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

Tom Lendacky
2017-05-17T20:27:23Z

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@amd.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;
>> }
>