Commit 51ee7d6e authored by Tom Lendacky's avatar Tom Lendacky Committed by Borislav Petkov
Browse files

x86/sev-es: Handle MMIO events 



Add a handler for #VC exceptions caused by MMIO intercepts. These
intercepts come along as nested page faults on pages with reserved
bits set.

Signed-off-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: Adapt to VC handling framework ]
Co-developed-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-50-joro@8bytes.org
parent 5e3427a7

arch/x86/include/uapi/asm/svm.h

+5 −0
Original line number Diff line number Diff line
@@ -81,6 +81,11 @@ 
#define SVM_EXIT_AVIC_INCOMPLETE_IPI		0x401

#define SVM_EXIT_AVIC_UNACCELERATED_ACCESS	0x402



/* SEV-ES software-defined VMGEXIT events */

#define SVM_VMGEXIT_MMIO_READ			0x80000001

#define SVM_VMGEXIT_MMIO_WRITE			0x80000002

#define SVM_VMGEXIT_UNSUPPORTED_EVENT		0x8000ffff



#define SVM_EXIT_ERR           -1



#define SVM_EXIT_REASONS \

arch/x86/kernel/sev-es.c

+222 −0
Original line number Diff line number Diff line
@@ -359,6 +359,37 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt, 
	return ES_EXCEPTION;

}



static bool vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,

				 unsigned long vaddr, phys_addr_t *paddr)

{

	unsigned long va = (unsigned long)vaddr;

	unsigned int level;

	phys_addr_t pa;

	pgd_t *pgd;

	pte_t *pte;



	pgd = __va(read_cr3_pa());

	pgd = &pgd[pgd_index(va)];

	pte = lookup_address_in_pgd(pgd, va, &level);

	if (!pte) {

		ctxt->fi.vector     = X86_TRAP_PF;

		ctxt->fi.cr2        = vaddr;

		ctxt->fi.error_code = 0;



		if (user_mode(ctxt->regs))

			ctxt->fi.error_code |= X86_PF_USER;



		return false;

	}



	pa = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;

	pa |= va & ~page_level_mask(level);



	*paddr = pa;



	return true;

}



/* Include code shared with pre-decompression boot stage */

#include "sev-es-shared.c"
@@ -447,6 +478,194 @@ static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt) 
	do_early_exception(ctxt->regs, trapnr);

}



static long *vc_insn_get_reg(struct es_em_ctxt *ctxt)

{

	long *reg_array;

	int offset;



	reg_array = (long *)ctxt->regs;

	offset    = insn_get_modrm_reg_off(&ctxt->insn, ctxt->regs);



	if (offset < 0)

		return NULL;



	offset /= sizeof(long);



	return reg_array + offset;

}



static enum es_result vc_do_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt,

				 unsigned int bytes, bool read)

{

	u64 exit_code, exit_info_1, exit_info_2;

	unsigned long ghcb_pa = __pa(ghcb);

	phys_addr_t paddr;

	void __user *ref;



	ref = insn_get_addr_ref(&ctxt->insn, ctxt->regs);

	if (ref == (void __user *)-1L)

		return ES_UNSUPPORTED;



	exit_code = read ? SVM_VMGEXIT_MMIO_READ : SVM_VMGEXIT_MMIO_WRITE;



	if (!vc_slow_virt_to_phys(ghcb, ctxt, (unsigned long)ref, &paddr)) {

		if (!read)

			ctxt->fi.error_code |= X86_PF_WRITE;



		return ES_EXCEPTION;

	}



	exit_info_1 = paddr;

	/* Can never be greater than 8 */

	exit_info_2 = bytes;



	ghcb->save.sw_scratch = ghcb_pa + offsetof(struct ghcb, shared_buffer);



	return sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, exit_info_1, exit_info_2);

}



static enum es_result vc_handle_mmio_twobyte_ops(struct ghcb *ghcb,

						 struct es_em_ctxt *ctxt)

{

	struct insn *insn = &ctxt->insn;

	unsigned int bytes = 0;

	enum es_result ret;

	int sign_byte;

	long *reg_data;



	switch (insn->opcode.bytes[1]) {

		/* MMIO Read w/ zero-extension */

	case 0xb6:

		bytes = 1;

		fallthrough;

	case 0xb7:

		if (!bytes)

			bytes = 2;



		ret = vc_do_mmio(ghcb, ctxt, bytes, true);

		if (ret)

			break;



		/* Zero extend based on operand size */

		reg_data = vc_insn_get_reg(ctxt);

		if (!reg_data)

			return ES_DECODE_FAILED;



		memset(reg_data, 0, insn->opnd_bytes);



		memcpy(reg_data, ghcb->shared_buffer, bytes);

		break;



		/* MMIO Read w/ sign-extension */

	case 0xbe:

		bytes = 1;

		fallthrough;

	case 0xbf:

		if (!bytes)

			bytes = 2;



		ret = vc_do_mmio(ghcb, ctxt, bytes, true);

		if (ret)

			break;



		/* Sign extend based on operand size */

		reg_data = vc_insn_get_reg(ctxt);

		if (!reg_data)

			return ES_DECODE_FAILED;



		if (bytes == 1) {

			u8 *val = (u8 *)ghcb->shared_buffer;



			sign_byte = (*val & 0x80) ? 0xff : 0x00;

		} else {

			u16 *val = (u16 *)ghcb->shared_buffer;



			sign_byte = (*val & 0x8000) ? 0xff : 0x00;

		}

		memset(reg_data, sign_byte, insn->opnd_bytes);



		memcpy(reg_data, ghcb->shared_buffer, bytes);

		break;



	default:

		ret = ES_UNSUPPORTED;

	}



	return ret;

}



static enum es_result vc_handle_mmio(struct ghcb *ghcb,

				     struct es_em_ctxt *ctxt)

{

	struct insn *insn = &ctxt->insn;

	unsigned int bytes = 0;

	enum es_result ret;

	long *reg_data;



	switch (insn->opcode.bytes[0]) {

	/* MMIO Write */

	case 0x88:

		bytes = 1;

		fallthrough;

	case 0x89:

		if (!bytes)

			bytes = insn->opnd_bytes;



		reg_data = vc_insn_get_reg(ctxt);

		if (!reg_data)

			return ES_DECODE_FAILED;



		memcpy(ghcb->shared_buffer, reg_data, bytes);



		ret = vc_do_mmio(ghcb, ctxt, bytes, false);

		break;



	case 0xc6:

		bytes = 1;

		fallthrough;

	case 0xc7:

		if (!bytes)

			bytes = insn->opnd_bytes;



		memcpy(ghcb->shared_buffer, insn->immediate1.bytes, bytes);



		ret = vc_do_mmio(ghcb, ctxt, bytes, false);

		break;



		/* MMIO Read */

	case 0x8a:

		bytes = 1;

		fallthrough;

	case 0x8b:

		if (!bytes)

			bytes = insn->opnd_bytes;



		ret = vc_do_mmio(ghcb, ctxt, bytes, true);

		if (ret)

			break;



		reg_data = vc_insn_get_reg(ctxt);

		if (!reg_data)

			return ES_DECODE_FAILED;



		/* Zero-extend for 32-bit operation */

		if (bytes == 4)

			*reg_data = 0;



		memcpy(reg_data, ghcb->shared_buffer, bytes);

		break;



		/* Two-Byte Opcodes */

	case 0x0f:

		ret = vc_handle_mmio_twobyte_ops(ghcb, ctxt);

		break;

	default:

		ret = ES_UNSUPPORTED;

	}



	return ret;

}



static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,

					 struct ghcb *ghcb,

					 unsigned long exit_code)
@@ -460,6 +679,9 @@ static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt, 
	case SVM_EXIT_IOIO:

		result = vc_handle_ioio(ghcb, ctxt);

		break;

	case SVM_EXIT_NPF:

		result = vc_handle_mmio(ghcb, ctxt);

		break;

	default:

		/*

		 * Unexpected #VC exception