linux-kernel - Re: [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove

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Message-ID: <41bf31aec263780af85037ec3d1397aad24b7218.camel@kernel.org>
Date:   Mon, 13 Sep 2021 23:33:57 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     x86@...nel.org, linux-sgx@...r.kernel.org,
        dave.hansen@...ux.intel.com, yang.zhong@...el.com
Subject: Re: [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove_page

On Mon, 2021-09-13 at 09:11 -0400, Paolo Bonzini wrote:
> Windows expects all pages to be in uninitialized state on startup.
> In order to implement this, we will need a ioctl that performs
> EREMOVE on all pages mapped by a /dev/sgx_vepc file descriptor:
> other possibilities, such as closing and reopening the device,
> are racy.

So what makes it racy, and what do mean by racy in this case?

I.e. you have to do open() and mmap(), and munmap() + close()
for removal. Depending on situation that is racy or not...

And is "Windows" more precisely a "Windows guest running in
Linux QEMU host"? It's ambiguous..

/Jarkko