Messages in this thread | | | Date | Wed, 17 Aug 2022 16:17:54 -0500 | Subject | Re: [PATCH v3 1/2] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support | From | Tom Lendacky <> |
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On 8/17/22 11:08, Borislav Petkov wrote: > On Mon, Aug 15, 2022 at 10:57:42AM -0500, Tom Lendacky wrote: >> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c >> index c05f0124c410..40268ce97aad 100644 >> --- a/arch/x86/kernel/sev.c >> +++ b/arch/x86/kernel/sev.c >> @@ -66,6 +66,17 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE); >> */ >> static struct ghcb *boot_ghcb __section(".data"); >> >> +/* >> + * A flag used by set_pages_state() that indicates when the per-CPU GHCB has >> + * been created and registered and thus can be used instead of using the MSR >> + * protocol. The set_pages_state() function eventually invokes vmgexit_psc(), >> + * which only works with a per-CPU GHCB. >> + * >> + * For APs, the per-CPU GHCB is created before they are started and registered >> + * upon startup, so this flag can be used globally for the BSP and APs. >> + */ > > Ok, better, thanks! > >> +static bool ghcb_percpu_ready __section(".data"); > > However, it reads really weird if you have "percpu" in the name of a > variable which is not per CPU... > > Let's just call it "ghcbs_initialized" and be done with it. > > And I still hate the whole thing ofc. > > Do this ontop (and I knew we had a flags thing already): > > (And yes, __read_mostly is in the .data section too).
Cool, will do.
Thanks, Tom
> > --- > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c > index 40268ce97aad..5b3afbf26349 100644 > --- a/arch/x86/kernel/sev.c > +++ b/arch/x86/kernel/sev.c > @@ -66,17 +66,6 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE); > */ > static struct ghcb *boot_ghcb __section(".data"); > > -/* > - * A flag used by set_pages_state() that indicates when the per-CPU GHCB has > - * been created and registered and thus can be used instead of using the MSR > - * protocol. The set_pages_state() function eventually invokes vmgexit_psc(), > - * which only works with a per-CPU GHCB. > - * > - * For APs, the per-CPU GHCB is created before they are started and registered > - * upon startup, so this flag can be used globally for the BSP and APs. > - */ > -static bool ghcb_percpu_ready __section(".data"); > - > /* Bitmap of SEV features supported by the hypervisor */ > static u64 sev_hv_features __ro_after_init; > > @@ -128,7 +117,18 @@ static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa); > > struct sev_config { > __u64 debug : 1, > - __reserved : 63; > + > + /* > + * A flag used by set_pages_state() that indicates when the per-CPU GHCB has > + * been created and registered and thus can be used instead of using the MSR > + * protocol. The set_pages_state() function eventually invokes vmgexit_psc(), > + * which only works with a per-CPU GHCB. > + * > + * For APs, the per-CPU GHCB is created before they are started and registered > + * upon startup, so this flag can be used globally for the BSP and APs. > + */ > + ghcbs_initialized : 1, > + __reserved : 62; > }; > > static struct sev_config sev_cfg __read_mostly; > @@ -762,7 +762,7 @@ static int vmgexit_psc(struct snp_psc_desc *desc) > unsigned long flags; > struct ghcb *ghcb; > > - WARN_ON_ONCE(!ghcb_percpu_ready); > + WARN_ON_ONCE(!sev_cfg.ghcbs_initialized); > > /* > * __sev_get_ghcb() needs to run with IRQs disabled because it is using > @@ -887,7 +887,7 @@ static void set_pages_state(unsigned long vaddr, unsigned int npages, int op) > * Use the MSR protocol when the per-CPU GHCBs are not yet registered, > * since vmgexit_psc() uses the per-CPU GHCB. > */ > - if (!ghcb_percpu_ready) > + if (!sev_cfg.ghcbs_initialized) > return early_set_pages_state(__pa(vaddr), npages, op); > > vaddr = vaddr & PAGE_MASK; > @@ -1268,7 +1268,7 @@ void setup_ghcb(void) > if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) > snp_register_per_cpu_ghcb(); > > - ghcb_percpu_ready = true; > + sev_cfg.ghcbs_initialized = true; > > return; > } >
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