| Message ID | 20230619170115.81398-6-julien@xen.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/arm: Add some missing ISBs after updating the PTEs | expand |
Hi Julien, > -----Original Message----- > Subject: [PATCH 5/7] xen/arm: pmap: Add missing ISB in arch_pmap_map() > > From: Julien Grall <jgrall@amazon.com> > > Per the Arm Arm, (Armv7 DDI406C.d A3.8.3 and Armv8 DDI 0487J.a B2.3.12): > > "The DMB and DSB memory barriers affect reads and writes to the memory > system generated by load/store instructions and data or unified cache > maintenance operations being executed by the processor. Instruction > fetches or accesses caused by a hardware translation table access are > not explicit accesses." > > Note that second sentence is not part of the newer Armv8 spec. But the > interpretation is not much different. > > As the entry created by arch_pmap_map() will be used soon after > pmap_map() returns, we want to ensure the DSB in write_pte() has > completed. So add an ISB. > > Fixes: 4f17357b52f6 ("xen/arm: add Persistent Map (PMAP) infrastructure") > Signed-off-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Henry Wang <Henry.Wang@arm.com> I've also tested this patch on top of today's staging by our internal CI, and this patch looks good, so: Tested-by: Henry Wang <Henry.Wang@arm.com> Kind regards, Henry
Hi Julien, > On 19 Jun 2023, at 19:01, Julien Grall <julien@xen.org> wrote: > > From: Julien Grall <jgrall@amazon.com> > > Per the Arm Arm, (Armv7 DDI406C.d A3.8.3 and Armv8 DDI 0487J.a B2.3.12): > > "The DMB and DSB memory barriers affect reads and writes to the memory > system generated by load/store instructions and data or unified cache > maintenance operations being executed by the processor. Instruction > fetches or accesses caused by a hardware translation table access are > not explicit accesses." > > Note that second sentence is not part of the newer Armv8 spec. But the > interpretation is not much different. > > As the entry created by arch_pmap_map() will be used soon after > pmap_map() returns, we want to ensure the DSB in write_pte() has > completed. So add an ISB. > > Fixes: 4f17357b52f6 ("xen/arm: add Persistent Map (PMAP) infrastructure") > Signed-off-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com> Cheers Bertrand > --- > xen/arch/arm/include/asm/pmap.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/xen/arch/arm/include/asm/pmap.h b/xen/arch/arm/include/asm/pmap.h > index e094d13dd282..bca3381796f3 100644 > --- a/xen/arch/arm/include/asm/pmap.h > +++ b/xen/arch/arm/include/asm/pmap.h > @@ -15,6 +15,11 @@ static inline void arch_pmap_map(unsigned int slot, mfn_t mfn) > pte = mfn_to_xen_entry(mfn, PAGE_HYPERVISOR_RW); > pte.pt.table = 1; > write_pte(entry, pte); > + /* > + * The new entry will be used very soon after arch_pmap_map() returns. > + * So ensure the DSB in write_pte() has completed before continuing. > + */ > + isb(); > } > > static inline void arch_pmap_unmap(unsigned int slot) > -- > 2.40.1 >
diff --git a/xen/arch/arm/include/asm/pmap.h b/xen/arch/arm/include/asm/pmap.h index e094d13dd282..bca3381796f3 100644 --- a/xen/arch/arm/include/asm/pmap.h +++ b/xen/arch/arm/include/asm/pmap.h @@ -15,6 +15,11 @@ static inline void arch_pmap_map(unsigned int slot, mfn_t mfn) pte = mfn_to_xen_entry(mfn, PAGE_HYPERVISOR_RW); pte.pt.table = 1; write_pte(entry, pte); + /* + * The new entry will be used very soon after arch_pmap_map() returns. + * So ensure the DSB in write_pte() has completed before continuing. + */ + isb(); } static inline void arch_pmap_unmap(unsigned int slot)