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[Bug 1909823] Re: RDPMC check on PCE is backwards
From: |
Bruce Merry |
Subject: |
[Bug 1909823] Re: RDPMC check on PCE is backwards |
Date: |
Sat, 15 May 2021 08:32:34 -0000 |
It looks like this was fixed in c45b426.
** Changed in: qemu
Status: Incomplete => Fix Released
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https://bugs.launchpad.net/bugs/1909823
Title:
RDPMC check on PCE is backwards
Status in QEMU:
Fix Released
Bug description:
At [this
line](https://github.com/qemu/qemu/blob/75ee62ac606bfc9eb59310b9446df3434bf6e8c2/target/i386/tcg/misc_helper.c#L225)
the check on CR4_PCE_MASK is backwards: it's raising an exception if
the flag is set (and CPL != 0) rather than if the flag is clear.
It's low priority at the moment because the instruction isn't
implemented, so you get an illegal opcode exception when expecting a
GPF, or vice versa, but it's a time bomb for if it is ever
implemented.
The Intel docs also indicate that CR0.PE influences the protection; I
don't know if that's already reflected in env->hflags & HF_CPL_MASK.
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