linux-kernel - Re: [PATCH v5 18/32] x86, mpparse: Use memremap to map the mpf and mpc data

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Date:   Wed, 17 May 2017 15:26:58 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <kexec@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <iommu@...ts.linux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 18/32] x86, mpparse: Use memremap to map the mpf and
 mpc data

On 5/16/2017 3:36 AM, Borislav Petkov wrote:
> On Tue, Apr 18, 2017 at 04:19:30PM -0500, Tom Lendacky wrote:
>> The SMP MP-table is built by UEFI and placed in memory in a decrypted
>> state. These tables are accessed using a mix of early_memremap(),
>> early_memunmap(), phys_to_virt() and virt_to_phys(). Change all accesses
>> to use early_memremap()/early_memunmap(). This allows for proper setting
>> of the encryption mask so that the data can be successfully accessed when
>> SME is active.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>  arch/x86/kernel/mpparse.c |  102 +++++++++++++++++++++++++++++++--------------
>>  1 file changed, 71 insertions(+), 31 deletions(-)
>>
>> diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
>> index fd37f39..afbda41d 100644
>> --- a/arch/x86/kernel/mpparse.c
>> +++ b/arch/x86/kernel/mpparse.c
>> @@ -429,7 +429,21 @@ static inline void __init construct_default_ISA_mptable(int mpc_default_type)
>>  	}
>>  }
>>
>> -static struct mpf_intel *mpf_found;
>> +static unsigned long mpf_base;
>> +
>> +static void __init unmap_mpf(struct mpf_intel *mpf)
>> +{
>> +	early_memunmap(mpf, sizeof(*mpf));
>> +}
>> +
>> +static struct mpf_intel * __init map_mpf(unsigned long paddr)
>> +{
>> +	struct mpf_intel *mpf;
>> +
>> +	mpf = early_memremap(paddr, sizeof(*mpf));
>> +
>> +	return mpf;
>
> 	return early_memremap(paddr, sizeof(*mpf));
>

Ok.

> ...
>
>> @@ -842,25 +873,26 @@ static int __init update_mp_table(void)
>>  	if (!enable_update_mptable)
>>  		return 0;
>>
>> -	mpf = mpf_found;
>> -	if (!mpf)
>> +	if (!mpf_base)
>>  		return 0;
>>
>> +	mpf = map_mpf(mpf_base);
>> +
>>  	/*
>>  	 * Now see if we need to go further.
>>  	 */
>>  	if (mpf->feature1 != 0)
>
> You're kidding, right? map_mpf() *can* return NULL.

Ugh...  don't know how I forgot about that. Will fix everywhere.

>
> Also, simplify that test:
>
> 	if (mpf->feature1)
> 		...

Ok, I can do that but I hope no one says anything about it being
unrelated to the patch. :)

>
>
>> -		return 0;
>> +		goto do_unmap_mpf;
>>
>>  	if (!mpf->physptr)
>> -		return 0;
>> +		goto do_unmap_mpf;
>>
>> -	mpc = phys_to_virt(mpf->physptr);
>> +	mpc = map_mpc(mpf->physptr);
>
> Again: error checking !!!
>
> You have other calls to early_memremap()/map_mpf() in this patch. Please
> add error checking everywhere.

Yup.

>
>>
>>  	if (!smp_check_mpc(mpc, oem, str))
>> -		return 0;
>> +		goto do_unmap_mpc;
>>
>> -	pr_info("mpf: %llx\n", (u64)virt_to_phys(mpf));
>> +	pr_info("mpf: %llx\n", (u64)mpf_base);
>>  	pr_info("physptr: %x\n", mpf->physptr);
>>
>>  	if (mpc_new_phys && mpc->length > mpc_new_length) {
>> @@ -878,21 +910,23 @@ static int __init update_mp_table(void)
>>  		new = mpf_checksum((unsigned char *)mpc, mpc->length);
>>  		if (old == new) {
>>  			pr_info("mpc is readonly, please try alloc_mptable instead\n");
>> -			return 0;
>> +			goto do_unmap_mpc;
>>  		}
>>  		pr_info("use in-position replacing\n");
>>  	} else {
>>  		mpf->physptr = mpc_new_phys;
>> -		mpc_new = phys_to_virt(mpc_new_phys);
>> +		mpc_new = map_mpc(mpc_new_phys);
>
> Ditto.
>
>>  		memcpy(mpc_new, mpc, mpc->length);
>> +		unmap_mpc(mpc);
>>  		mpc = mpc_new;
>>  		/* check if we can modify that */
>>  		if (mpc_new_phys - mpf->physptr) {
>>  			struct mpf_intel *mpf_new;
>>  			/* steal 16 bytes from [0, 1k) */
>>  			pr_info("mpf new: %x\n", 0x400 - 16);
>> -			mpf_new = phys_to_virt(0x400 - 16);
>> +			mpf_new = map_mpf(0x400 - 16);
>
> Ditto.
>
>>  			memcpy(mpf_new, mpf, 16);
>> +			unmap_mpf(mpf);
>>  			mpf = mpf_new;
>>  			mpf->physptr = mpc_new_phys;
>>  		}
>