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

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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;
 		}




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