On 08.07.20 16:37, Andrej Utz wrote:
Hi all,
On 02/07/2020 18:26, Ralf Ramsauer wrote:
On 02/07/2020 18:17, Jan Kiszka wrote:
On 02.07.20 18:07, Moritz Walker wrote:
Smells like a regression in that branch for non-root Linux. Is that
562b04e51bb5e2f04bf175383080333237067c63? Can you share you kernel
config?
Yes, its 562b04e51bb5e2f04bf175383080333237067c63. I attached the
kernel config.
I also tried the kernel from jailhouse-images (Linux version 5.4.17)
which leads to the same error
on my AMD-machine:
Ah, AMD! Please see
Yeah, AMD. It isn't always only Intel. :-)
https://groups.google.com/forum/#!msg/jailhouse-dev/1wRKIiGN0GA/_p_NSIBpDwAJ
- in fact a known issue (hardware misbehavior) that we didn't workaround
yet.
Yes, just wanted to mention! Looks familiar.
Ralf, Andrej, any news here.
Andrej?
It's already been a while. Didn't we already have some preliminary
patches for Linux?
As a hacky workaround, you can try:
diff --git a/hypervisor/arch/x86/apic.c b/hypervisor/arch/x86/apic.c
index d36c2033..5160d37d 100644
--- a/hypervisor/arch/x86/apic.c
+++ b/hypervisor/arch/x86/apic.c
@@ -350,7 +350,7 @@ void apic_clear(void)
/* Finally, reset the TPR again and disable the APIC */
apic_ops.write(APIC_REG_TPR, 0);
- apic_ops.write(APIC_REG_SVR, 0xff);
+ //apic_ops.write(APIC_REG_SVR, 0xff);
}
static void apic_send_ipi(unsigned int target_cpu_id, u32 orig_icr_hi,
Or as an alternative apply the following patch to the kernel:
https://groups.google.com/d/msg/jailhouse-dev/1wRKIiGN0GA/P5YeS3oqAQAJ
@Jan: Any ideas how to bring the mentioned patch (or something
equivalent) upstream? I know its a hack and will add proper CPU family
checks, but the linux-x86 folks still may not even touch it. Meanwhile
AMD gains market share and as such more people will try to run non-root
Linux with their CPUs, run into this bug and request support here or
decide to use other hypervisors.
Code-wise, I think you can simply set the mask bit unconditionally right
after enabling if that is the software-expected state and that is just
not available on all CPUs. That code path is not timing sensitive.
But, in order to explain where this comes from and what will happen if
not doing that - at least over Jailhouse -, a verbose commit message and
likely also a code comment will be needed.
Jan
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