| Message ID | 20240821100215.4119457-2-dmitrii.kuvaiskii@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/sgx: Fix two data races in EAUG/EREMOVE flows | expand |
On Wed Aug 21, 2024 at 1:02 PM EEST, Dmitrii Kuvaiskii wrote: > The page reclaimer thread sets SGX_ENC_PAGE_BEING_RECLAIMED flag when > the enclave page is being reclaimed (moved to the backing store). This > flag however has two logical meanings: > > 1. Don't attempt to load the enclave page (the page is busy), see > __sgx_encl_load_page(). > 2. Don't attempt to remove the PCMD page corresponding to this enclave > page (the PCMD page is busy), see reclaimer_writing_to_pcmd(). > > To reflect these two meanings, split SGX_ENCL_PAGE_BEING_RECLAIMED into > two flags: SGX_ENCL_PAGE_BUSY and SGX_ENCL_PAGE_PCMD_BUSY. Currently, > both flags are set only when the enclave page is being reclaimed (by the > page reclaimer thread). A future commit will introduce new cases when > the enclave page is being operated on; these new cases will set only the > SGX_ENCL_PAGE_BUSY flag. > > Cc: stable@vger.kernel.org > Signed-off-by: Dmitrii Kuvaiskii <dmitrii.kuvaiskii@intel.com> > Reviewed-by: Haitao Huang <haitao.huang@linux.intel.com> > Acked-by: Kai Huang <kai.huang@intel.com> > --- > arch/x86/kernel/cpu/sgx/encl.c | 16 +++++++--------- > arch/x86/kernel/cpu/sgx/encl.h | 10 ++++++++-- > arch/x86/kernel/cpu/sgx/main.c | 4 ++-- > 3 files changed, 17 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c > index 279148e72459..c0a3c00284c8 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -46,10 +46,10 @@ static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_ind > * a check if an enclave page sharing the PCMD page is in the process of being > * reclaimed. > * > - * The reclaimer sets the SGX_ENCL_PAGE_BEING_RECLAIMED flag when it > - * intends to reclaim that enclave page - it means that the PCMD page > - * associated with that enclave page is about to get some data and thus > - * even if the PCMD page is empty, it should not be truncated. > + * The reclaimer sets the SGX_ENCL_PAGE_PCMD_BUSY flag when it intends to > + * reclaim that enclave page - it means that the PCMD page associated with that > + * enclave page is about to get some data and thus even if the PCMD page is > + * empty, it should not be truncated. > * > * Context: Enclave mutex (&sgx_encl->lock) must be held. > * Return: 1 if the reclaimer is about to write to the PCMD page > @@ -77,8 +77,7 @@ static int reclaimer_writing_to_pcmd(struct sgx_encl *encl, > * Stop when reaching the SECS page - it does not > * have a page_array entry and its reclaim is > * started and completed with enclave mutex held so > - * it does not use the SGX_ENCL_PAGE_BEING_RECLAIMED > - * flag. > + * it does not use the SGX_ENCL_PAGE_PCMD_BUSY flag. > */ > if (addr == encl->base + encl->size) > break; > @@ -91,8 +90,7 @@ static int reclaimer_writing_to_pcmd(struct sgx_encl *encl, > * VA page slot ID uses same bit as the flag so it is important > * to ensure that the page is not already in backing store. > */ > - if (entry->epc_page && > - (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)) { > + if (entry->epc_page && (entry->desc & SGX_ENCL_PAGE_PCMD_BUSY)) { > reclaimed = 1; > break; > } > @@ -257,7 +255,7 @@ static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl, > > /* Entry successfully located. */ > if (entry->epc_page) { > - if (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED) > + if (entry->desc & SGX_ENCL_PAGE_BUSY) > return ERR_PTR(-EBUSY); > > return entry; > diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h > index f94ff14c9486..b566b8ad5f33 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.h > +++ b/arch/x86/kernel/cpu/sgx/encl.h > @@ -22,8 +22,14 @@ > /* 'desc' bits holding the offset in the VA (version array) page. */ > #define SGX_ENCL_PAGE_VA_OFFSET_MASK GENMASK_ULL(11, 3) > > -/* 'desc' bit marking that the page is being reclaimed. */ > -#define SGX_ENCL_PAGE_BEING_RECLAIMED BIT(3) > +/* 'desc' bit indicating that the page is busy (being reclaimed). */ > +#define SGX_ENCL_PAGE_BUSY BIT(2) > + > +/* > + * 'desc' bit indicating that PCMD page associated with the enclave page is > + * busy (because the enclave page is being reclaimed). > + */ > +#define SGX_ENCL_PAGE_PCMD_BUSY BIT(3) > > struct sgx_encl_page { > unsigned long desc; > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index 166692f2d501..e94b09c43673 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -204,7 +204,7 @@ static void sgx_encl_ewb(struct sgx_epc_page *epc_page, > void *va_slot; > int ret; > > - encl_page->desc &= ~SGX_ENCL_PAGE_BEING_RECLAIMED; > + encl_page->desc &= ~(SGX_ENCL_PAGE_BUSY | SGX_ENCL_PAGE_PCMD_BUSY); > > va_page = list_first_entry(&encl->va_pages, struct sgx_va_page, > list); > @@ -340,7 +340,7 @@ static void sgx_reclaim_pages(void) > goto skip; > } > > - encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED; > + encl_page->desc |= SGX_ENCL_PAGE_BUSY | SGX_ENCL_PAGE_PCMD_BUSY; > mutex_unlock(&encl_page->encl->lock); > continue; > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> BR, Jarkko
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index 279148e72459..c0a3c00284c8 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -46,10 +46,10 @@ static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_ind * a check if an enclave page sharing the PCMD page is in the process of being * reclaimed. * - * The reclaimer sets the SGX_ENCL_PAGE_BEING_RECLAIMED flag when it - * intends to reclaim that enclave page - it means that the PCMD page - * associated with that enclave page is about to get some data and thus - * even if the PCMD page is empty, it should not be truncated. + * The reclaimer sets the SGX_ENCL_PAGE_PCMD_BUSY flag when it intends to + * reclaim that enclave page - it means that the PCMD page associated with that + * enclave page is about to get some data and thus even if the PCMD page is + * empty, it should not be truncated. * * Context: Enclave mutex (&sgx_encl->lock) must be held. * Return: 1 if the reclaimer is about to write to the PCMD page @@ -77,8 +77,7 @@ static int reclaimer_writing_to_pcmd(struct sgx_encl *encl, * Stop when reaching the SECS page - it does not * have a page_array entry and its reclaim is * started and completed with enclave mutex held so - * it does not use the SGX_ENCL_PAGE_BEING_RECLAIMED - * flag. + * it does not use the SGX_ENCL_PAGE_PCMD_BUSY flag. */ if (addr == encl->base + encl->size) break; @@ -91,8 +90,7 @@ static int reclaimer_writing_to_pcmd(struct sgx_encl *encl, * VA page slot ID uses same bit as the flag so it is important * to ensure that the page is not already in backing store. */ - if (entry->epc_page && - (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)) { + if (entry->epc_page && (entry->desc & SGX_ENCL_PAGE_PCMD_BUSY)) { reclaimed = 1; break; } @@ -257,7 +255,7 @@ static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl, /* Entry successfully located. */ if (entry->epc_page) { - if (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED) + if (entry->desc & SGX_ENCL_PAGE_BUSY) return ERR_PTR(-EBUSY); return entry; diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h index f94ff14c9486..b566b8ad5f33 100644 --- a/arch/x86/kernel/cpu/sgx/encl.h +++ b/arch/x86/kernel/cpu/sgx/encl.h @@ -22,8 +22,14 @@ /* 'desc' bits holding the offset in the VA (version array) page. */ #define SGX_ENCL_PAGE_VA_OFFSET_MASK GENMASK_ULL(11, 3) -/* 'desc' bit marking that the page is being reclaimed. */ -#define SGX_ENCL_PAGE_BEING_RECLAIMED BIT(3) +/* 'desc' bit indicating that the page is busy (being reclaimed). */ +#define SGX_ENCL_PAGE_BUSY BIT(2) + +/* + * 'desc' bit indicating that PCMD page associated with the enclave page is + * busy (because the enclave page is being reclaimed). + */ +#define SGX_ENCL_PAGE_PCMD_BUSY BIT(3) struct sgx_encl_page { unsigned long desc; diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c index 166692f2d501..e94b09c43673 100644 --- a/arch/x86/kernel/cpu/sgx/main.c +++ b/arch/x86/kernel/cpu/sgx/main.c @@ -204,7 +204,7 @@ static void sgx_encl_ewb(struct sgx_epc_page *epc_page, void *va_slot; int ret; - encl_page->desc &= ~SGX_ENCL_PAGE_BEING_RECLAIMED; + encl_page->desc &= ~(SGX_ENCL_PAGE_BUSY | SGX_ENCL_PAGE_PCMD_BUSY); va_page = list_first_entry(&encl->va_pages, struct sgx_va_page, list); @@ -340,7 +340,7 @@ static void sgx_reclaim_pages(void) goto skip; } - encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED; + encl_page->desc |= SGX_ENCL_PAGE_BUSY | SGX_ENCL_PAGE_PCMD_BUSY; mutex_unlock(&encl_page->encl->lock); continue;