| Message ID | 20220629035426.20013-5-alex.sierra@amd.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | Add MEMORY_DEVICE_COHERENT for coherent device memory mapping | expand |
On 29.06.22 05:54, Alex Sierra wrote: > This case is used to migrate pages from device memory, back to system > memory. Device coherent type memory is cache coherent from device and CPU > point of view. > > Signed-off-by: Alex Sierra <alex.sierra@amd.com> > Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> > Reviewed-by: Alistair Poppple <apopple@nvidia.com> > Signed-off-by: Christoph Hellwig <hch@lst.de> I'm not too familiar with this code, please excuse my naive questions: > @@ -148,15 +148,21 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > if (is_writable_device_private_entry(entry)) > mpfn |= MIGRATE_PFN_WRITE; > } else { > - if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) > - goto next; Why not exclude MIGRATE_VMA_SELECT_DEVICE_PRIVATE here? IIRC that would have happened before this change. > pfn = pte_pfn(pte); > - if (is_zero_pfn(pfn)) { > + if (is_zero_pfn(pfn) && > + (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { > mpfn = MIGRATE_PFN_MIGRATE; > migrate->cpages++; > goto next; > } > page = vm_normal_page(migrate->vma, addr, pte); > + if (page && !is_zone_device_page(page) && I'm wondering if that check logically belongs into patch #2. > + !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) > + goto next; > + else if (page && is_device_coherent_page(page) && > + (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) || > + page->pgmap->owner != migrate->pgmap_owner)) In general LGTM
David Hildenbrand <david@redhat.com> writes: > On 29.06.22 05:54, Alex Sierra wrote: >> This case is used to migrate pages from device memory, back to system >> memory. Device coherent type memory is cache coherent from device and CPU >> point of view. >> >> Signed-off-by: Alex Sierra <alex.sierra@amd.com> >> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> >> Reviewed-by: Alistair Poppple <apopple@nvidia.com> >> Signed-off-by: Christoph Hellwig <hch@lst.de> > > > I'm not too familiar with this code, please excuse my naive questions: > >> @@ -148,15 +148,21 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, >> if (is_writable_device_private_entry(entry)) >> mpfn |= MIGRATE_PFN_WRITE; >> } else { >> - if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) >> - goto next; > > Why not exclude MIGRATE_VMA_SELECT_DEVICE_PRIVATE here? IIRC that would > have happened before this change. I might be missing something as I don't quite follow - this path is for normal system pages so we only want to skip selecting them if MIGRATE_VMA_SELECT_SYSTEM or MIGRATE_VMA_SELECT_DEVICE_COHERENT aren't set. Note that MIGRATE_VMA_SELECT_DEVICE_PRIVATE doesn't apply here because we already know it's not a device private page by virtue of pte_present(pte) == True. >> pfn = pte_pfn(pte); >> - if (is_zero_pfn(pfn)) { >> + if (is_zero_pfn(pfn) && >> + (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { >> mpfn = MIGRATE_PFN_MIGRATE; >> migrate->cpages++; >> goto next; >> } >> page = vm_normal_page(migrate->vma, addr, pte); >> + if (page && !is_zone_device_page(page) && > > I'm wondering if that check logically belongs into patch #2. I don't think so as it would break functionality until the below conditionals are added - we explicitly don't want to skip is_zone_device_page(page) == False here because that is the pages we are trying to select. You could add in this: >> + !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) But then in patch 2 we know this can never be true because we've already checked for !MIGRATE_VMA_SELECT_SYSTEM there. >> + goto next; >> + else if (page && is_device_coherent_page(page) && >> + (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) || >> + page->pgmap->owner != migrate->pgmap_owner)) > > > In general LGTM
On 30.06.22 13:44, Alistair Popple wrote: > > David Hildenbrand <david@redhat.com> writes: > >> On 29.06.22 05:54, Alex Sierra wrote: >>> This case is used to migrate pages from device memory, back to system >>> memory. Device coherent type memory is cache coherent from device and CPU >>> point of view. >>> >>> Signed-off-by: Alex Sierra <alex.sierra@amd.com> >>> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> >>> Reviewed-by: Alistair Poppple <apopple@nvidia.com> >>> Signed-off-by: Christoph Hellwig <hch@lst.de> >> >> >> I'm not too familiar with this code, please excuse my naive questions: >> >>> @@ -148,15 +148,21 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, >>> if (is_writable_device_private_entry(entry)) >>> mpfn |= MIGRATE_PFN_WRITE; >>> } else { >>> - if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) >>> - goto next; >> >> Why not exclude MIGRATE_VMA_SELECT_DEVICE_PRIVATE here? IIRC that would >> have happened before this change. > > I might be missing something as I don't quite follow - this path is for > normal system pages so we only want to skip selecting them if > MIGRATE_VMA_SELECT_SYSTEM or MIGRATE_VMA_SELECT_DEVICE_COHERENT aren't > set. > > Note that MIGRATE_VMA_SELECT_DEVICE_PRIVATE doesn't apply here because > we already know it's not a device private page by virtue of > pte_present(pte) == True. Ah, stupid me, pte_present(pte) is the key. > >>> pfn = pte_pfn(pte); >>> - if (is_zero_pfn(pfn)) { >>> + if (is_zero_pfn(pfn) && >>> + (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { >>> mpfn = MIGRATE_PFN_MIGRATE; >>> migrate->cpages++; >>> goto next; >>> } >>> page = vm_normal_page(migrate->vma, addr, pte); >>> + if (page && !is_zone_device_page(page) && >> >> I'm wondering if that check logically belongs into patch #2. > > I don't think so as it would break functionality until the below > conditionals are added - we explicitly don't want to skip > is_zone_device_page(page) == False here because that is the pages we are > trying to select. > > You could add in this: > >>> + !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) > > But then in patch 2 we know this can never be true because we've already > checked for !MIGRATE_VMA_SELECT_SYSTEM there. Ah, okay, thanks Reviewed-by: David Hildenbrand <david@redhat.com>
diff --git a/include/linux/migrate.h b/include/linux/migrate.h index 069a89e847f3..b84908debe5c 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -148,6 +148,7 @@ static inline unsigned long migrate_pfn(unsigned long pfn) enum migrate_vma_direction { MIGRATE_VMA_SELECT_SYSTEM = 1 << 0, MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1, + MIGRATE_VMA_SELECT_DEVICE_COHERENT = 1 << 2, }; struct migrate_vma { diff --git a/mm/migrate_device.c b/mm/migrate_device.c index a4847ad65da3..18bc6483f63a 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -148,15 +148,21 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, if (is_writable_device_private_entry(entry)) mpfn |= MIGRATE_PFN_WRITE; } else { - if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) - goto next; pfn = pte_pfn(pte); - if (is_zero_pfn(pfn)) { + if (is_zero_pfn(pfn) && + (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) { mpfn = MIGRATE_PFN_MIGRATE; migrate->cpages++; goto next; } page = vm_normal_page(migrate->vma, addr, pte); + if (page && !is_zone_device_page(page) && + !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) + goto next; + else if (page && is_device_coherent_page(page) && + (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) || + page->pgmap->owner != migrate->pgmap_owner)) + goto next; mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE; mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0; }