Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

❦ 8 janvier 2018 21:19 -0200, Eduardo Habkost  : >> > GET_SUPPORTED_CPUID seems to still return PCID as supported >> > without EPT, doesn't it? >> >> Indeed it is! It will also be useful for KPTI performance without >> INVPCID, but it won't be useful without EPT. > >

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

❦ 8 janvier 2018 20:56 -0200, Eduardo Habkost  : > (BTW, is PCID useful for KPTI performance without INVPCID?) It seems it is: https://mail-archive.com/linux-kernel@vger.kernel.org/msg1576774.html -- Don't use conditional branches as a substitute for a logical

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

❦ 8 janvier 2018 17:37 -0500, Paolo Bonzini  : >> 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

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

On Mon, Jan 08, 2018 at 06:09:30PM -0500, Paolo Bonzini wrote: > > > - Original Message - > > From: "Eduardo Habkost" > > To: "Paolo Bonzini" > > Cc: "Vincent Bernat" , "Richard Henderson" > > ,

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

- Original Message - > From: "Eduardo Habkost" > To: "Paolo Bonzini" > Cc: "Vincent Bernat" , "Richard Henderson" > , qemu-devel@nongnu.org > Sent: Monday, January 8, 2018 11:56:25 PM > Subject: Re: [PATCH]

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

On Mon, Jan 08, 2018 at 05:37:16PM -0500, Paolo Bonzini wrote: > > > - Original Message - > > From: "Eduardo Habkost" > > To: "Vincent Bernat" > > Cc: "Paolo Bonzini" , "Richard Henderson" > > ,

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

- Original Message - > From: "Eduardo Habkost" > To: "Vincent Bernat" > Cc: "Paolo Bonzini" , "Richard Henderson" > , qemu-devel@nongnu.org > Sent: Monday, January 8, 2018 10:16:23 PM > Subject: Re: [PATCH]

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

On Mon, Jan 08, 2018 at 11:22:36PM +0100, Vincent Bernat wrote: > ❦ 8 janvier 2018 20:14 -0200, Eduardo Habkost  : > > >> What are the consequences of running a too old kernel? Would KVM just > >> hide PCID flag? > > > > On an old kernel, the SandyBridge and IvyBridge CPU

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

❦ 8 janvier 2018 20:14 -0200, Eduardo Habkost  : >> What are the consequences of running a too old kernel? Would KVM just >> hide PCID flag? > > On an old kernel, the SandyBridge and IvyBridge CPU models will > be unexpectedly become not runnable. But, isn't it the same

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

On Mon, Jan 08, 2018 at 10:51:48PM +0100, Vincent Bernat wrote: > ❦ 8 janvier 2018 19:16 -0200, Eduardo Habkost  : > > > 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

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

❦ 8 janvier 2018 19:16 -0200, Eduardo Habkost  : > 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

Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

On Mon, Jan 08, 2018 at 09:50:52PM +0100, Vincent Bernat wrote: > PCID has been introduced in Sandy Bridge and, currently, KVM doesn't > object exposing it to VM as long as it is present on the host. Update > CPU model for both Sandy Bridge and Ivy Bridge accordingly. > > Signed-off-by: Vincent