Commit a7cfa7ac authored by James Hogan's avatar James Hogan
Browse files

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: default avatarJames 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
parent 29b500b5

arch/mips/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

arch/mips/kvm/entry.c

+78 −0
Original line number Diff line number Diff line
@@ -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 @@ 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.

arch/mips/kvm/mips.c

+5 −3
Original line number Diff line number Diff line
@@ -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 <asm/regdef.h>\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);

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