KVM: MIPS: Add fast path TLB refill handler
Use functions from the general MIPS TLB exception vector generation code
(tlbex.c) to construct a fast path TLB refill handler similar to the
general one, but cut down and capable of preserving K0 and K1.
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
diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c
index 7424d3d..1ae33e0 100644
--- a/arch/mips/kvm/entry.c
+++ b/arch/mips/kvm/entry.c
@@ -16,6 +16,7 @@
#include <asm/mmu_context.h>
#include <asm/msa.h>
#include <asm/setup.h>
+#include <asm/tlbex.h>
#include <asm/uasm.h>
/* Register names */
@@ -122,6 +123,9 @@
*/
unsigned int kscratch_mask = cpu_data[0].kscratch_mask;
+ if (pgd_reg != -1)
+ kscratch_mask &= ~BIT(pgd_reg);
+
/* Pick a scratch register for storing VCPU */
if (kscratch_mask) {
scratch_vcpu[0] = c0_kscratch();
@@ -381,6 +385,80 @@
}
/**
+ * kvm_mips_build_tlb_refill_exception() - Assemble TLB refill handler.
+ * @addr: Address to start writing code.
+ * @handler: Address of common handler (within range of @addr).
+ *
+ * Assemble TLB refill exception fast path handler for guest execution.
+ *
+ * Returns: Next address after end of written function.
+ */
+void *kvm_mips_build_tlb_refill_exception(void *addr, void *handler)
+{
+ u32 *p = addr;
+ struct uasm_label labels[2];
+ struct uasm_reloc relocs[2];
+ struct uasm_label *l = labels;
+ struct uasm_reloc *r = relocs;
+
+ memset(labels, 0, sizeof(labels));
+ memset(relocs, 0, sizeof(relocs));
+
+ /* Save guest k1 into scratch register */
+ UASM_i_MTC0(&p, K1, scratch_tmp[0], scratch_tmp[1]);
+
+ /* Get the VCPU pointer from the VCPU scratch register */
+ UASM_i_MFC0(&p, K1, scratch_vcpu[0], scratch_vcpu[1]);
+
+ /* Save guest k0 into VCPU structure */
+ UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu, arch.gprs[K0]), K1);
+
+ /*
+ * Some of the common tlbex code uses current_cpu_type(). For KVM we
+ * assume symmetry and just disable preemption to silence the warning.
+ */
+ preempt_disable();
+
+ /*
+ * Now for the actual refill bit. A lot of this can be common with the
+ * Linux TLB refill handler, however we don't need to handle so many
+ * cases. We only need to handle user mode refills, and user mode runs
+ * with 32-bit addressing.
+ *
+ * Therefore the branch to label_vmalloc generated by build_get_pmde64()
+ * that isn't resolved should never actually get taken and is harmless
+ * to leave in place for now.
+ */
+
+#ifdef CONFIG_64BIT
+ build_get_pmde64(&p, &l, &r, K0, K1); /* get pmd in K1 */
+#else
+ build_get_pgde32(&p, K0, K1); /* get pgd in K1 */
+#endif
+
+ /* we don't support huge pages yet */
+
+ build_get_ptep(&p, K0, K1);
+ build_update_entries(&p, K0, K1);
+ build_tlb_write_entry(&p, &l, &r, tlb_random);
+
+ preempt_enable();
+
+ /* Get the VCPU pointer from the VCPU scratch register again */
+ UASM_i_MFC0(&p, K1, scratch_vcpu[0], scratch_vcpu[1]);
+
+ /* Restore the guest's k0/k1 registers */
+ UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu, arch.gprs[K0]), K1);
+ uasm_i_ehb(&p);
+ UASM_i_MFC0(&p, K1, scratch_tmp[0], scratch_tmp[1]);
+
+ /* Jump to guest */
+ uasm_i_eret(&p);
+
+ return p;
+}
+
+/**
* kvm_mips_build_exception() - Assemble first level guest exception handler.
* @addr: Address to start writing code.
* @handler: Address of common handler (within range of @addr).