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

[Tom Lendacky]

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@xxxxxxx>
> > ---
> >  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;
> >  		}