Re: MemoryFence()


Andrew Fish <afish@...>
 

On Feb 5, 2021, at 7:38 AM, Paolo Bonzini <pbonzini@...> wrote:

On 05/02/21 16:34, Laszlo Ersek wrote:
And your code is wrong because the*original*, namely the MSFT
implementation of MemoryFence() in edk2, is bugged:
* MdePkg/Library/BaseLib/X86MemoryFence.c:
/**
Used to serialize load and store operations.

All loads and stores that proceed calls to this function are guaranteed to be
globally visible when this function returns.

**/
VOID
EFIAPI
MemoryFence (
VOID
)
{
return;
}
I think it's okay-ish (it works as long as you don't do link-time optimization, but it's less efficient than a compiler intrinsic) because X86MemoryFence.c is a separate file.
We do link time optimization on VC++ and clang.

Thanks,

Andrew Fish

Paolo

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