linux-kernel - Re: [PATCH] x86/sev-es: Invalidate the GHCB after completing VMGEXIT

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Date:   Mon, 17 May 2021 10:05:14 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH] x86/sev-es: Invalidate the GHCB after completing VMGEXIT

On 5/17/21 7:33 AM, Joerg Roedel wrote:
> Hi Tom,
> 
> On Fri, May 14, 2021 at 02:12:33PM -0500, Tom Lendacky wrote:
>>  arch/x86/kernel/sev-shared.c |  1 +
>>  arch/x86/kernel/sev.c        | 37 ++++++++++++++++++------------------
>>  2 files changed, 20 insertions(+), 18 deletions(-)
> 
> Having this change in one patch is okay. No need to split it up.
> 
>> +static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
>> +{
>> +	struct sev_es_runtime_data *data;
>> +	struct ghcb *ghcb;
>> +
>> +	data = this_cpu_read(runtime_data);
>> +	ghcb = &data->ghcb_page;
>> +
>> +	if (state->ghcb) {
>> +		/* Restore GHCB from Backup */
>> +		*ghcb = *state->ghcb;
>> +		data->backup_ghcb_active = false;
>> +		state->ghcb = NULL;
>> +	} else {
>> +		vc_ghcb_invalidate(ghcb);
> 
> A comment would be good to explain why the invalidate here is
> necessary.

Ah, good point. I'll add that and send a v2, but I'll wait for further
feedback before sending the next version.

Thanks,
Tom

> 
> Regards,
> 
> 	Joerg
>