linux-kernel - Re: [PATCH v3 54/75] x86/sev-es: Handle DR7 read/write events

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Date:   Mon, 25 May 2020 12:59:35 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <jroedel@...e.de>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v3 54/75] x86/sev-es: Handle DR7 read/write events

On Tue, Apr 28, 2020 at 05:17:04PM +0200, Joerg Roedel wrote:
> +static enum es_result vc_handle_dr7_write(struct ghcb *ghcb,
> +					  struct es_em_ctxt *ctxt)
> +{
> +	struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
> +	long val, *reg = vc_insn_get_rm(ctxt);
> +	enum es_result ret;
> +
> +	if (!reg)
> +		return ES_DECODE_FAILED;
> +
> +	val = *reg;
> +
> +	/* Upper 32 bits must be written as zeroes */
> +	if (val >> 32) {
> +		ctxt->fi.vector = X86_TRAP_GP;
> +		ctxt->fi.error_code = 0;
> +		return ES_EXCEPTION;
> +	}
> +
> +	/* Clear out other reservered bits and set bit 10 */

"reserved"

> +	val = (val & 0xffff23ffL) | BIT(10);
> +
> +	/* Early non-zero writes to DR7 are not supported */
> +	if (!data && (val & ~DR7_RESET_VALUE))
> +		return ES_UNSUPPORTED;
> +
> +	/* Using a value of 0 for ExitInfo1 means RAX holds the value */
> +	ghcb_set_rax(ghcb, val);
> +	ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_WRITE_DR7, 0, 0);
> +	if (ret != ES_OK)
> +		return ret;
> +
> +	if (data)
> +		data->dr7 = val;

Are we still returning ES_OK if !data?

> +
> +	return ES_OK;
> +}

-- 
Regards/Gruss,
    Boris.

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