linux-kernel - [PATCH 2/2] KVM: SEV: Fall back to __vmalloc() for SEV-ES scratch area if necessary

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Message-Id: <20211109222350.2266045-3-seanjc@google.com>
Date:   Tue,  9 Nov 2021 22:23:50 +0000
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,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 2/2] KVM: SEV: Fall back to __vmalloc() for SEV-ES scratch
 area if necessary

Use kvzalloc() to allocate KVM's buffer for SEV-ES's GHCB scratch area so
that KVM falls back to __vmalloc() if physically contiguous memory isn't
available.  The buffer is purely a KVM software construct, i.e. there's
no need for it to be physically contiguous, and at a max allowed size of
16kb it's just large enough that kzalloc() could feasibly fail due to
memory fragmentation.

Cc: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index ea8069c9b5cb..2d5a0eea27ea 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2030,7 +2030,7 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
 	__free_page(virt_to_page(svm->vmsa));
 
 	if (svm->ghcb_sa_free)
-		kfree(svm->ghcb_sa);
+		kvfree(svm->ghcb_sa);
 }
 
 static void dump_ghcb(struct vcpu_svm *svm)
@@ -2262,7 +2262,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm)
 			svm->ghcb_sa_sync = false;
 		}
 
-		kfree(svm->ghcb_sa);
+		kvfree(svm->ghcb_sa);
 		svm->ghcb_sa = NULL;
 		svm->ghcb_sa_free = false;
 	}
@@ -2350,7 +2350,7 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
 			       len, GHCB_SCRATCH_AREA_LIMIT);
 			return -EINVAL;
 		}
-		scratch_va = kzalloc(len, GFP_KERNEL_ACCOUNT);
+		scratch_va = kvzalloc(len, GFP_KERNEL_ACCOUNT);
 		if (!scratch_va)
 			return -ENOMEM;
 
@@ -2358,7 +2358,7 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
 			/* Unable to copy scratch area from guest */
 			pr_err("vmgexit: kvm_read_guest for scratch area failed\n");
 
-			kfree(scratch_va);
+			kvfree(scratch_va);
 			return -EFAULT;
 		}
 
-- 
2.34.0.rc0.344.g81b53c2807-goog