[PATCH 47/70] x86/sev-es: Handle MMIO events

Joerg Roedel
2020-03-19T09:17:09Z

From: Tom Lendacky <thomas.lendacky@amd.com>

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

TODO:
- Add return values of helper functions
- Check permissions on page-table walks
- Check data segments
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: Adapt to VC handling framework ]
Co-developed-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/boot/compressed/sev-es.c | 5 +
arch/x86/include/uapi/asm/svm.h | 5 +
arch/x86/kernel/sev-es.c | 188 ++++++++++++++++++++++++++++++
3 files changed, 198 insertions(+)

diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
index 40eaf24db641..53c65fc09341 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -100,6 +100,11 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
return ES_OK;
}

+static phys_addr_t vc_slow_virt_to_phys(struct ghcb *ghcb, long vaddr)
+{
+ return (phys_addr_t)vaddr;
+}
+
#undef __init
#undef __pa
#define __init
diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index c68d1618c9b0..8f36ae021a7f 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -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 \
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 6d45a2499460..6b0f82f81229 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -240,6 +240,25 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
return ES_EXCEPTION;
}

+static phys_addr_t vc_slow_virt_to_phys(struct ghcb *ghcb, long vaddr)
+{
+ unsigned long va = (unsigned long)vaddr;
+ unsigned int level;
+ phys_addr_t pa;
+ pgd_t *pgd;
+ pte_t *pte;
+
+ pgd = pgd_offset(current->active_mm, va);
+ pte = lookup_address_in_pgd(pgd, va, &level);
+ if (!pte)
+ return 0;
+
+ pa = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
+ pa |= va & ~page_level_mask(level);
+
+ return pa;
+}
+
/* Include code shared with pre-decompression boot stage */
#include "sev-es-shared.c"

@@ -295,6 +314,172 @@ static void __init vc_early_vc_forward_exception(struct es_em_ctxt *ctxt)
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);
+ 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;
+
+ exit_info_1 = vc_slow_virt_to_phys(ghcb, (long)ref);
+ exit_info_2 = bytes; /* Can never be greater than 8 */
+
+ 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);
+ 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 (bytes == 1) {
+ u8 *val = (u8 *)ghcb->shared_buffer;
+
+ sign_byte = (*val & 0x80) ? 0x00 : 0xff;
+ } else {
+ u16 *val = (u16 *)ghcb->shared_buffer;
+
+ sign_byte = (*val & 0x8000) ? 0x00 : 0xff;
+ }
+ 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);
+ 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 (bytes == 4)
+ *reg_data = 0; /* Zero-extend for 32-bit operation */
+
+ 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)
@@ -308,6 +493,9 @@ 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
--
2.17.1