linux-kernel - [PATCH 4.9 20/86] KVM: x86: bit 8 of non-leaf PDPEs is not reserved

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Message-Id: <20200720152754.157974606@linuxfoundation.org>
Date:   Mon, 20 Jul 2020 17:36:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nadav Amit <namit@...are.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.9 20/86] KVM: x86: bit 8 of non-leaf PDPEs is not reserved

From: Paolo Bonzini <pbonzini@...hat.com>

commit 5ecad245de2ae23dc4e2dbece92f8ccfbaed2fa7 upstream.

Bit 8 would be the "global" bit, which does not quite make sense for non-leaf
page table entries.  Intel ignores it; AMD ignores it in PDEs and PDPEs, but
reserves it in PML4Es.

Probably, earlier versions of the AMD manual documented it as reserved in PDPEs
as well, and that behavior made it into KVM as well as kvm-unit-tests; fix it.

Cc: stable@...r.kernel.org
Reported-by: Nadav Amit <namit@...are.com>
Fixes: a0c0feb57992 ("KVM: x86: reserve bit 8 of non-leaf PDPEs and PML4Es in 64-bit mode on AMD", 2014-09-03)
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/mmu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3849,7 +3849,7 @@ __reset_rsvds_bits_mask(struct kvm_vcpu
 			nonleaf_bit8_rsvd | rsvd_bits(7, 7) |
 			rsvd_bits(maxphyaddr, 51);
 		rsvd_check->rsvd_bits_mask[0][2] = exb_bit_rsvd |
-			nonleaf_bit8_rsvd | gbpages_bit_rsvd |
+			gbpages_bit_rsvd |
 			rsvd_bits(maxphyaddr, 51);
 		rsvd_check->rsvd_bits_mask[0][1] = exb_bit_rsvd |
 			rsvd_bits(maxphyaddr, 51);