Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On Fri, 11 Aug 2017 14:07:14 +0200 Peter Zijlstra wrote: > It goes like: > > CPU0CPU1 > > unhook page > cli > traverse page tables > TLB invalidate ---> >

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On Fri, Aug 11, 2017 at 03:07:29PM +0200, Juergen Gross wrote: > On 11/08/17 14:54, Peter Zijlstra wrote: > > On Fri, Aug 11, 2017 at 02:46:41PM +0200, Juergen Gross wrote: > >> Aah, okay. Now I understand the problem. The TLB isn't the issue but the > >> IPI is serving two purposes here: TLB

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On 11/08/17 14:54, Peter Zijlstra wrote: > On Fri, Aug 11, 2017 at 02:46:41PM +0200, Juergen Gross wrote: >> Aah, okay. Now I understand the problem. The TLB isn't the issue but the >> IPI is serving two purposes here: TLB flushing (which is allowed to >> happen at any time) and serialization

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On Fri, Aug 11, 2017 at 02:46:41PM +0200, Juergen Gross wrote: > Aah, okay. Now I understand the problem. The TLB isn't the issue but the > IPI is serving two purposes here: TLB flushing (which is allowed to > happen at any time) and serialization regarding access to critical pages > (which seems

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On 11/08/17 14:35, Peter Zijlstra wrote: > On Fri, Aug 11, 2017 at 02:22:25PM +0200, Juergen Gross wrote: >> Wait - the TLB can be cleared at any time, as Andrew was pointing out. >> No cpu can rely on an address being accessible just because IF is being >> cleared. All that matters is the

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On Fri, Aug 11, 2017 at 02:22:25PM +0200, Juergen Gross wrote: > Wait - the TLB can be cleared at any time, as Andrew was pointing out. > No cpu can rely on an address being accessible just because IF is being > cleared. All that matters is the existing and valid page table entry. > > So clearing

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On 11/08/17 12:56, Peter Zijlstra wrote: > On Fri, Aug 11, 2017 at 11:23:10AM +0200, Vitaly Kuznetsov wrote: >> Peter Zijlstra writes: >> >>> On Thu, Aug 10, 2017 at 07:08:22PM +, Jork Loeser wrote: >>> >> Subject: Re: [tip:x86/platform] x86/hyper-v: Use hypercall

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On Fri, Aug 11, 2017 at 12:05:45PM +0100, Andrew Cooper wrote: > >> Oh, I see your concern. Hyper-V, however, is not the first x86 > >> hypervisor trying to avoid IPIs on remote TLB flush, Xen does this > >> too. Briefly looking at xen_flush_tlb_others() I don't see anything > >> special, do we

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On 11/08/17 11:56, Peter Zijlstra wrote: > On Fri, Aug 11, 2017 at 11:23:10AM +0200, Vitaly Kuznetsov wrote: >> Peter Zijlstra writes: >> >>> On Thu, Aug 10, 2017 at 07:08:22PM +, Jork Loeser wrote: >>> >> Subject: Re: [tip:x86/platform] x86/hyper-v: Use hypercall

Re: [Xen-devel] [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

On Fri, Aug 11, 2017 at 11:23:10AM +0200, Vitaly Kuznetsov wrote: > Peter Zijlstra writes: > > > On Thu, Aug 10, 2017 at 07:08:22PM +, Jork Loeser wrote: > > > >> > > Subject: Re: [tip:x86/platform] x86/hyper-v: Use hypercall for remote > >> > > TLB flush > >> > >> >