Re: [PATCH 23/70] x86/sev-es: Add support for handling IOIO exceptions

[David Rientjes <rientjes@google.com>]

On Thu, 19 Mar 2020, Joerg Roedel wrote:

> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> Add support for decoding and handling #VC exceptions for IOIO events.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> [ jroedel@suse.de: Adapted code 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 |  32 +++++
>  arch/x86/kernel/sev-es-shared.c   | 202 ++++++++++++++++++++++++++++++
>  2 files changed, 234 insertions(+)
> 
> diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
> index 193c970a3379..ae5fbd371fd9 100644
> --- a/arch/x86/boot/compressed/sev-es.c
> +++ b/arch/x86/boot/compressed/sev-es.c
> @@ -18,6 +18,35 @@
>  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_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;
> @@ -117,6 +146,9 @@ void boot_vc_handler(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;
> diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
> index f0947ea3c601..46fc5318d1d7 100644
> --- a/arch/x86/kernel/sev-es-shared.c
> +++ b/arch/x86/kernel/sev-es-shared.c
> @@ -205,3 +205,205 @@ 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 |= insn->immediate.value << 16;
> +		break;
> +
> +	/* OUT immediate opcodes */
> +	case 0xe6:
> +	case 0xe7:
> +		*exitinfo |= IOIO_TYPE_OUT;
> +		*exitinfo |= 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_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) {
> +		int df = (regs->flags & X86_EFLAGS_DF) ? -1 : 1;
> +		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 an 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);
> +
> +		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);

The last argument to vc_insn_string_read() is "bool backwards" which in 
this case it appears will always be true?

> +			if (ret)
> +				return ret;
> +		}
> +
> +		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;
> +
> +		/* Everything went well, write back results */
> +		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 {
> +		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_is_valid_rax(ghcb))
> +				return ES_VMM_ERROR;
> +			regs->ax = lower_bits(ghcb->save.rax, bits);
> +		}
> +	}
> +
> +	return ret;
> +}
> -- 
> 2.17.1
> 
>