[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 10/16] xen/arm: add Persistent Map (PMAP) infrastructure
On Wed, 8 Jun 2022, Julien Grall wrote: > On 08/06/2022 02:08, Stefano Stabellini wrote: > > > diff --git a/xen/arch/arm/include/asm/pmap.h > > > b/xen/arch/arm/include/asm/pmap.h > > > new file mode 100644 > > > index 000000000000..74398b4c4fe6 > > > --- /dev/null > > > +++ b/xen/arch/arm/include/asm/pmap.h > > > @@ -0,0 +1,32 @@ > > > +#ifndef __ASM_PMAP_H__ > > > +#define __ASM_PMAP_H__ > > > + > > > +#include <xen/mm.h> > > > + > > > +#include <asm/fixmap.h> > > > + > > > +static inline void arch_pmap_map(unsigned int slot, mfn_t mfn) > > > +{ > > > + lpae_t *entry = &xen_fixmap[slot]; > > > + lpae_t pte; > > > + > > > + ASSERT(!lpae_is_valid(*entry)); > > > + > > > + pte = mfn_to_xen_entry(mfn, PAGE_HYPERVISOR_RW); > > > + pte.pt.table = 1; > > > + write_pte(entry, pte); > > > > Here we don't need a tlb flush because we never go from a valid mapping > > to another valid mapping. > > A TLB flush would not be sufficient here. You would need to follow the > break-before-make sequence in order to replace a valid mapping with another > valid mapping. > > > We also go through arch_pmap_unmap which > > clears the mapping and also flushes the tlb. Is that right? > > The PMAP code is using a bitmap to know which entry is used. So when > arch_pmap_map() is called, we also guarantees the entry will be invalid (hence > the ASSERT(!lpae_is_valid()). > > The bit in the bitmap will only be cleared by pmap_unmap() which will result > to a TLB flush. > > > > +} > > > + > > > +static inline void arch_pmap_unmap(unsigned int slot) > > > +{ > > > + lpae_t pte = {}; > > > + > > > + write_pte(&xen_fixmap[slot], pte); > > > + > > > + flush_xen_tlb_range_va_local(FIXMAP_ADDR(slot), PAGE_SIZE); > > > +} > > > + > > > +void arch_pmap_map_slot(unsigned int slot, mfn_t mfn); > > > +void arch_pmap_clear_slot(void *ptr); > > > > What are these two? They are not defined anywhere? > > It is left-over. I will drop them. With those two functions removed, you can add my Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
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