3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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From: Wanpeng Li wanpeng.li@hotmail.com
commit d73235d17ba63b53dc0e1051dbc10a1f1be91b71 upstream.
*** Guest State *** CR0: actual=0x0000000000000030, shadow=0x0000000060000010, gh_mask=fffffffffffffff7 CR4: actual=0x0000000000002050, shadow=0x0000000000000000, gh_mask=ffffffffffffe871 CR3 = 0x00000000fffbc000 RSP = 0x0000000000000000 RIP = 0x0000000000000000 RFLAGS=0x00000000 DR7 = 0x0000000000000400 ^^^^^^^^^^
The failed vmentry is triggered by the following testcase when ept=Y:
#include <unistd.h> #include <sys/syscall.h> #include <string.h> #include <stdint.h> #include <linux/kvm.h> #include <fcntl.h> #include <sys/ioctl.h>
long r[5]; int main() { r[2] = open("/dev/kvm", O_RDONLY); r[3] = ioctl(r[2], KVM_CREATE_VM, 0); r[4] = ioctl(r[3], KVM_CREATE_VCPU, 7); struct kvm_regs regs = { .rflags = 0, }; ioctl(r[4], KVM_SET_REGS, ®s); ioctl(r[4], KVM_RUN, 0); }
X86 RFLAGS bit 1 is fixed set, userspace can simply clearing bit 1 of RFLAGS with KVM_SET_REGS ioctl which results in vmentry fails. This patch fixes it by oring X86_EFLAGS_FIXED during ioctl.
Suggested-by: Jim Mattson jmattson@google.com Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Quan Xu quan.xu0@gmail.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Cc: Jim Mattson jmattson@google.com Signed-off-by: Wanpeng Li wanpeng.li@hotmail.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/x86/kvm/x86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6471,7 +6471,7 @@ int kvm_arch_vcpu_ioctl_set_regs(struct #endif
kvm_rip_write(vcpu, regs->rip); - kvm_set_rflags(vcpu, regs->rflags); + kvm_set_rflags(vcpu, regs->rflags | X86_EFLAGS_FIXED);
vcpu->arch.exception.pending = false;