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

From: Sean Christopherson
Date: Tue Nov 09 2021 - 17:51:46 EST


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@xxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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