Commit 6cb1f60b authored by Sean Christopherson's avatar Sean Christopherson Committed by Yu Zhang
Browse files

KVM: x86/mmu: Don't WARN on a NULL shadow page in TDP MMU check 

mainline inclusion
from mainline-v5.14-rc1
commit 6c6e166b
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I7S3VQ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6c6e166b2c8513721d166c74060d26d3f4aecb48



----------------------------------------------------------------------

Treat a NULL shadow page in the "is a TDP MMU" check as valid, non-TDP
root.  KVM uses a "direct" PAE paging MMU when TDP is disabled and the
guest is running with paging disabled.  In that case, root_hpa points at
the pae_root page (of which only 32 bytes are used), not a standard
shadow page, and the WARN fires (a lot).

Fixes: 0b873fd7 ("KVM: x86/mmu: Remove redundant is_tdp_mmu_enabled check")
Cc: David Matlack <dmatlack@google.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210622072454.3449146-1-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarYu Zhang <yu.c.zhang@linux.intel.com>
parent b2e288d7

arch/x86/kvm/mmu/tdp_mmu.h

+6 −4
Original line number Diff line number Diff line
@@ -89,11 +89,13 @@ static inline bool is_tdp_mmu(struct kvm_mmu *mmu) 
	if (WARN_ON(!VALID_PAGE(hpa)))

		return false;



	/*

	 * A NULL shadow page is legal when shadowing a non-paging guest with

	 * PAE paging, as the MMU will be direct with root_hpa pointing at the

	 * pae_root page, not a shadow page.

	 */

	sp = to_shadow_page(hpa);

	if (WARN_ON(!sp))

		return false;



	return is_tdp_mmu_page(sp) && sp->root_count;

	return sp && is_tdp_mmu_page(sp) && sp->root_count;

}

#else

static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; }