From: Launchpad Bug Tracker <1809144@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1809144] Re: SVM instructions fail with SVME bit enabled
Date: Sun, 20 Jun 2021 04:17:20 -0000 [thread overview]
Message-ID: <162416264113.7948.15262849804962413418.malone@loganberry.canonical.com> (raw)
In-Reply-To: 154524068665.20249.14759163527388138129.malonedeb@wampee.canonical.com
[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
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https://bugs.launchpad.net/bugs/1809144
Title:
SVM instructions fail with SVME bit enabled
Status in QEMU:
Expired
Bug description:
I was trying to use QEMU/TCG to emulate some stuff that uses SVM.
I know SVM is only partially implemented but I gave it a try anyway.
I found that if SVM is enabled in the same basic block in which there's a call to VMSAVE/etc,
the call fails as illegal op because the flags don't get updated correctly.
The pseudocode for the asm I'm running is:
```
EFER |= SVME; set the appropriate bit with wrmsr
vmsave
```
This is an example of the relevant translate.c code:
```
if (!(s->flags & HF_SVME_MASK) || !s->pe) {
goto illegal_op;
}
if (s->cpl != 0) {
gen_exception(s, EXCP0D_GPF, pc_start - s->cs_base);
break;
}
```
s->flags doesn't get updated after the wrmsr instruction and so QEMU
raises an illegal opcode interrupt.
A quick fix is to make the tb end after `wrmsr` instructions, but it's an hack afaik.
I'm not too comfortable with QEMU's code, so I don't know what a proper fix would be.
Cheers,
thebabush
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prev parent reply other threads:[~2021-06-20 4:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 17:31 [Qemu-devel] [Bug 1809144] [NEW] SVM instructions fail with SVME bit enabled Paolo Montesel
2018-12-19 18:14 ` Richard Henderson
2021-04-20 7:57 ` [Bug 1809144] " Thomas Huth
2021-06-20 4:17 ` Launchpad Bug Tracker [this message]
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