On 11/16/18 8:41 AM, Andrew Cooper wrote:
> This is a followup to c/s 96f235c26 which fulfils the remaining TODO item.
>
> First of all, the pre-existing SVM code has a bug. The value in
> msrs->dr_mask[] may be stale, as we allow direct access to these MSRs.
> Resolve this in guest_rdmsr() by reading directly from hardware in the
> affected case.
>
> With the reading/writing logic moved to the common guest_{rd,wr}msr()
> infrastructure, the migration logic can be simplified. The PV migration logic
> drops all of its special casing, and SVM's entire {init,save,load}_msr()
> infrastructure becomes unnecessary.
>
> The resulting diffstat shows quite how expensive the PV special cases where in
> arch_do_domctl().
>
> add/remove: 0/3 grow/shrink: 4/6 up/down: 465/-1494 (-1029)
> Function old new delta
> guest_rdmsr 252 484 +232
> guest_wrmsr 653 822 +169
> msrs_to_send 8 48 +40
> hvm_load_cpu_msrs 489 513 +24
> svm_init_msr 21 - -21
> hvm_save_cpu_msrs 365 343 -22
> read_msr 1089 1001 -88
> write_msr 1829 1689 -140
> svm_msr_read_intercept 1124 970 -154
> svm_load_msr 195 - -195
> svm_save_msr 196 - -196
> svm_msr_write_intercept 1461 1265 -196
> arch_do_domctl 9581 9099 -482
> Total: Before=3314610, After=3313581, chg -0.03%
>
> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
> ---
> CC: Jan Beulich <jbeul...@suse.com>
> CC: Wei Liu <wei.l...@citrix.com>
> CC: Roger Pau Monné <roger....@citrix.com>
> CC: Boris Ostrovsky <boris.ostrov...@oracle.com>
> CC: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>
> CC: Brian Woods <brian.wo...@amd.com>
Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
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