linux-kernel - Re: [RFC PATCH V5 05/15] clocksource/drivers/hyper-v: decrypt hyperv tsc page in sev-snp enlightened guest

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Date:   Thu, 4 May 2023 19:54:28 +0300
From:   Zhi Wang <zhi.wang.linux@...il.com>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, seanjc@...gle.com, pbonzini@...hat.com,
        jgross@...e.com, tiala@...rosoft.com, kirill@...temov.name,
        jiangshan.ljs@...group.com, peterz@...radead.org,
        ashish.kalra@....com, srutherford@...gle.com,
        akpm@...ux-foundation.org, anshuman.khandual@....com,
        pawan.kumar.gupta@...ux.intel.com, adrian.hunter@...el.com,
        daniel.sneddon@...ux.intel.com, alexander.shishkin@...ux.intel.com,
        sandipan.das@....com, ray.huang@....com, brijesh.singh@....com,
        michael.roth@....com, thomas.lendacky@....com,
        venu.busireddy@...cle.com, sterritt@...gle.com,
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        pangupta@....com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH V5 05/15] clocksource/drivers/hyper-v: decrypt
 hyperv tsc page in sev-snp enlightened guest

On Mon,  1 May 2023 04:57:15 -0400
Tianyu Lan <ltykernel@...il.com> wrote:

> From: Tianyu Lan <tiala@...rosoft.com>
> 
> Hyper-V tsc page is shared with hypervisor and it should
> be decrypted in sev-snp enlightened guest when it's used.
> 
> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> ---
> Change since RFC V2:
>        * Change the Subject line prefix
> ---
>  drivers/clocksource/hyperv_timer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index bcd9042a0c9f..66e29a19770b 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -376,7 +376,7 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
>  static union {
>  	struct ms_hyperv_tsc_page page;
>  	u8 reserved[PAGE_SIZE];
> -} tsc_pg __aligned(PAGE_SIZE);
> +} tsc_pg __bss_decrypted __aligned(PAGE_SIZE);
>  

Out of curiosity, this is not a on/off for VM with paravisor and full-enlightened VM, how
does change affect the case of VM with paravisor? I assume the VM with paravisor works fine
without this previously.

>  static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page;
>  static unsigned long tsc_pfn;