linux-kernel - Re: [PATCH v4 1/2] x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm

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Message-ID: <52753566-147a-6862-b059-622ec2b7de41@amd.com>
Date: Thu, 26 Sep 2024 12:06:54 -0500
From: "Paluri, PavanKumar" <papaluri@....com>
To: Tom Lendacky <thomas.lendacky@....com>, linux-kernel@...r.kernel.org
Cc: linux-doc@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Eric Van Tassell <Eric.VanTassell@....com>,
 Ashish Kalra <ashish.kalra@....com>, Michael Roth <michael.roth@....com>,
 "H . Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 1/2] x86, KVM:SVM: Move sev specific parsing into
 arch/x86/virt/svm

Hello Tom,

On 9/25/2024 10:57 AM, Tom Lendacky wrote:
> On 9/21/24 22:36, Pavan Kumar Paluri wrote:
>> Move SEV specific kernel command line option parsing support from
>> arch/x86/coco/sev/core.c to arch/x86/virt/svm/cmdline.c so that both
>> host and guest related SEV command line options can be supported.
>>
>> No functional changes intended.
>>
>> Signed-off-by: Pavan Kumar Paluri <papaluri@....com>
>> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>  arch/x86/coco/sev/core.c          | 44 -------------------------------
>>  arch/x86/include/asm/sev-common.h | 29 ++++++++++++++++++++
>>  arch/x86/virt/svm/Makefile        |  1 +
>>  arch/x86/virt/svm/cmdline.c       | 32 ++++++++++++++++++++++
>>  4 files changed, 62 insertions(+), 44 deletions(-)
>>  create mode 100644 arch/x86/virt/svm/cmdline.c
>>
> 

...
>> +extern struct sev_config sev_cfg __read_mostly;
> 
> So I believe the "__read_mostly" attribute really needs to be on the
> actual declaration of the struct, below, in cmdline.c, right?
> 

Yes, I will move this attribute to cmdline.c

> You can check and see which section the sev_cfg struct ends up being
> placed after a build to verify.
>

It is placed in .data.readmostly section.
0000000000000000 g     O .data..read_mostly     0000000000000008 sev_cfg

> Thanks,
> Tom
> 
Thanks for the review,
Pavan

>> +
>>  #endif
>> diff --git a/arch/x86/virt/svm/Makefile b/arch/x86/virt/svm/Makefile
>> index ef2a31bdcc70..eca6d71355fa 100644
>> --- a/arch/x86/virt/svm/Makefile
>> +++ b/arch/x86/virt/svm/Makefile
>> @@ -1,3 +1,4 @@
>>  # SPDX-License-Identifier: GPL-2.0
>>  
>>  obj-$(CONFIG_KVM_AMD_SEV) += sev.o
>> +obj-$(CONFIG_CPU_SUP_AMD) += cmdline.o
>> diff --git a/arch/x86/virt/svm/cmdline.c b/arch/x86/virt/svm/cmdline.c
>> new file mode 100644
>> index 000000000000..964677ab02d6
>> --- /dev/null
>> +++ b/arch/x86/virt/svm/cmdline.c
>> @@ -0,0 +1,32 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * AMD SVM-SEV command line parsing support
>> + *
>> + * Copyright (C) 2023 - 2024 Advanced Micro Devices, Inc.
>> + *
>> + * Author: Michael Roth <michael.roth@....com>
>> + */
>> +
>> +#include <linux/string.h>
>> +#include <linux/printk.h>
>> +
>> +#include <asm/sev-common.h>
>> +
>> +struct sev_config sev_cfg;
>> +
>> +static int __init init_sev_config(char *str)
>> +{
>> +	char *s;
>> +
>> +	while ((s = strsep(&str, ","))) {
>> +		if (!strcmp(s, "debug")) {
>> +			sev_cfg.debug = true;
>> +			continue;
>> +		}
>> +
>> +		pr_info("SEV command-line option '%s' was not recognized\n", s);
>> +	}
>> +
>> +	return 1;
>> +}
>> +__setup("sev=", init_sev_config);