[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH] x86/svm: Reduce vmentry latency

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Mon, 10 Feb 2020 13:09:56 +0100
  • Authentication-results: esa2.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=roger.pau@xxxxxxxxxx; spf=Pass smtp.mailfrom=roger.pau@xxxxxxxxxx; spf=None smtp.helo=postmaster@xxxxxxxxxxxxxxx
  • Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
  • Delivery-date: Mon, 10 Feb 2020 12:10:17 +0000
  • Ironport-sdr: xbTejl4JBp2foj/8YfRCsIs6bv+wFqKN37+DEwsDM//zwwQb23wJqnviw7DHYNSGVvQPPf3fbl KEmoLVU78kodwEYzQdD+TRwOYmJm6aRrCUn9dwj6i1WkGPaq5iQYHZUp642ebTdDeV47yKSKK0 sMGmCPg4zyiA3Qe5Mv8RHf5ULcGyIXSJnz5AVv30Yt//ZdbQrkC9qfQVJDs741SvSnTF7JgKaA TjdARcz2CkFuVL0tE2VTFhUCEKv02OCxgmOn+si2jT+TusQJdvfZsxMvHiflUgzqTie39oUAvo y5w=
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Mon, Feb 10, 2020 at 11:42:06AM +0000, Andrew Cooper wrote:
> Writing to the stack pointer in the middle of a line of pop operations is
> specifically recommended against by the optimisation guide, and is a technique
> used by Speculative Load Hardening to combat SpectreRSB.
> In practice, it causes all further stack-relative accesses to block until the
> write to the stack pointer retires, so the stack engine can get back in sync.
> Pop into any dead register to discard %rax's value without clobbering the
> stack engine.  Smaller compiled code, and runs faster.
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.