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[Qemu-devel] [PATCH 1/3] kvm: check KVM_CAP_SYNC_MMU with kvm_vm_check_e


From: Greg Kurz
Subject: [Qemu-devel] [PATCH 1/3] kvm: check KVM_CAP_SYNC_MMU with kvm_vm_check_extension()
Date: Thu, 14 Sep 2017 21:25:22 +0200
User-agent: StGit/0.17.1-46-g6855-dirty

On a server-class ppc host, this capability depends on the KVM type,
ie, HV or PR. If both KVM are present in the kernel, we will always
get the HV specific value, even if we explicitely requested PR on
the command line.

This can have an impact if we're using hugepages or a balloon device.

Since we've already created the VM at the time any user calls
kvm_has_sync_mmu(), switching to kvm_vm_check_extension() is
enough to fix any potential issue.

It is okay for the other archs that also implement KVM_CAP_SYNC_MMU,
ie, mips, s390, x86 and arm, because they don't depend on the VM being
created or not.

Signed-off-by: Greg Kurz <address@hidden>
---
 accel/kvm/kvm-all.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f85553a85194..323c567cfb68 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2234,7 +2234,7 @@ int kvm_device_access(int fd, int group, uint64_t attr,
 /* Return 1 on success, 0 on failure */
 int kvm_has_sync_mmu(void)
 {
-    return kvm_check_extension(kvm_state, KVM_CAP_SYNC_MMU);
+    return kvm_vm_check_extension(kvm_state, KVM_CAP_SYNC_MMU);
 }
 
 int kvm_has_vcpu_events(void)




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