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Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and
From: |
Vincent Bernat |
Subject: |
Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge |
Date: |
Mon, 08 Jan 2018 22:51:48 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
❦ 8 janvier 2018 19:16 -0200, Eduardo Habkost <address@hidden> :
> One possible way to work around this problem is to declare that
> QEMU 2.12 with KVM will require Linux v3.6 and newer (because we
> need Linux kernel commit ad756a1603c5 "KVM: VMX: Implement
> PCID/INVPCID for guests with EPT"). I have proposed something
> similar to allow us to enable kvm_pv_eoi by default, some time
> ago:
> https://www.mail-archive.com/address@hidden/msg486559.html
> ("qemu-doc: Document minimum kernel version for KVM in x86_64").
I don't see a way to probe KVM to know what's supported, so yes. Should
I add a paragraph similar to yours or would your patch be merged soon?
What are the consequences of running a too old kernel? Would KVM just
hide PCID flag?
> Second, we need compatibility entries setting pcid=off on
> PC_COMPAT_2_10 so we don't break compatibility on older
> machine-types.
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 6f77eb066587..da5bd8304eb0 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -327,6 +327,14 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
.driver = TYPE_X86_CPU,\
.property = "x-hv-max-vps",\
.value = "0x40",\
+ },{\
+ .driver = "SandyBridge-" TYPE_X86_CPU,\
+ .property = "pcid",\
+ .value = "off",\
+ },{\
+ .driver = "IvyBridge-" TYPE_X86_CPU,\
+ .property = "pcid",\
+ .value = "off",\
},{\
.driver = "i440FX-pcihost",\
.property = "x-pci-hole64-fix",\
I'll resend a proper patch once the first point is cleared.
--
Make sure input cannot violate the limits of the program.
- The Elements of Programming Style (Kernighan & Plauger)