
/* Translate guest KSEG0 addresses to Host PA */
unsigned long kvm_mips_translate_guest_kseg0_to_hpa(struct kvm_vcpu *vcpu,
unsigned long gva)
{
gfn_t gfn;
unsigned long offset = gva & ~PAGE_MASK;
struct kvm *kvm = vcpu->kvm;
if (KVM_GUEST_KSEGX(gva) != KVM_GUEST_KSEG0) {
kvm_err("%s/%p: Invalid gva: %#lx\n", __func__,
__builtin_return_address(0), gva);
return KVM_INVALID_PAGE;
}
gfn = (KVM_GUEST_CPHYSADDR(gva) >> PAGE_SHIFT);
if (gfn >= kvm->arch.guest_pmap_npages) {
kvm_err("%s: Invalid gfn: %#llx, GVA: %#lx\n", __func__, gfn,
gva);
return KVM_INVALID_PAGE;
}
if (kvm_mips_map_page(vcpu->kvm, gfn) < 0)
return KVM_INVALID_ADDR;
return (kvm->arch.guest_pmap[gfn] << PAGE_SHIFT) + offset;
}
/* XXXKYMA: Must be called with interrupts disabled */
int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
struct kvm_vcpu *vcpu)
{
gfn_t gfn;
kvm_pfn_t pfn0, pfn1;
unsigned long vaddr = 0;
unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0;
struct kvm *kvm = vcpu->kvm;
const int flush_dcache_mask = 0;
int ret;
if (KVM_GUEST_KSEGX(badvaddr) != KVM_GUEST_KSEG0) {
kvm_err("%s: Invalid BadVaddr: %#lx\n", __func__, badvaddr);
kvm_mips_dump_host_tlbs();
return -1;
}
gfn = (KVM_GUEST_CPHYSADDR(badvaddr) >> PAGE_SHIFT);
if ((gfn | 1) >= kvm->arch.guest_pmap_npages) {
kvm_err("%s: Invalid gfn: %#llx, BadVaddr: %#lx\n", __func__,
gfn, badvaddr);
kvm_mips_dump_host_tlbs();
return -1;
}
vaddr = badvaddr & (PAGE_MASK << 1);
if (kvm_mips_map_page(vcpu->kvm, gfn) < 0)
return -1;
if (kvm_mips_map_page(vcpu->kvm, gfn ^ 0x1) < 0)
return -1;
pfn0 = kvm->arch.guest_pmap[gfn & ~0x1];
pfn1 = kvm->arch.guest_pmap[gfn | 0x1];
entrylo0 = mips3_paddr_to_tlbpfn(pfn0 << PAGE_SHIFT) |
((_page_cachable_default >> _CACHE_SHIFT) << ENTRYLO_C_SHIFT) |
ENTRYLO_D | ENTRYLO_V;
entrylo1 = mips3_paddr_to_tlbpfn(pfn1 << PAGE_SHIFT) |
((_page_cachable_default >> _CACHE_SHIFT) << ENTRYLO_C_SHIFT) |
ENTRYLO_D | ENTRYLO_V;
preempt_disable();
entryhi = (vaddr | kvm_mips_get_kernel_asid(vcpu));
ret = kvm_mips_host_tlb_write(vcpu, entryhi, entrylo0, entrylo1,
flush_dcache_mask);
preempt_enable();
return ret;
}
int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
struct kvm_mips_tlb *tlb)
{
unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0;
struct kvm *kvm = vcpu->kvm;
kvm_pfn_t pfn0, pfn1;
gfn_t gfn0, gfn1;
long tlb_lo[2];
int ret;
tlb_lo[0] = tlb->tlb_lo[0];
tlb_lo[1] = tlb->tlb_lo[1];
/*
* The commpage address must not be mapped to anything else if the guest
* TLB contains entries nearby, or commpage accesses will break.
*/
if (!((tlb->tlb_hi ^ KVM_GUEST_COMMPAGE_ADDR) &
VPN2_MASK & (PAGE_MASK << 1)))
tlb_lo[(KVM_GUEST_COMMPAGE_ADDR >> PAGE_SHIFT) & 1] = 0;
gfn0 = mips3_tlbpfn_to_paddr(tlb_lo[0]) >> PAGE_SHIFT;
gfn1 = mips3_tlbpfn_to_paddr(tlb_lo[1]) >> PAGE_SHIFT;
if (gfn0 >= kvm->arch.guest_pmap_npages ||
gfn1 >= kvm->arch.guest_pmap_npages) {
kvm_err("%s: Invalid gfn: [%#llx, %#llx], EHi: %#lx\n",
__func__, gfn0, gfn1, tlb->tlb_hi);
kvm_mips_dump_guest_tlbs(vcpu);
return -1;
}
if (kvm_mips_map_page(kvm, gfn0) < 0)
return -1;
if (kvm_mips_map_page(kvm, gfn1) < 0)
return -1;
pfn0 = kvm->arch.guest_pmap[gfn0];
pfn1 = kvm->arch.guest_pmap[gfn1];
/* Get attributes from the Guest TLB */
entrylo0 = mips3_paddr_to_tlbpfn(pfn0 << PAGE_SHIFT) |
((_page_cachable_default >> _CACHE_SHIFT) << ENTRYLO_C_SHIFT) |
(tlb_lo[0] & ENTRYLO_D) |
(tlb_lo[0] & ENTRYLO_V);
entrylo1 = mips3_paddr_to_tlbpfn(pfn1 << PAGE_SHIFT) |
((_page_cachable_default >> _CACHE_SHIFT) << ENTRYLO_C_SHIFT) |
(tlb_lo[1] & ENTRYLO_D) |
(tlb_lo[1] & ENTRYLO_V);
kvm_debug("@ %#lx tlb_lo0: 0x%08lx tlb_lo1: 0x%08lx\n", vcpu->arch.pc,
tlb->tlb_lo[0], tlb->tlb_lo[1]);
preempt_disable();
entryhi = (tlb->tlb_hi & VPN2_MASK) | (KVM_GUEST_KERNEL_MODE(vcpu) ?
kvm_mips_get_kernel_asid(vcpu) :
kvm_mips_get_user_asid(vcpu));
ret = kvm_mips_host_tlb_write(vcpu, entryhi, entrylo0, entrylo1,
tlb->tlb_mask);
preempt_enable();
return ret;
}
void kvm_get_new_mmu_context(struct mm_struct *mm, unsigned long cpu,
struct kvm_vcpu *vcpu)
{
unsigned long asid = asid_cache(cpu);
asid += cpu_asid_inc();
if (!(asid & cpu_asid_mask(&cpu_data[cpu]))) {
if (cpu_has_vtag_icache)
flush_icache_all();
kvm_local_flush_tlb_all(); /* start new asid cycle */
if (!asid) /* fix version if needed */
asid = asid_first_version(cpu);
}
cpu_context(cpu, mm) = asid_cache(cpu) = asid;
}
/**
* kvm_mips_migrate_count() - Migrate timer.
* @vcpu: Virtual CPU.
*
* Migrate CP0_Count hrtimer to the current CPU by cancelling and restarting it
* if it was running prior to being cancelled.
*
* Must be called when the VCPU is migrated to a different CPU to ensure that
* timer expiry during guest execution interrupts the guest and causes the
* interrupt to be delivered in a timely manner.
*/
static void kvm_mips_migrate_count(struct kvm_vcpu *vcpu)
{
if (hrtimer_cancel(&vcpu->arch.comparecount_timer))
hrtimer_restart(&vcpu->arch.comparecount_timer);
}
/* Restore ASID once we are scheduled back after preemption */
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
unsigned long asid_mask = cpu_asid_mask(&cpu_data[cpu]);
unsigned long flags;
int newasid = 0;
kvm_debug("%s: vcpu %p, cpu: %d\n", __func__, vcpu, cpu);
/* Allocate new kernel and user ASIDs if needed */
local_irq_save(flags);
if ((vcpu->arch.guest_kernel_asid[cpu] ^ asid_cache(cpu)) &
asid_version_mask(cpu)) {
kvm_get_new_mmu_context(&vcpu->arch.guest_kernel_mm, cpu, vcpu);
vcpu->arch.guest_kernel_asid[cpu] =
vcpu->arch.guest_kernel_mm.context.asid[cpu];
newasid++;
kvm_debug("[%d]: cpu_context: %#lx\n", cpu,
cpu_context(cpu, current->mm));
kvm_debug("[%d]: Allocated new ASID for Guest Kernel: %#x\n",
cpu, vcpu->arch.guest_kernel_asid[cpu]);
}
if ((vcpu->arch.guest_user_asid[cpu] ^ asid_cache(cpu)) &
asid_version_mask(cpu)) {
kvm_get_new_mmu_context(&vcpu->arch.guest_user_mm, cpu, vcpu);
vcpu->arch.guest_user_asid[cpu] =
vcpu->arch.guest_user_mm.context.asid[cpu];
newasid++;
kvm_debug("[%d]: cpu_context: %#lx\n", cpu,
cpu_context(cpu, current->mm));
kvm_debug("[%d]: Allocated new ASID for Guest User: %#x\n", cpu,
vcpu->arch.guest_user_asid[cpu]);
}
if (vcpu->arch.last_sched_cpu != cpu) {
kvm_debug("[%d->%d]KVM VCPU[%d] switch\n",
vcpu->arch.last_sched_cpu, cpu, vcpu->vcpu_id);
/*
* Migrate the timer interrupt to the current CPU so that it
* always interrupts the guest and synchronously triggers a
* guest timer interrupt.
*/
kvm_mips_migrate_count(vcpu);
}
if (!newasid) {
/*
* If we preempted while the guest was executing, then reload
* the pre-empted ASID
*/
if (current->flags & PF_VCPU) {
write_c0_entryhi(vcpu->arch.
preempt_entryhi & asid_mask);
ehb();
}
} else {
/* New ASIDs were allocated for the VM */
/*
* Were we in guest context? If so then the pre-empted ASID is
* no longer valid, we need to set it to what it should be based
* on the mode of the Guest (Kernel/User)
*/
if (current->flags & PF_VCPU) {
if (KVM_GUEST_KERNEL_MODE(vcpu))
write_c0_entryhi(vcpu->arch.
guest_kernel_asid[cpu] &
asid_mask);
else
write_c0_entryhi(vcpu->arch.
guest_user_asid[cpu] &
asid_mask);
ehb();
}
}
/* restore guest state to registers */
kvm_mips_callbacks->vcpu_set_regs(vcpu);
local_irq_restore(flags);
}
/* ASID can change if another task is scheduled during preemption */
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
unsigned long flags;
int cpu;
local_irq_save(flags);
cpu = smp_processor_id();
vcpu->arch.preempt_entryhi = read_c0_entryhi();
vcpu->arch.last_sched_cpu = cpu;
/* save guest state in registers */
kvm_mips_callbacks->vcpu_get_regs(vcpu);
if (((cpu_context(cpu, current->mm) ^ asid_cache(cpu)) &
asid_version_mask(cpu))) {
kvm_debug("%s: Dropping MMU Context: %#lx\n", __func__,
cpu_context(cpu, current->mm));
drop_mmu_context(current->mm, cpu);
}
write_c0_entryhi(cpu_asid(cpu, current->mm));
ehb();
local_irq_restore(flags);
}
u32 kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu)
{
struct mips_coproc *cop0 = vcpu->arch.cop0;
unsigned long paddr, flags, vpn2, asid;
unsigned long va = (unsigned long)opc;
void *vaddr;
u32 inst;
int index;
if (KVM_GUEST_KSEGX(va) < KVM_GUEST_KSEG0 ||
KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG23) {
local_irq_save(flags);
index = kvm_mips_host_tlb_lookup(vcpu, va);
if (index >= 0) {
inst = *(opc);
} else {
vpn2 = va & VPN2_MASK;
asid = kvm_read_c0_guest_entryhi(cop0) &
KVM_ENTRYHI_ASID;
index = kvm_mips_guest_tlb_lookup(vcpu, vpn2 | asid);
if (index < 0) {
kvm_err("%s: get_user_failed for %p, vcpu: %p, ASID: %#lx\n",
__func__, opc, vcpu, read_c0_entryhi());
kvm_mips_dump_host_tlbs();
kvm_mips_dump_guest_tlbs(vcpu);
local_irq_restore(flags);
return KVM_INVALID_INST;
}
if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu,
&vcpu->arch.guest_tlb[index])) {
kvm_err("%s: handling mapped seg tlb fault failed for %p, index: %u, vcpu: %p, ASID: %#lx\n",
__func__, opc, index, vcpu,
read_c0_entryhi());
kvm_mips_dump_guest_tlbs(vcpu);
local_irq_restore(flags);
return KVM_INVALID_INST;
}
inst = *(opc);
}
local_irq_restore(flags);
} else if (KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG0) {
paddr = kvm_mips_translate_guest_kseg0_to_hpa(vcpu, va);
vaddr = kmap_atomic(pfn_to_page(PHYS_PFN(paddr)));
vaddr += paddr & ~PAGE_MASK;
inst = *(u32 *)vaddr;
kunmap_atomic(vaddr);
} else {
kvm_err("%s: illegal address: %p\n", __func__, opc);
return KVM_INVALID_INST;
}
return inst;
}
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