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x86/sev-es: Add support for handling IOIO exceptions
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Add support for decoding and handling #VC exceptions for IOIO events.

[ jroedel@suse.de: Adapted code to #VC handling framework ]
Co-developed-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-26-joro@8bytes.org
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Tom Lendacky authored and Borislav Petkov committed Sep 7, 2020
1 parent 69add17 commit 25189d0
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32 changes: 32 additions & 0 deletions arch/x86/boot/compressed/sev-es.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,35 @@
struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
struct ghcb *boot_ghcb;

/*
* Copy a version of this function here - insn-eval.c can't be used in
* pre-decompression code.
*/
static bool insn_has_rep_prefix(struct insn *insn)
{
int i;

insn_get_prefixes(insn);

for (i = 0; i < insn->prefixes.nbytes; i++) {
insn_byte_t p = insn->prefixes.bytes[i];

if (p == 0xf2 || p == 0xf3)
return true;
}

return false;
}

/*
* Only a dummy for insn_get_seg_base() - Early boot-code is 64bit only and
* doesn't use segments.
*/
static unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
{
return 0UL;
}

static inline u64 sev_es_rd_ghcb_msr(void)
{
unsigned long low, high;
Expand Down Expand Up @@ -151,6 +180,9 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
goto finish;

switch (exit_code) {
case SVM_EXIT_IOIO:
result = vc_handle_ioio(boot_ghcb, &ctxt);
break;
default:
result = ES_UNSUPPORTED;
break;
Expand Down
214 changes: 214 additions & 0 deletions arch/x86/kernel/sev-es-shared.c
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Original file line number Diff line number Diff line change
Expand Up @@ -218,3 +218,217 @@ static enum es_result vc_insn_string_write(struct es_em_ctxt *ctxt,

return ret;
}

#define IOIO_TYPE_STR BIT(2)
#define IOIO_TYPE_IN 1
#define IOIO_TYPE_INS (IOIO_TYPE_IN | IOIO_TYPE_STR)
#define IOIO_TYPE_OUT 0
#define IOIO_TYPE_OUTS (IOIO_TYPE_OUT | IOIO_TYPE_STR)

#define IOIO_REP BIT(3)

#define IOIO_ADDR_64 BIT(9)
#define IOIO_ADDR_32 BIT(8)
#define IOIO_ADDR_16 BIT(7)

#define IOIO_DATA_32 BIT(6)
#define IOIO_DATA_16 BIT(5)
#define IOIO_DATA_8 BIT(4)

#define IOIO_SEG_ES (0 << 10)
#define IOIO_SEG_DS (3 << 10)

static enum es_result vc_ioio_exitinfo(struct es_em_ctxt *ctxt, u64 *exitinfo)
{
struct insn *insn = &ctxt->insn;
*exitinfo = 0;

switch (insn->opcode.bytes[0]) {
/* INS opcodes */
case 0x6c:
case 0x6d:
*exitinfo |= IOIO_TYPE_INS;
*exitinfo |= IOIO_SEG_ES;
*exitinfo |= (ctxt->regs->dx & 0xffff) << 16;
break;

/* OUTS opcodes */
case 0x6e:
case 0x6f:
*exitinfo |= IOIO_TYPE_OUTS;
*exitinfo |= IOIO_SEG_DS;
*exitinfo |= (ctxt->regs->dx & 0xffff) << 16;
break;

/* IN immediate opcodes */
case 0xe4:
case 0xe5:
*exitinfo |= IOIO_TYPE_IN;
*exitinfo |= (u64)insn->immediate.value << 16;
break;

/* OUT immediate opcodes */
case 0xe6:
case 0xe7:
*exitinfo |= IOIO_TYPE_OUT;
*exitinfo |= (u64)insn->immediate.value << 16;
break;

/* IN register opcodes */
case 0xec:
case 0xed:
*exitinfo |= IOIO_TYPE_IN;
*exitinfo |= (ctxt->regs->dx & 0xffff) << 16;
break;

/* OUT register opcodes */
case 0xee:
case 0xef:
*exitinfo |= IOIO_TYPE_OUT;
*exitinfo |= (ctxt->regs->dx & 0xffff) << 16;
break;

default:
return ES_DECODE_FAILED;
}

switch (insn->opcode.bytes[0]) {
case 0x6c:
case 0x6e:
case 0xe4:
case 0xe6:
case 0xec:
case 0xee:
/* Single byte opcodes */
*exitinfo |= IOIO_DATA_8;
break;
default:
/* Length determined by instruction parsing */
*exitinfo |= (insn->opnd_bytes == 2) ? IOIO_DATA_16
: IOIO_DATA_32;
}
switch (insn->addr_bytes) {
case 2:
*exitinfo |= IOIO_ADDR_16;
break;
case 4:
*exitinfo |= IOIO_ADDR_32;
break;
case 8:
*exitinfo |= IOIO_ADDR_64;
break;
}

if (insn_has_rep_prefix(insn))
*exitinfo |= IOIO_REP;

return ES_OK;
}

static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
struct pt_regs *regs = ctxt->regs;
u64 exit_info_1, exit_info_2;
enum es_result ret;

ret = vc_ioio_exitinfo(ctxt, &exit_info_1);
if (ret != ES_OK)
return ret;

if (exit_info_1 & IOIO_TYPE_STR) {

/* (REP) INS/OUTS */

bool df = ((regs->flags & X86_EFLAGS_DF) == X86_EFLAGS_DF);
unsigned int io_bytes, exit_bytes;
unsigned int ghcb_count, op_count;
unsigned long es_base;
u64 sw_scratch;

/*
* For the string variants with rep prefix the amount of in/out
* operations per #VC exception is limited so that the kernel
* has a chance to take interrupts and re-schedule while the
* instruction is emulated.
*/
io_bytes = (exit_info_1 >> 4) & 0x7;
ghcb_count = sizeof(ghcb->shared_buffer) / io_bytes;

op_count = (exit_info_1 & IOIO_REP) ? regs->cx : 1;
exit_info_2 = min(op_count, ghcb_count);
exit_bytes = exit_info_2 * io_bytes;

es_base = insn_get_seg_base(ctxt->regs, INAT_SEG_REG_ES);

/* Read bytes of OUTS into the shared buffer */
if (!(exit_info_1 & IOIO_TYPE_IN)) {
ret = vc_insn_string_read(ctxt,
(void *)(es_base + regs->si),
ghcb->shared_buffer, io_bytes,
exit_info_2, df);
if (ret)
return ret;
}

/*
* Issue an VMGEXIT to the HV to consume the bytes from the
* shared buffer or to have it write them into the shared buffer
* depending on the instruction: OUTS or INS.
*/
sw_scratch = __pa(ghcb) + offsetof(struct ghcb, shared_buffer);
ghcb_set_sw_scratch(ghcb, sw_scratch);
ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_IOIO,
exit_info_1, exit_info_2);
if (ret != ES_OK)
return ret;

/* Read bytes from shared buffer into the guest's destination. */
if (exit_info_1 & IOIO_TYPE_IN) {
ret = vc_insn_string_write(ctxt,
(void *)(es_base + regs->di),
ghcb->shared_buffer, io_bytes,
exit_info_2, df);
if (ret)
return ret;

if (df)
regs->di -= exit_bytes;
else
regs->di += exit_bytes;
} else {
if (df)
regs->si -= exit_bytes;
else
regs->si += exit_bytes;
}

if (exit_info_1 & IOIO_REP)
regs->cx -= exit_info_2;

ret = regs->cx ? ES_RETRY : ES_OK;

} else {

/* IN/OUT into/from rAX */

int bits = (exit_info_1 & 0x70) >> 1;
u64 rax = 0;

if (!(exit_info_1 & IOIO_TYPE_IN))
rax = lower_bits(regs->ax, bits);

ghcb_set_rax(ghcb, rax);

ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_IOIO, exit_info_1, 0);
if (ret != ES_OK)
return ret;

if (exit_info_1 & IOIO_TYPE_IN) {
if (!ghcb_rax_is_valid(ghcb))
return ES_VMM_ERROR;
regs->ax = lower_bits(ghcb->save.rax, bits);
}
}

return ret;
}

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