Messages in this thread | | | Date | Fri, 29 Jul 2022 09:25:20 -0500 | Subject | Re: [PATCH v1 1/2] x86/sev: Use per-CPU PSC structure in prep for unaccepted memory support | From | Tom Lendacky <> |
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On 7/29/22 09:18, Dave Hansen wrote: > On 7/29/22 07:01, Tom Lendacky wrote: >> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c >> index c05f0124c410..1f7f6205c4f6 100644 >> --- a/arch/x86/kernel/sev.c >> +++ b/arch/x86/kernel/sev.c >> @@ -104,6 +104,15 @@ struct sev_es_runtime_data { >> * is currently unsupported in SEV-ES guests. >> */ >> unsigned long dr7; >> + >> + /* >> + * Page State Change structure for use when accepting memory or when >> + * changing page state. Interrupts are disabled when using the structure >> + * but an NMI could still be raised, so use a flag to indicate when the >> + * structure is in use and use the MSR protocol in these cases. >> + */ >> + struct snp_psc_desc psc_desc; >> + bool psc_active; >> }; > > This thing: > > struct snp_psc_desc { > struct psc_hdr hdr; > struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY]; > } __packed; > > is 16k, right? Being per-cpu, this might eat up a MB or two of memory > on a big server?
It's just under 2K, 2,032 bytes.
> > Considering that runtime acceptance is already single-threaded[1] *and* > there's a fallback method, why not just have a single copy of this > guarded by a single lock?
This function is called for more than just memory acceptance. It's also called for any changes from or to private or shared, which isn't single-threaded.
Thanks, Tom
> > 1. > https://lore.kernel.org/all/20220614120231.48165-10-kirill.shutemov@linux.intel.com/
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