From: Paolo Montesel <1809144@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [Bug 1809144] [NEW] SVM instructions fail with SVME bit enabled
Date: Wed, 19 Dec 2018 17:31:26 -0000 [thread overview]
Message-ID: <154524068665.20249.14759163527388138129.malonedeb@wampee.canonical.com> (raw)
Public bug reported:
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
** Affects: qemu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1809144
Title:
SVM instructions fail with SVME bit enabled
Status in QEMU:
New
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
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1809144/+subscriptions
next reply other threads:[~2018-12-19 17:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 17:31 Paolo Montesel [this message]
2018-12-19 18:14 ` [Qemu-devel] [Bug 1809144] [NEW] SVM instructions fail with SVME bit enabled Richard Henderson
2021-04-20 7:57 ` [Bug 1809144] " Thomas Huth
2021-06-20 4:17 ` Launchpad Bug Tracker
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