From: bluhm <bluhm@openbsd.org>
Date: Tue, 3 Sep 2024 17:19:53 +0000 (+0000)
Subject: For virtual addresses use fixed page frame without AMD SEV reduction.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=be4dcae9074d3088c4d79cb11b24a4018b77fba9;p=openbsd

For virtual addresses use fixed page frame without AMD SEV reduction.

When running as a SEV guest, page frame mask is calculated from the
CPUID provided "physical address bit reduction".  The amd64 pmap
code uses the variable pg_frame instead of the defined PG_FRAME
0x000ffffffffff000.
There was one instance in pmap code where pg_frame was applied to
virtual address, not physical address.  On some machines the address
bit reduction is rather large with six bits.  So the calculated
pg_frame is 0x00003fffffe00000.  However, on amd64 VM_MAX_ADDRESS
is defined as 0x00007fbfdfeff000.  Masking a such large address
with pg_frame caused havoc.  Therefore, when masking virtual
addresses, still use PG_FRAME.

from hshoexer@
---

diff --git a/sys/arch/amd64/amd64/pmap.c b/sys/arch/amd64/amd64/pmap.c
index cf8e59287e4..c7d2dca5e73 100644
--- a/sys/arch/amd64/amd64/pmap.c
+++ b/sys/arch/amd64/amd64/pmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pmap.c,v 1.172 2024/08/29 20:13:42 dv Exp $	*/
+/*	$OpenBSD: pmap.c,v 1.173 2024/09/03 17:19:53 bluhm Exp $	*/
 /*	$NetBSD: pmap.c,v 1.3 2003/05/08 18:13:13 thorpej Exp $	*/
 
 /*
@@ -2159,8 +2159,8 @@ pmap_write_protect(struct pmap *pmap, vaddr_t sva, vaddr_t eva, vm_prot_t prot)
 	shootself = (scr3 == 0);
 
 	/* should be ok, but just in case ... */
-	sva &= pg_frame;
-	eva &= pg_frame;
+	sva &= PG_FRAME;
+	eva &= PG_FRAME;
 
 	if (!(prot & PROT_READ))
 		set |= pg_xo;