linux-kernel - [PATCH 24/24] KVM: x86/mmu: Dump reserved bits if they're detected on non-MMIO SPTE

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Date:   Thu, 25 Feb 2021 12:47:49 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 24/24] KVM: x86/mmu: Dump reserved bits if they're detected on
 non-MMIO SPTE

Debugging unexpected reserved bit page faults sucks.  Dump the reserved
bits that (likely) caused the page fault to make debugging suck a little
less.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e636fcd529d2..dab0e950a54e 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3555,11 +3555,12 @@ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
 			    __is_rsvd_bits_set(rsvd_check, sptes[level], level);
 
 	if (reserved) {
-		pr_err("%s: detect reserved bits on spte, addr 0x%llx, dump hierarchy:\n",
+		pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n",
 		       __func__, addr);
 		for (level = root; level >= leaf; level--)
-			pr_err("------ spte 0x%llx level %d.\n",
-			       sptes[level], level);
+			pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx",
+			       sptes[level], level,
+			       rsvd_check->rsvd_bits_mask[(sptes[level] >> 7) & 1][level-1]);
 	}
 
 	return reserved;
-- 
2.30.1.766.gb4fecdf3b7-goog