Hi Christoffer,

On 15/02/18 21:03, Christoffer Dall wrote:
We are about to defer saving and restoring some groups of system
registers to vcpu_put and vcpu_load on supported systems.  This means
that we need some infrastructure to access system registes which

NIT: s/registes/registers/

supports either accessing the memory backing of the register or directly
accessing the system registers, depending on the state of the system
when we access the register.

We do this by defining read/write accessor functions, which can handle
both "immediate" and "deferrable" system registers.  Immediate registers
are always saved/restored in the world-switch path, but deferrable
registers are only saved/restored in vcpu_put/vcpu_load when supported
and sysregs_loaded_on_cpu will be set in that case.

Note that we don't use the deferred mechanism yet in this patch, but only
introduce infrastructure.  This is to improve convenience of review in

NIT: double space after the period.

the subsequent patches where it is clear which registers become
deferred.

Signed-off-by: Christoffer Dall <christoffer.d...@linaro.org>
---

Notes:
     Changes since v3:
      - Changed to a switch-statement based approach to improve
        readability.
Changes since v2:
      - New patch (deferred register handling has been reworked)

  arch/arm64/include/asm/kvm_host.h |  8 ++++++--
  arch/arm64/kvm/sys_regs.c         | 33 +++++++++++++++++++++++++++++++++
  2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h 
b/arch/arm64/include/asm/kvm_host.h
index 68398bf7882f..b463b5e28959 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -284,6 +284,10 @@ struct kvm_vcpu_arch {
/* Virtual SError ESR to restore when HCR_EL2.VSE is set */
        u64 vsesr_el2;
+
+       /* True when deferrable sysregs are loaded on the physical CPU,
+        * see kvm_vcpu_load_sysregs and kvm_vcpu_put_sysregs. */

NIT: I think the preferred style comment is
/*
 * Foo
 */

Cheers,

--
Julien Grall
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