KVM/VMX: Avoid stack engine synchronization uop in __vmx_vcpu_run

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Avoid instructions with explicit uses of the stack pointer between
instructions that implicitly refer to it. The sequence of
POP %reg; ADD $x, %RSP; POP %reg forces emission of synchronization
uop to synchronize the value of the stack pointer in the stack engine
and the out-of-order core.

Using POP with the dummy register instead of ADD $x, %RSP results in a
smaller code size and faster code.

The patch also fixes the reference to the wrong register in the
nearby comment.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Link: https://lore.kernel.org/r/20220816211010.25693-1-ubizjak@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Uros Bizjak 2022-08-16 23:10:10 +02:00 • committed by Paolo Bonzini

parent 5a2a961be2

commit afe30b59d3

1 changed files with 4 additions and 5 deletions

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arch/x86/kvm/vmx/vmenter.S

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