From a7cfa7ac1236937dac431845596a39ba27364a00 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Sat, 10 Sep 2016 23:56:46 +0100 Subject: [PATCH] KVM: MIPS: Add fast path TLB refill handler MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org --- arch/mips/include/asm/kvm_host.h | 1 + arch/mips/kvm/entry.c | 78 ++++++++++++++++++++++++++++++++ arch/mips/kvm/mips.c | 8 ++-- 3 files changed, 84 insertions(+), 3 deletions(-) diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index fea538fc5331..80928ffa0150 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -554,6 +554,7 @@ extern int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu); /* Building of entry/exception code */ int kvm_mips_entry_setup(void); void *kvm_mips_build_vcpu_run(void *addr); +void *kvm_mips_build_tlb_refill_exception(void *addr, void *handler); void *kvm_mips_build_exception(void *addr, void *handler); void *kvm_mips_build_exit(void *addr); diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c index 7424d3d566ff..1ae33e0e675c 100644 --- a/arch/mips/kvm/entry.c +++ b/arch/mips/kvm/entry.c @@ -16,6 +16,7 @@ #include #include #include +#include #include /* Register names */ @@ -122,6 +123,9 @@ int kvm_mips_entry_setup(void) */ 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(); @@ -380,6 +384,80 @@ static void *kvm_mips_build_enter_guest(void *addr) return p; } +/** + * 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. diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 7cf85fa1f658..a687864de428 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -264,7 +264,7 @@ static inline void dump_handler(const char *symbol, void *start, void *end) struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) { int err, size; - void *gebase, *p, *handler; + void *gebase, *p, *handler, *refill_start, *refill_end; int i; struct kvm_vcpu *vcpu = kzalloc(sizeof(struct kvm_vcpu), GFP_KERNEL); @@ -317,8 +317,9 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) /* Build guest exception vectors dynamically in unmapped memory */ handler = gebase + 0x2000; - /* TLB Refill, EXL = 0 */ - kvm_mips_build_exception(gebase, handler); + /* TLB refill */ + refill_start = gebase; + refill_end = kvm_mips_build_tlb_refill_exception(refill_start, handler); /* General Exception Entry point */ kvm_mips_build_exception(gebase + 0x180, handler); @@ -344,6 +345,7 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) pr_debug("#include \n"); pr_debug("\n"); dump_handler("kvm_vcpu_run", vcpu->arch.vcpu_run, p); + dump_handler("kvm_tlb_refill", refill_start, refill_end); dump_handler("kvm_gen_exc", gebase + 0x180, gebase + 0x200); dump_handler("kvm_exit", gebase + 0x2000, vcpu->arch.vcpu_run); -- 2.20.1